Drilling a .070" hole in the butterflies works for long duration camshafts, for example, a mechanical camshaft that has 260* or more @ .050". My 460 CID has a very moderate Iskenderian custom ground flat tappet mechanical camshaft, Int. 240* @ .050" Exh. 246* @ .050", 108* LSA with 104* ICL. In order to get my engine to idle correctly I had to re-set the secondary butterfly adjustment screw on the underside of the carburetor as well as make sure the idle transfer slot only has .025" exposure on the primary side. Works great. Cool videos.
What do you mean by reset your secondary butterflies? Were they not set straight on the throttle shaft or are you referring to setting the transfer slots on the secondary side?
@@privatename8888 The bottom side of the carburetor there is a inset screw that can be turned clock wise to open the secondary transfer slots a little more to increase the idle. Keep the primary transfer slots in the square shape or as vikingmike said. .025 exposure.
You the man, thanks for the refresher course. I'm working a 6 pack and forgot all about the transfer slot on the center at idle setting.....on all 3 carbs. I appreciate this video!
felt I had to let you know on your advice , following what you said I picked up 2 tenths and 3 miles per hr on my drag car and was really happy , keep up the great advice thank you !!
hey their some good news after making some more adjustments sunday I picked up another 1/10th of a second im speechless not surprised after 45yrs of drag racing your advice is a plus I picked up 3/10ths total and 3 miles per hr and still feel with your advice there is still a little more in it THANK YOU !!!
I've been putting off addressing a very rich condition on my Quick Fuel 650 DP with 4 corner idle air adjustment! After seeing this video I decided to add the .070" holes in the butterflies also, since I was going to have it apart. I knew I'd need to reduce the power valve size as my cam makes just 10" of vacuum, and it turned out to be a #6.5, so I also dropped it to a #4.5. Once I rejetted it, changed the power valve, and did the mod to the butterflies, it runs very clean! My throttle plates were closed fine, and didn't need to adjust them to close more. Thanks for this excellent video!!
So I tried this and it worked. 390 FE with 5psi vacuum at idle. Had overexposed transition slot and although that improved idle circuit it created stumble on transition circuit. Squared up transition slot on throttle blade and drilled 7/64 in throttle blade and the vacuum gauge needle stopped bouncing and the car runs best so far. Easy to do!
Randy, great stuff! I knew when I watched this video for the first time that I was going to learn a lot from you, and I trust what I've learned. However I'm experiencing something new, and I'm hoping you can help me with my problem. First the car: 1967 Shelby GT500 "Eleanor" #142 Holley 850 double pumper, 428CJ, 12°BTDC, 15"Hg @ 1000rpm. A year ago, my client was experiencing a "run-on" problem,.and I adjusted and addressed a lot to get to good strong running engine that didnt "run-on" after beating on it for an hour. Fast forward to 2 weeks ago. I recieve a phone call explaining that the "Shelby" won't idle, spits, bangs, and smells awful. In the past year it's been driven 20 miles, started and revved up for friends to hear then shut off(about 10 maybe more times until it wouldn't anymore). Still with the same fuel(93 octane pump gas) from a year ago with no additives I drained the fuel cell, lines, and carburetor. I installed 8 new Autolite 124's and went through the carburetor. I replaced all gaskets and the needle and seats. Starting with squared transfer slots on the primaries, no slot exposed on the secondaries, 1 and a half turns out on the primary idle screws, and 1 turn out on the secondary idle mixture screws idle speed is 1250 to 1300rpm. I have to turn the idle screw to the point just before the primary plates want to stick, primary mixture screws to 1 turn and secondary to 7/8 of a turn to get 900rpm idle speed. I don't feel comfortable with that, but I don't know if this is normal. If I turn in any mixture screw in any further the engine will idle then stall. Am I doing something wrong? Thank you in advance Randy! I hope you get to see this and you're able to help me out.
First check for vacuum leaks around the main vacuum fitting at or around intake manifold, if your throttle plates are almost closed its pulling unmetered air from some where , also check your pcv valve and hose I've seen the wrong pcv valve pull to much air and stuck or cracked pcv valve some where I believe your pulling unmetered air, some engines had a vacuum fitting that screwed into the manifold and had brake booster hose and had small little vacuum cap that would become hard and crumble, some where almost hid , you had to feel around with your fingers to find. Check everything hoses fittings and even your brake booster, if the carb is working properly and clean the problem should be a vacuum leak . Hope this helps.
@@holleycarbshowtosadvice40y90 I failed to mention that I have a 0.110" hole in each throttle plate. I suspected the PCV valve too. I pinched off the line from the back of the carburetor and the idle dropped substantially. I'm going to install and adjustable PCV valve next week. Thanks for your help Randy.
If you can lower the secondary idle any amount without sticking the plates. I know you probably already thought of this. There is different flowing pcv valves. Maybe retard ignition timing a couple degrees, other than that, may have to replace throttle plates. Good luck.
@@holleycarbshowtosadvice40y90 I backed off the secondary idle screw a 1/4 turn, installed the ME Wagner dual flow PCV valve, and made a dedicated vacuum port for the brake booster. I left timing at 10° BTDC and we went for a test rip. All good. Thanks for the replies and advice.
Thanks Randy! I’m pretty confident this is the problem with mine. When I slowly press on the throttle backing out of the driveway it wants to smother out and die at 1/8 throttle or less. If I push the throttle fast activating the pump it does fine but whe the pump isn’t involved it won’t take fuel and die. I’ve been trying to remedy this with the lower vacuum power valve but I though I’ve seen improvements I think I’ve done all I can. Time to drill holes.
Take a look at your accelerator pump again it should squirt fuel even at slow speeds , it has to function even at very light pedal movement , if not it will cause a hesitation , let me know if you need more help.
This video Finaly solved why my engine wasnt idling. It has a high duration comp cams that runs perfectly fine when steping on the gas, but when I let go of the throttle it dies because there is not enough air going into the engine, because the low engine vacuum cant pull it though.
Also try to get more initial ignition timing and if using it for the street that will help raise engine vacuum but if your drag racing it track only I would lock the distribuor timing out and that will raise your engine vacuum alot and will have a much better driveability. Hope this helps
Randy the carb im using is a mighty demon 850 cfm down leg carb and was told they are going to be faised out by holley I was looking for a billet metering block but found no good keep up the great advice
Excellent explanation, subscribed next vids should be details of hole sizes, and how to increase decrease thousands to improve a slightly RV power to hot to mild engine ,regardless of make/model. ok, a bit of a tough one, but general basic explanation would be great. 61 old fart like me needs more detailed info
Hey ill be 68 in three weeks but I quess your talking about when to drill air bypass holes and sizes from Rv cam to mild to a wild cam . Should be able to soot a video soon.
Yes the transfer slot is pulling fuel at idle and the opening of the transfer slots should be about .025 exposed with the throttle plates closed, if not the transfer slot will make the idle circuit to rich thats the first of several steps to tuning the idle circuit. I have video that explains this in detail. Let me know if I can help.
I have found that one side idels and the other side is plugged so i reve up the engen and shutt the choke realy quick and do it a couple of times and it sucks it out and now it idels and runs just fine saves me a rebuild
My pro form 750 on my 302 it has .30 on the secondary transition. Still idles at 10 afr. I upped my idle air bleeds from .70 to .77 I’m going to restrict the emulsion from.33 to .27 hopefully I will have some adjustment in my idle air screws. They’re bottomed out
How much transfer slot is exposed in your primaries and secondaries ,is it a 2 circuit or a 4 circuit idle? And do you have a racing cam , if so how much duration @ .050.
Hi Randy how can I verify if my 1850 600 cfm has a blow out protection valve? Should I not have one can my carb be modify if so can you make a video on that procedure please. Thanks Yazmin ........ Venice Beach, CA
Hello Randy thankyou for the video i noticed at 11:20 on the 1850 the secondarys where not drilled is this beacuse it has no coner idle mixture screw? Thankyou
No I got side tracked, I have a couple of videos I'm going to do and then we will finish the 1850 , sorry its taking so long , I appreciate your patience .
Great video's.. I do have a question. I'm running a 600 holley vacuum secondaries on a 1971 Ford Torino. The camshaft I put in it is really to big 515 lift 280-290 duration and 108 lsa. Somebody else built the carb, so I have no idea what was changed internally. The carb works great other than from a dead stop the secondaries don't want to open. If your rolling about 10mph it will kick in fine. I've changed the secondary to the short yellow one ( that one seems to work the best ) other than from a dead stop.. I'm pretty sure that with the cam I got my issue is more of a vacuum issue then a carb issue, but I was wondering if I could tweak on the carb and make it work instead of digging into the timing and all that.. Any info would be greatly appreciated. Keep up the great work
From my experience with carbs that have vacuum secondaries, they won't open immediately like carbs with mechanical secondaries. A double pumper for example. Using a light weight spring in the vacuum setup is probably the closest you will get to having them open sooner.
I have a problem with one idle screw adjustment makes no difference, other one screwed all the way in it dies. I'm thinking I have a blockage some where. I'm going to try a different metering block. Thanks
With your carburetor removed, remove your idle mixture screw and blow low pressure air in the mixture screw hole, air will escape out the idle air bleed an the transfer slot and the idle mixture hole, if there is a blockage you'll find it. Hope this helps.
There's three holes air bleed , transfer slots, and idle mixture hole. Look at your air bleed inside the carb throat, the carb cleaner should be spraying straight up out of the carburetor throat, thats the one that usually stops up. Hope this helps.
Write me back your list number on the choke horn of the carb and also information on the car or truck and when you accelerate hard does it backfire , try to send as much information as you can like when this problem started and what you have done so far.
@@holleycarbshowtosadvice40y90 it is full drag , 1 to 1 Holley 1050 4150 , gas...I built the carb buying parts,base,main body bowls,metering plates...no power valve....it is squared off on jets size 89....the problem I'm having is a flutter type when secondary opens
Yes and yes....ok....the flutter sound that I'm hearing is my ignorance....was not paying attention to my rev limiter....for some reason it was set at 4800....I'm just getting into power at 4500....so now that ignition is set properly I can now start over on carb tune....I appreciate everything and sure I will be getting back with you as I value your knowledge
It's not the same, when you drill the throttle plates all your doing is bypassing air pass the plates to raise the idle speed slightly and then you can lower your idle screw to close up the transfer slots. Your idle air bleeds tend to richen or lean the idle circuit, increasing the hole size leans the idle and the opposite is true to richen. Hope this helps.
Hi Randy....I wanted to ask your opinion on why my 1850 600cfm Holley makes my exhaust smell really gassy. I have a 1974 Nova 350..TH350 tranny ..6al ign .. 3.08 rear differential. if I left anything out please let me know Yazmin ..Venice Beach CA
Randy could ask better questions than me, but two easy thoughts come to mind. First is not all Holleys have power valve protection, so you may have a damaged power valve from a backfire and it needs replacement. Second is easy: make sure idle air bleeds are clean. If they aren't pulling in air, there's no emulsification of fuel prior to entering at bottom of venturi which would take a previous good tune and make it run rich if no adjustments were made - the circuit delivers pure fuel. Just my two cents on a good starting point.
that's good information , older holleys don't have power valve protection ,unless its been added. most all later model holleys have proection., flinch your a smart guy, very good information.
After following these instructions and doing this to my Holley 670 carb with vacuum secondaries. With the engine warm and the choke open. When revving up the engine with the throttle and then releasing the gas pedal, what would cause the idle to get stuck at 1400 rpm and then take 20 to 30 seconds to drop down to 900 rpm idle?
@@privatename8888 If I remember correctly, my carb idle problem was due to a vacuum leak at the base of the carburetor. Found the leak by spraying starter fluid on it during idle.
On a vacuum secondary with an electric choke, one must inspect the amount of transfer slots exposed after the carb comes off choke? Correct? I mean that while the choke is holding the primary butterflies open to enrich the fuel mixture all bets are off, are they not?
You say to shoot for 12.8-13 on a race engine, and im assuming thats thru the whole curve. My question, what idle afr should i shoot for? Just a 10:1 383 making 475 hp. It seems to me it doesnt like the leaner idle mixtures, i have it around 13.3-13.5:1 at idle and seems to like it.
I ran my drag car a little fat at idle you don't want it to stumble out of the hole and slowly lean it up some on top end. Its hard to burn a rich mixture up top. But every engine combo is a little different. Good luck
Does this information work on a older Barry Grant demon carburetor I believe I have a 625 CFM Street demon with the choke and vacuum secondaries on a small block Chevy 383
Barry Grant is a smart guy, I've never modified his own design of the holley like the demon , but his early mods of the holleys yes it will work, and probably would work on his design , they use the same kit. Hope this information helps.
Hi Randy, love the videos. On a 4412 do all of these principals apply? Also friend has a circle track car and it's been a while since he ran it. Ran and idled fine, now goes to fire it up and it won't idle. Cleaned it all out, but still won't idle. Any thoughts? Thanks.
Yes the 4412 fall under the same mods , just half a 4 barrel. The circle track carb , make sure , no vacuum leaks, most times I see this it's due to the wrong main body gasket , I don't know if you changed the gasket when cleaned it. There is so many gaskets that come with the carb kit and the wrong gasket will block the idle feed hole , Now with all that aside all you need to clean is the metering block , l'm going to do a video on a 750 do 5/15/ 20 and I will show you in the video hope this helps.
I adjusted the slots on my quick fuel dp to square but the engine wouldn't start . I had to turn the curb idle screw unward several times to get it to start. So although i set the slots right that changed when i gad to raise the idle. Dies that mean i need to drill the holes?
If your transfer slots are set properly and you don't have a leaking power valve or a flooding condition or wrong air fuel restrictor, then yes you can change the idle air bleed to a larger size to lean your idle.
On another note, some fellas at a local speed shop suggested installing a spacer and drilling out the air holes in the spacer beneath the carb rather than modifying the butterflies. Any thoughts on that idea vs. putting them directly in the butterflies?
Mark I don't know if you use a air filter or not , one advantage is all your air is being filtered , I don't believe I would want the holes in a spacer . if you can afford to buy a holley ultra they have a idle air bypass designed in them.
I know this is a older video & i have a proform 650 carb on a 302 ford gt40p heads ported single plane intake. I have looked at my transfer slots and i can turn idle screw down to get a .040 square on one front slot but the other slot is about .060 to .070 slot asking if ther is any remedy that i can do. Thanks Jim Ohio
Jim I've seen this before , there is a two part epoxy that is made to work with fuel, I've used it in intake manifolds , you can use it to repair the transfer slot very carefully. I'm not at my shop right now i will get you the information and get back to you.
@holleycarbhowto if I set my transfer slot,my idle speed is entirely to high.am I missing something simple? It’s a Holley XP Thank you for your time.Love your content
Do you know about your adjustable air bypass , it is designed into the xp ultra series carb , it's under the air cleaner stud , if you have your transfer slot set right on the primaries , secondary tranfer slot is not exposed at all , usually secondary idle screw is about one turn out from being bottomed out then adjust your idle air bypass screw under the air cleaner stud ,clockwise will lower your idle and counter clockwise will raise it , basically set your transfer slot on the primaries and adjust idle air bypass screw to your desired idle speed, then adj your idle mixture and if idle changes use your bypass to correct it ,PS don't set your secondaries up like your primaries your transfer slot will not be exposed on secondaries if they are your idle will be to high , the transfer slot adjustment only pertains to the primaries . Hope this helps.
@holleycarbhowto. I am grateful for your reply sir thank you so much for your time.I had NO CLUE about that particular adjustment 🙏 I’m excited about this carburetor again. Your content is youtube gold.
Hey also make sure no vacuum leaks on front or back of carburetor , where vacuum plugs would go and your absolutely welcome , let me know how it turns out.
I put a big cam in my FE motor the car won’t idle at all, and I got one guy telling me I need a transmission with a converter and someone telling me i need a bigger cfm then my 600. Should I try this butterfly modification first?
With engine idling, trans in park will it idle on its on or does it start up and cut off. Give me some information about your engine and your cam specs. I need your cam duration @0.50 , lobe seperation, intake center line and lift and is it flat tappet or roller. Also the size carb and did someone just rebuild it. Also compression if you have it Write me back.
@@holleycarbshowtosadvice40y90 stock 352FE with stock heads and headers just installed a comp cams 270S cam with a Edelbrock performer intake and a 600cfm Holley vacuum advance carb. Car won’t idle at all. Had 3psi of fuel while holding the gas down to make it idle so I got a bigger fuel pump. Haven’t installed yet Intake duration at .50 224 Exhaust duration at .50 224 Advertised intake and exhaust duration is 270 for both Lobe seperation 110 Flat tappet cam
Ok bud that cam should work fine, now if the holley carb has been rebuilt i wont you to remove the carb and turn it upside down and remove the philips head screws that hold the throttle plate assembly and look carefully at the gasket and see if its covering up the two outer idle circuit holes by lifting up the front corners of the gasket on the primary side of the main body. Its so easy to put the wrong gasket on and it will block the two outer holes of the idle circuit. Let me know how it turns out. This cam should work great with your engine package. Hope this helps.
@@holleycarbshowtosadvice40y90 thank you I can check in the morning I am at work for the night and I have no idea on how to set a base starting point for my secondary butterfly adjustment. Do you have a video on that? And thank you very much for responding I appreciate you
On my Holley 4160, my primary throttle plates are closed, stop screw away from the stop, as you say I have idle control w/idle mixture adjustment screw. I'm tickled, however I'm idling at 1000rpm, will drilling the plates from there now 1/16 holes (increasing) to .070-.080 raise or lower idle rpm?? Stock Ford 351w.
Chip don't leave your idle screw backed out away from the hard stop , it can cause the butterflies to stick in the throttle plate bore , always set the idle hard stop screw were the butterflies aren't touching the throttle plate bore, check your secondaries and see if you have room to lower your idle through your secondary hard stop screw, remember to leave some room between the butterfly and throttle bore were they don't bind. If your engine won't idle down lower than a thousand rpms check for vacuum leaks. Hope this helps.
Hey randy just finished watching this , my carb is very rich at idle and I am using a 260 cam , I’ve restricted the idle circuit and my mixsture screw does work because if I go to far in the car will die so maybe drilling is not my fix ,, do you think I need bigger air bleed on the idle circuit ? Mine are still brass plug so I’d have to drill and tap to make it adjustable
Darren if you got your transfer slots set right then open up your idle air bleeds and that will lean your idle circuit , don't restrict your ifr under .035 thousandths unless your after fuel mileage, just remember to do your transfer slots first and idle air bleeds last. Hope this helps.
@@holleycarbshowtosadvice40y90 Definitely helps , for some reason I never got the notification that you responded to my same question on another video , so I do apologize, you have been a tremendous help Thank you for sharing your knowledge, his is my final piece to getting my tune 💯
@@holleycarbshowtosadvice40y90 Hey randy I’m back and hoping you can help , So I brought the idle fuel restrictor back to .032 , I drilled the air bleeds and for idle my factory was .069 With bits I had I brought it to .074 on the idle air jet and my wide band still read around 12.8-132 at idle , I take it for a short ride and noticed my temp guage was getting hot , got it home pulled the plugs and they were clean with hint of white ,, not really sure if it’s lean or to hot of a plug but long story short I brought the air jet back to .069 and one thing I noticed was my car would fire right up on the .074 idle air jet going back to the .069 it cranks and some times I have to give it a rev for it to ketch ,,, not fuel , if I give it fuel like pumps with accelerator pump it makes the cranking worse ,,, it more like I need to crack the throttle hence add air ,,, I’m thinking about upping the main jets but not sure yet as I’ve tuned the bog out and car and lean spot I had seemed to go away after bringing the idle restrictor back to .032 it was at .028 I seem I can’t trust my wide band so I’m trying yo do this the old way of running it and pulling spark plugs ,,, any help would be appreciated,,, on my mind if I bring it back to .074 on iab maybe compensate by running bigger jet for the leaness ,, still not sure if it’s lean or just to hot of a plug but car is back to nice temps with the .069 air bleed I’ve spent lots of time tuning yo get bog out and lean spot so just trying my best to not have to start from scratch
Hi Randy, this is Vince from AZ I have a question do you have a video on making a big carb int a smaller one? For example how can I turn my 750 to a 650?
I been researching and some people say I have to change the main body to a 650 and everything else bolts on. Other people say I just need to change the metering block to a 650
I have a 289 sbf w/ a big cam and it idles between 1200-1400 rpm. Anything lower than that and engine stalls. Any idea how I can bring down the idle between 1000-1200 rpm? Thanks in advance 🙂
My nova was mostly used as a drag car, but when I locked out my distributor advance the engine idled so much better. There are several ways to do this, a full lock out or recurve the distributor advance, recurving the advance means for instance you might want to set your ignition timing to 26 degrees initially and bring 8 or 10 degrees in mechanically for your total ignition advance of maybe 34 to 36 degrees. You will probably need a start retard box to retard timing while cranking. I ran MSD ignition with a start retard box on mine but other companies offer the same thing. Hope this helps
It is common to have the IFR below the fuel level. It sounds like you are suggesting the IFR be installed up top. I realize it is a bit more difficult to thread the lower position. But you might want to suggest persons research the differences in performance. Old school carbs are lower position while current offerings IFR are up top.
@ minute 5:37, In the idle port on the main body I have a screwed in a fuel restrictor but it is still running too rich. Would it still be ok to put another fuel restrictor in the metering block?
Really the hole idea about putting the fuel restrictor in the main body is to hide the modification being made, and the fuel restrictor should not be changed until you set the transfer slots and then work with the idle air bleeds, increasing the idle air bleed size will lean the idle circuit usually this will be all thats needed to correct the idle circuit. Let me know if you have any questions..
If I quickly stab the gas on my holley and let the engine settle back down to idle it will idle slowly. If I slowly press the gas the engine will idle high. Every holley i have ever owned does this. What's the reason?
I need more information , is your engine stock, what type of distributor is it vacuum advance and mechanical advance (stock) and if it is stock where is your vacuum hose from distributor hooked to the carburetor, either to the metering block or throttle plate? Besides checking for linkage for binding or if it has a choke fast idle cam screw set wrong or a vacuum leak can cause this to. Give me a general breakdown of your engine and check any thing that applies that I mentioned .Let me know .
@@holleycarbshowtosadvice40y90 thank for the reply. every holley I have ever owned on multiple engines has done this. 2.8l v6 with a vc 390cfm and vacuum advance distributor. 350 with a 3310 750 CV/ demon 650 vc / mighty demon 750 annular booster that came factory without a chock. Maybe I'll shoot a video for you when the weather gets better thanks.
Iv looked ever where for information on 1050 4500 dominator. I tried to run power vales. This not working on mine.on ly plugs work for me if you have info please post to keep some one else from a hard ache.
My friend I know its been a long time ago when you wrote me but there was a problem with my you tube channel and something changed and I'm seeing all these comments from years ago some back then just did not show up i apologize and will be glad to answer your questions just need more information, list# number and any thing you can tell what you tryed on it. Take care.
Cam also has .300 lift at intake and .450 lift at exhaust, with 1.6 roller rockers… just want to make sure this is the problem I’m having before I end up drilling holes
There's no way to tell you exactly but low vacuum is what causes this problem, all we are doing is bypassing air past your throttle plates, try raising your secondary idle speed and lowering your primary idle speed to close up your transfer slots, sometimes this will help or even fix the problem. Make sure to adjust your idle mixture after you change your idle settings. This may work for you if your cam is 274 degrees of advertised duration. Hope this helps.
@@holleycarbshowtosadvice40y90it’s a 383 stroker. I’m getting about 13 hg vacuum. It’s a Holley 4160, 750 cfm. I can get the car to idle great at 750 rpm with the idle stop screw all the way out. Car runs with the primary idle mixture screws all the way in. Still super rich and on the verge of fouling plugs. Just can’t get the thing to lean out even a little.
Ok if the power valve is leaking it will run real rich with both mixture screws turned all the way in, and if there's to much transfer slot open same thing. This is the two most basic things that will cause your concern. Hope this helps.
here is a good question. what happens when you got the holes drilled from a .093 drill all the way up to a .120 drill and it still wont close the transfer slot. the idle mixture screws will kill the engine. but at about 5 turns out. still idles high and now returns to the high idle slowly. are my holes still not big enough? seams like its wants to run away when i rev it up. please answer back. could timing be a factor
Sounds like you have a vacuum leak,, also need to know if your engine has a racing cam, the procedure of drilling the throttle plate bypass holes is more for racing engines , I need all your information to try and help you . Like Is this a new engine build , engine specs etc, but sounds like maybe vacuum leak .
@@holleycarbshowtosadvice40y90 could it be internal in the carb? i have sprayed and sprayed, the intake the base of the carb the entire carb with no change to idle of the way it runs. however i did use water cause i had no carb cleaner at the time. will this make a differance?
@@holleycarbshowtosadvice40y90 yes it seems to have good power does REV through the entire RPM range when I first started doing this it had the stumble and everything that you described when drilling the holes I got to stumble to go away but it still wouldn't idle down let's say 800 to 700 RPM so the stumble is gone but it still won't idle below a thousand RPM and there's still more than 30 to 70 thousands of the transfer slot exposed and if I try to turn the mixture screw in more than five turns it'll die so it's almost like a lean condition right at this point
That question is hard to answer , because there is so many things that factor in , it would be best to go by the amount of idle vacuum , normal idle vacuum is around 17 to 18 inches. I would say some where around 14 inches or lower , usually a good sign is you loose control of your idle mixture screws.hope this helps.
I have a quickfuel brawler 650 double pumper. the transferslots are adjusted but do I need to open the secondaries butterflies evenly open with the primaries butterflies or can I just adjust the idle speed with the secondaries? My cruising AFR is about 14.5-15.5. But if I lean out my idle AFR my cruise AFR is to lean . What can I do about it? Thanks for the vids
It all comes down to how big a cam your running, if your cam is small you can usually get away with setting your transfer slots correctly and then adjusting your idle with your secondaries, but with a big cam you usually have to drill air bypass holes to lean your idle mixture and work with your idle air bleeds if needed.
For your second question when you lean your idle mixture with the idle fuel restrictors you also lean your transfer slots which will cause your cruise afr to go lean. So try leaning your idle with your idle air bleeds if they are changeable, 003 thousandths at a time, and put your idle fuel restictor back to stock and see how that works for you. Hope this helps.
@@holleycarbshowtosadvice40y90 Quickfuel brawler 650DP and 331 stroker 10.0-10.5 compression and cam 230/230 at 50 and 290/290. Dual plane intake. my ifr are still original at 32. Airbleeds also. Prim jets 70 original and sec jets from 74 to 79. Half THROTLLE fuel curve is flat at 12.3-12.7. Full THROTLLE goes from rich 10.5 to 13.5. My half throtlle is good but I need to adres the rich low rpm secondaries to high rpm lean And my idle is 13.2 and will idle better at 13.7 but then cruise is to lean at 16. If I put cruise with idle screws to 15.4 then idle is rich at 13
You can't adjust the idle mixture screws for cruise that won't work, the idle mixture screws are for adjusting your idle afr, then when your at cruise your transfer slots ad fuel, then I tune with ifr and idle speed air bleed and float level adjustment for cruise their is a lot of variables but I start tuning from idle then cruise to mid throttle to wot. Hope this helps.
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This is one of the best video I’ve ever watched on TH-cam. So easy to understand. Thank you.
I'm glad you enjoyed it, please write me if i can help you. Thanks
I’ve been working on these for years and you gave me more information than I ever got on a Holley Carburetor. Thank you!!
David I'm happy to be of help. And remember if I can help let me know. Have a good one.
Drilling a .070" hole in the butterflies works for long duration camshafts, for example, a mechanical camshaft that has 260* or more @ .050". My 460 CID has a very moderate Iskenderian custom ground flat tappet mechanical camshaft, Int. 240* @ .050" Exh. 246* @ .050", 108* LSA with 104* ICL. In order to get my engine to idle correctly I had to re-set the secondary butterfly adjustment screw on the underside of the carburetor as well as make sure the idle transfer slot only has .025" exposure on the primary side. Works great. Cool videos.
What do you mean by reset your secondary butterflies? Were they not set straight on the throttle shaft or are you referring to setting the transfer slots on the secondary side?
@@privatename8888 The bottom side of the carburetor there is a inset screw that can be turned clock wise to open the secondary transfer slots a little more to increase the idle. Keep the primary transfer slots in the square shape or as vikingmike said. .025 exposure.
How did you measure for 0.25" what did you use as a measuring tool?
Did you make something to use?
@@privatename8888 Just use the square transfer slot method. It's easier that way.
Thanks for watching
Probably the best and most understandable explanations I've ever heard. Great job! Thank you!
Thanks
You the man, thanks for the refresher course. I'm working a 6 pack and forgot all about the transfer slot on the center at idle setting.....on all 3 carbs. I appreciate this video!
Thanks alot
@@holleycarbshowtosadvice40y90
Excellent videos..........Do you know anything about reading old sun machine oscill scopes
felt I had to let you know on your advice , following what you said I picked up 2 tenths and 3 miles per hr on my drag car and was really happy , keep up the great advice thank you !!
Carl that's great , your welcome and hope these videos helped
hey their some good news after making some more adjustments sunday I picked up another 1/10th of a second im speechless not surprised after 45yrs of drag racing your advice is a plus I picked up 3/10ths total and 3 miles per hr and still feel with your advice there is still a little more in it THANK YOU !!!
I've been putting off addressing a very rich condition on my Quick Fuel 650 DP with 4 corner idle air adjustment! After seeing this video I decided to add the .070" holes in the butterflies also, since I was going to have it apart. I knew I'd need to reduce the power valve size as my cam makes just 10" of vacuum, and it turned out to be a #6.5, so I also dropped it to a #4.5.
Once I rejetted it, changed the power valve, and did the mod to the butterflies, it runs very clean! My throttle plates were closed fine, and didn't need to adjust them to close more.
Thanks for this excellent video!!
Marlin glad I could help, you have a merry christmas.
This is the BEST instruction i have ever had,Thank You !!!!
Glad to help
So I tried this and it worked. 390 FE with 5psi vacuum at idle. Had overexposed transition slot and although that improved idle circuit it created stumble on transition circuit. Squared up transition slot on throttle blade and drilled 7/64 in throttle blade and the vacuum gauge needle stopped bouncing and the car runs best so far. Easy to do!
That's great
The best explanation I've seen so far on this adjustment! Thank you!
I appreciate it.
Randy, great stuff! I knew when I watched this video for the first time that I was going to learn a lot from you, and I trust what I've learned. However I'm experiencing something new, and I'm hoping you can help me with my problem.
First the car:
1967 Shelby GT500 "Eleanor" #142
Holley 850 double pumper, 428CJ, 12°BTDC, 15"Hg @ 1000rpm.
A year ago, my client was experiencing a "run-on" problem,.and I adjusted and addressed a lot to get to good strong running engine that didnt "run-on" after beating on it for an hour.
Fast forward to 2 weeks ago. I recieve a phone call explaining that the "Shelby" won't idle, spits, bangs, and smells awful. In the past year it's been driven 20 miles, started and revved up for friends to hear then shut off(about 10 maybe more times until it wouldn't anymore). Still with the same fuel(93 octane pump gas) from a year ago with no additives
I drained the fuel cell, lines, and carburetor. I installed 8 new Autolite 124's and went through the carburetor. I replaced all gaskets and the needle and seats.
Starting with squared transfer slots on the primaries, no slot exposed on the secondaries, 1 and a half turns out on the primary idle screws, and 1 turn out on the secondary idle mixture screws idle speed is 1250 to 1300rpm.
I have to turn the idle screw to the point just before the primary plates want to stick, primary mixture screws to 1 turn and secondary to 7/8 of a turn to get 900rpm idle speed. I don't feel comfortable with that, but I don't know if this is normal.
If I turn in any mixture screw in any further the engine will idle then stall. Am I doing something wrong?
Thank you in advance Randy! I hope you get to see this and you're able to help me out.
First check for vacuum leaks around the main vacuum fitting at or around intake manifold, if your throttle plates are almost closed its pulling unmetered air from some where , also check your pcv valve and hose I've seen the wrong pcv valve pull to much air and stuck or cracked pcv valve some where I believe your pulling unmetered air, some engines had a vacuum fitting that screwed into the manifold and had brake booster hose and had small little vacuum cap that would become hard and crumble, some where almost hid , you had to feel around with your fingers to find. Check everything hoses fittings and even your brake booster, if the carb is working properly and clean the problem should be a vacuum leak . Hope this helps.
@@holleycarbshowtosadvice40y90 I failed to mention that I have a 0.110" hole in each throttle plate.
I suspected the PCV valve too. I pinched off the line from the back of the carburetor and the idle dropped substantially. I'm going to install and adjustable PCV valve next week. Thanks for your help Randy.
If you can lower the secondary idle any amount without sticking the plates. I know you probably already thought of this. There is different flowing pcv valves. Maybe retard ignition timing a couple degrees, other than that, may have to replace throttle plates. Good luck.
@@holleycarbshowtosadvice40y90 I backed off the secondary idle screw a 1/4 turn, installed the ME Wagner dual flow PCV valve, and made a dedicated vacuum port for the brake booster. I left timing at 10° BTDC and we went for a test rip. All good. Thanks for the replies and advice.
I love how well described and explained these videos are.
Thank you
Thanks Randy! I’m pretty confident this is the problem with mine. When I slowly press on the throttle backing out of the driveway it wants to smother out and die at 1/8 throttle or less. If I push the throttle fast activating the pump it does fine but whe the pump isn’t involved it won’t take fuel and die. I’ve been trying to remedy this with the lower vacuum power valve but I though I’ve seen improvements I think I’ve done all I can. Time to drill holes.
Take a look at your accelerator pump again it should squirt fuel even at slow speeds , it has to function even at very light pedal movement , if not it will cause a hesitation , let me know if you need more help.
My new favorite channel.
Thanks.
Your videos are VERY informative. Thanks.
Glad you like them!
This video is amazing appreciate all the information.
Thank you.
Thanks to share your knowledge
Thank for watching.
This video Finaly solved why my engine wasnt idling. It has a high duration comp cams that runs perfectly fine when steping on the gas, but when I let go of the throttle it dies because there is not enough air going into the engine, because the low engine vacuum cant pull it though.
Having the same issue on my car going try implementing his advice and see if it helps
Also try to get more initial ignition timing and if using it for the street that will help raise engine vacuum but if your drag racing it track only I would lock the distribuor timing out and that will raise your engine vacuum alot and will have a much better driveability. Hope this helps
Randy the carb im using is a mighty demon 850 cfm down leg carb and was told they are going to be faised out by holley I was looking for a billet metering block but found no good keep up the great advice
Thanks
Excellent explanation, subscribed next vids should be details of hole sizes, and how to increase decrease thousands to improve a slightly RV power to hot to mild engine ,regardless of make/model. ok, a bit of a tough one, but general basic explanation would be great. 61 old fart like me needs more detailed info
Hey ill be 68 in three weeks but I quess your talking about when to drill air bypass holes and sizes from Rv cam to mild to a wild cam . Should be able to soot a video soon.
@@holleycarbshowtosadvice40y90 thank u old man..lol..dang i feel young now. :)
@ minute 5:16 "the transfer slot is pulling fuel out here." Does fuel actually come out of the transfer slot? thank you so much for these videos!!!
Yes the transfer slot is pulling fuel at idle and the opening of the transfer slots should be about .025 exposed with the throttle plates closed, if not the transfer slot will make the idle circuit to rich thats the first of several steps to tuning the idle circuit. I have video that explains this in detail. Let me know if I can help.
nicely done
Thank you.
Good video my brother
Thanks again
You are a life saver. Thank you!
Thank you for watching
Sir You need to open up a class let me know when what time and where and I will be there sitting in the front seat...
Thank you.
I have found that one side idels and the other side is plugged so i reve up the engen and shutt the choke realy quick and do it a couple of times and it sucks it out and now it idels and runs just fine saves me a rebuild
10/4
Fantastic.
Thanks
My pro form 750 on my 302 it has .30 on the secondary transition. Still idles at 10 afr. I upped my idle air bleeds from .70 to .77 I’m going to restrict the emulsion from.33 to .27 hopefully I will have some adjustment in my idle air screws. They’re bottomed out
How much transfer slot is exposed in your primaries and secondaries ,is it a 2 circuit or a 4 circuit idle? And do you have a racing cam , if so how much duration @ .050.
@@holleycarbshowtosadvice40y90 it is a B cam from a ford, the transfer slots on each primary and secondary are within spec .20-.40 thou open on each.
4 corner idle, my first one. I thought 2 was hard to maintain, 4 is insane lol
Ok if your transfer slots are correct, then some where you have unmetered fuel , with a 10 afr.
Hi Randy how can I verify if my 1850 600 cfm has a blow out protection valve? Should I not have one can my carb be modify if so can you make a video on that procedure please.
Thanks
Yazmin ........ Venice Beach, CA
yes if you don't have one , its easy to add one , I will try to make a video soon.
Hello Randy thankyou for the video i noticed at 11:20 on the 1850 the secondarys where not drilled is this beacuse it has no coner idle mixture screw? Thankyou
No I got side tracked, I have a couple of videos I'm going to do and then we will finish the 1850 , sorry its taking so long , I appreciate your patience .
Great video's.. I do have a question. I'm running a 600 holley vacuum secondaries on a 1971 Ford Torino. The camshaft I put in it is really to big 515 lift 280-290 duration and 108 lsa. Somebody else built the carb, so I have no idea what was changed internally. The carb works great other than from a dead stop the secondaries don't want to open. If your rolling about 10mph it will kick in fine. I've changed the secondary to the short yellow one ( that one seems to work the best ) other than from a dead stop.. I'm pretty sure that with the cam I got my issue is more of a vacuum issue then a carb issue, but I was wondering if I could tweak on the carb and make it work instead of digging into the timing and all that.. Any info would be greatly appreciated. Keep up the great work
From my experience with carbs that have vacuum secondaries, they won't open immediately like carbs with mechanical secondaries. A double pumper for example. Using a light weight spring in the vacuum setup is probably the closest you will get to having them open sooner.
There not designed to come in from a dead stop if they did the engine would bog, with a double pumper thats definitely possible.
I have a problem with one idle screw adjustment makes no difference, other one screwed all the way in it dies. I'm thinking I have a blockage some where. I'm going to try a different metering block. Thanks
With your carburetor removed, remove your idle mixture screw and blow low pressure air in the mixture screw hole, air will escape out the idle air bleed an the transfer slot and the idle mixture hole, if there is a blockage you'll find it. Hope this helps.
@@holleycarbshowtosadvice40y90 I pulled the air screw and sprayed carb cleaner with the little straw and it wetted the butterfly but still no luck.?
There's three holes air bleed , transfer slots, and idle mixture hole. Look at your air bleed inside the carb throat, the carb cleaner should be spraying straight up out of the carburetor throat, thats the one that usually stops up. Hope this helps.
Iv got a holly 4160 it cranks and idles good but when i get in and put it in gear and acelerate it just creaps along even if i floorboard it
Write me back your list number on the choke horn of the carb and also information on the car or truck and when you accelerate hard does it backfire , try to send as much information as you can like when this problem started and what you have done so far.
I was wondering about secondary transfer slot adjustment on an aftermarket base
Kevin most secondary transfer slots are not exposed at idle , need all information on carb.
@@holleycarbshowtosadvice40y90 it is full drag , 1 to 1 Holley 1050 4150 , gas...I built the carb buying parts,base,main body bowls,metering plates...no power valve....it is squared off on jets size 89....the problem I'm having is a flutter type when secondary opens
Kevin do you have jet extensions in the rear bowl , also nitrophyl notched floats ?
Yes and yes....ok....the flutter sound that I'm hearing is my ignorance....was not paying attention to my rev limiter....for some reason it was set at 4800....I'm just getting into power at 4500....so now that ignition is set properly I can now start over on carb tune....I appreciate everything and sure I will be getting back with you as I value your knowledge
Thanks and good luck
Is drilling the throttle plates the same as changing the idle air bleeds on a Holley 750 hp
It's not the same, when you drill the throttle plates all your doing is bypassing air pass the plates to raise the idle speed slightly and then you can lower your idle screw to close up the transfer slots. Your idle air bleeds tend to richen or lean the idle circuit, increasing the hole size leans the idle and the opposite is true to richen. Hope this helps.
Hi Randy....I wanted to ask your opinion on why my 1850 600cfm Holley makes my exhaust smell really gassy. I have a 1974 Nova 350..TH350 tranny ..6al ign .. 3.08 rear differential. if I left anything out please let me know
Yazmin ..Venice Beach CA
Randy could ask better questions than me, but two easy thoughts come to mind. First is not all Holleys have power valve protection, so you may have a damaged power valve from a backfire and it needs replacement. Second is easy: make sure idle air bleeds are clean. If they aren't pulling in air, there's no emulsification of fuel prior to entering at bottom of venturi which would take a previous good tune and make it run rich if no adjustments were made - the circuit delivers pure fuel. Just my two cents on a good starting point.
do you have a racing camshaft , if so I need specs on cam and engine idle vacuum if possible
that's good information , older holleys don't have power valve protection ,unless its been added. most all later model holleys have proection., flinch your a smart guy, very good information.
Thank you. Great teacher
Thanks
After following these instructions and doing this to my Holley 670 carb with vacuum secondaries. With the engine warm and the choke open. When revving up the engine with the throttle and then releasing the gas pedal, what would cause the idle to get stuck at 1400 rpm and then take 20 to 30 seconds to drop down to 900 rpm idle?
I'm having a similar issue mine stays high longer
@@privatename8888 If I remember correctly, my carb idle problem was due to a vacuum leak at the base of the carburetor. Found the leak by spraying starter fluid on it during idle.
Could be a vacuum leak or butterflies sticking or not centered.
On a vacuum secondary with an electric choke, one must inspect the amount of transfer slots exposed after the carb comes off choke? Correct? I mean that while the choke is holding the primary butterflies open to enrich the fuel mixture all bets are off, are they not?
correct. choke off and engine at operating temp and timing set properly. good job
You say to shoot for 12.8-13 on a race engine, and im assuming thats thru the whole curve. My question, what idle afr should i shoot for? Just a 10:1 383 making 475 hp. It seems to me it doesnt like the leaner idle mixtures, i have it around 13.3-13.5:1 at idle and seems to like it.
I ran my drag car a little fat at idle you don't want it to stumble out of the hole and slowly lean it up some on top end. Its hard to burn a rich mixture up top. But every engine combo is a little different. Good luck
Does this information work on a older Barry Grant demon carburetor I believe I have a 625 CFM Street demon with the choke and vacuum secondaries on a small block Chevy 383
Barry Grant is a smart guy, I've never modified his own design of the holley like the demon , but his early mods of the holleys yes it will work, and probably would work on his design , they use the same kit. Hope this information helps.
Hi Randy, love the videos. On a 4412 do all of these principals apply? Also friend has a circle track car and it's been a while since he ran it. Ran and idled fine, now goes to fire it up and it won't idle. Cleaned it all out, but still won't idle. Any thoughts? Thanks.
Yes the 4412 fall under the same mods , just half a 4 barrel. The circle track carb , make sure , no vacuum leaks, most times I see this it's due to the wrong main body gasket , I don't know if you changed the gasket when cleaned it. There is so many gaskets that come with the carb kit and the wrong gasket will block the idle feed hole , Now with all that aside all you need to clean is the metering block , l'm going to do a video on a 750 do 5/15/ 20 and I will show you in the video hope this helps.
I adjusted the slots on my quick fuel dp to square but the engine wouldn't start . I had to turn the curb idle screw unward several times to get it to start. So although i set the slots right that changed when i gad to raise the idle. Dies that mean i need to drill the holes?
Yes I drill the holes to raise the idle.
Could a rich condition on the idle screw circuit be addressed with larger idle air bleeds? What would be the result?
If your transfer slots are set properly and you don't have a leaking power valve or a flooding condition or wrong air fuel restrictor, then yes you can change the idle air bleed to a larger size to lean your idle.
On another note, some fellas at a local speed shop suggested installing a spacer and drilling out the air holes in the spacer beneath the carb rather than modifying the butterflies. Any thoughts on that idea vs. putting them directly in the butterflies?
Mark I don't know if you use a air filter or not , one advantage is all your air is being filtered , I don't believe I would want the holes in a spacer . if you can afford to buy a holley ultra they have a idle air bypass designed in them.
I know this is a older video & i have a proform 650 carb on a 302 ford gt40p heads ported single plane intake. I have looked at my transfer slots and i can turn idle screw down to get a .040 square on one front slot but the other slot is about .060 to .070 slot asking if ther is any remedy that i can do. Thanks Jim Ohio
Jim I've seen this before , there is a two part epoxy that is made to work with fuel, I've used it in intake manifolds , you can use it to repair the transfer slot very carefully. I'm not at my shop right now i will get you the information and get back to you.
@holleycarbhowto
if I set my transfer slot,my idle speed is entirely to high.am I missing something simple? It’s a Holley XP Thank you for your time.Love your content
Do you know about your adjustable air bypass , it is designed into the xp ultra series carb , it's under the air cleaner stud , if you have your transfer slot set right on the primaries , secondary tranfer slot is not exposed at all , usually secondary idle screw is about one turn out from being bottomed out then adjust your idle air bypass screw under the air cleaner stud ,clockwise will lower your idle and counter clockwise will raise it , basically set your transfer slot on the primaries and adjust idle air bypass screw to your desired idle speed, then adj your idle mixture and if idle changes use your bypass to correct it ,PS don't set your secondaries up like your primaries your transfer slot will not be exposed on secondaries if they are your idle will be to high , the transfer slot adjustment only pertains to the primaries . Hope this helps.
@holleycarbhowto. I am grateful for your reply sir thank you so much for your time.I had NO CLUE about that particular adjustment 🙏 I’m excited about this carburetor again. Your content is youtube gold.
Hey also make sure no vacuum leaks on front or back of carburetor , where vacuum plugs would go and your absolutely welcome , let me know how it turns out.
Holley Carbs: How To's & Advice ,40 yrs of exp. You’ve been more than helpful,thank you so much
I put a big cam in my FE motor the car won’t idle at all, and I got one guy telling me I need a transmission with a converter and someone telling me i need a bigger cfm then my 600. Should I try this butterfly modification first?
With engine idling, trans in park will it idle on its on or does it start up and cut off. Give me some information about your engine and your cam specs. I need your cam duration @0.50 , lobe seperation, intake center line and lift and is it flat tappet or roller. Also the size carb and did someone just rebuild it. Also compression if you have it Write me back.
@@holleycarbshowtosadvice40y90 stock 352FE with stock heads and headers just installed a comp cams 270S cam with a Edelbrock performer intake and a 600cfm Holley vacuum advance carb. Car won’t idle at all. Had 3psi of fuel while holding the gas down to make it idle so I got a bigger fuel pump. Haven’t installed yet
Intake duration at .50 224
Exhaust duration at .50 224
Advertised intake and exhaust duration is 270 for both
Lobe seperation 110
Flat tappet cam
@@holleycarbshowtosadvice40y90 stock compression 9:1 and that’s what the cam is rated for and I also did the upgraded springs
Ok bud that cam should work fine, now if the holley carb has been rebuilt i wont you to remove the carb and turn it upside down and remove the philips head screws that hold the throttle plate assembly and look carefully at the gasket and see if its covering up the two outer idle circuit holes by lifting up the front corners of the gasket on the primary side of the main body. Its so easy to put the wrong gasket on and it will block the two outer holes of the idle circuit. Let me know how it turns out. This cam should work great with your engine package. Hope this helps.
@@holleycarbshowtosadvice40y90 thank you I can check in the morning I am at work for the night and I have no idea on how to set a base starting point for my secondary butterfly adjustment. Do you have a video on that? And thank you very much for responding I appreciate you
On my Holley 4160, my primary throttle plates are closed, stop screw away from the stop, as you say I have idle control w/idle mixture adjustment screw. I'm tickled, however I'm idling at 1000rpm, will drilling the plates from there now 1/16 holes (increasing) to .070-.080 raise or lower idle rpm?? Stock Ford 351w.
Chip don't leave your idle screw backed out away from the hard stop , it can cause the butterflies to stick in the throttle plate bore , always set the idle hard stop screw were the butterflies aren't touching the throttle plate bore, check your secondaries and see if you have room to lower your idle through your secondary hard stop screw, remember to leave some room between the butterfly and throttle bore were they don't bind. If your engine won't idle down lower than a thousand rpms check for vacuum leaks. Hope this helps.
Hey randy just finished watching this , my carb is very rich at idle and I am using a 260 cam , I’ve restricted the idle circuit and my mixsture screw does work because if I go to far in the car will die so maybe drilling is not my fix ,, do you think I need bigger air bleed on the idle circuit ?
Mine are still brass plug so I’d have to drill and tap to make it adjustable
Darren if you got your transfer slots set right then open up your idle air bleeds and that will lean your idle circuit , don't restrict your ifr under .035 thousandths unless your after fuel mileage, just remember to do your transfer slots first and idle air bleeds last. Hope this helps.
@@holleycarbshowtosadvice40y90
Definitely helps , for some reason I never got the notification that you responded to my same question on another video , so I do apologize, you have been a tremendous help
Thank you for sharing your knowledge, his is my final piece to getting my tune 💯
No problem, let me know if I can help. Take care.
@@holleycarbshowtosadvice40y90
Hey randy I’m back and hoping you can help ,
So I brought the idle fuel restrictor back to .032 , I drilled the air bleeds and for idle my factory was .069
With bits I had I brought it to .074 on the idle air jet and my wide band still read around 12.8-132 at idle , I take it for a short ride and noticed my temp guage was getting hot , got it home pulled the plugs and they were clean with hint of white ,, not really sure if it’s lean or to hot of a plug but long story short I brought the air jet back to .069 and one thing I noticed was my car would fire right up on the .074 idle air jet going back to the .069 it cranks and some times I have to give it a rev for it to ketch ,,, not fuel , if I give it fuel like pumps with accelerator pump it makes the cranking worse ,,, it more like I need to crack the throttle hence add air ,,, I’m thinking about upping the main jets but not sure yet as I’ve tuned the bog out and car and lean spot I had seemed to go away after bringing the idle restrictor back to .032 it was at .028
I seem I can’t trust my wide band so I’m trying yo do this the old way of running it and pulling spark plugs ,,, any help would be appreciated,,, on my mind if I bring it back to .074 on iab maybe compensate by running bigger jet for the leaness ,, still not sure if it’s lean or just to hot of a plug but car is back to nice temps with the .069 air bleed
I’ve spent lots of time tuning yo get bog out and lean spot so just trying my best to not have to start from scratch
Hi Randy, this is Vince from AZ
I have a question do you have a video on making a big carb int a smaller one? For example how can I turn my 750 to a 650?
I'm not sure if your talking about leaning out a 750 or converting it to a 650?
Thank you for responding back, yes I want to lean it out to run on my 35O
I been researching and some people say I have to change the main body to a 650 and everything else bolts on. Other people say I just need to change the metering block to a 650
And last change the jets on the primary and add plugs to the transfer ports.
My last resort it to ask an expert.
I have a 289 sbf w/ a big cam and it idles between 1200-1400 rpm. Anything lower than that and engine stalls. Any idea how I can bring down the idle between 1000-1200 rpm? Thanks in advance 🙂
My nova was mostly used as a drag car, but when I locked out my distributor advance the engine idled so much better. There are several ways to do this, a full lock out or recurve the distributor advance, recurving the advance means for instance you might want to set your ignition timing to 26 degrees initially and bring 8 or 10 degrees in mechanically for your total ignition advance of maybe 34 to 36 degrees. You will probably need a start retard box to retard timing while cranking. I ran MSD ignition with a start retard box on mine but other companies offer the same thing. Hope this helps
@@holleycarbshowtosadvice40y90 Thanks for the tip. Will try this out and let you know result 🙂
It is common to have the IFR below the fuel level. It sounds like you are suggesting the IFR be installed up top. I realize it is a bit more difficult to thread the lower position. But you might want to suggest persons research the differences in performance. Old school carbs are lower position while current offerings IFR are up top.
Generally i move my ifr's up top . What's your opinion on where to locate the idle feed restrictors and why.
i cant stop my motor running on { dieseling ] can this mod help ? ive changed carbs even , and it still does it .
No you need an anti dieseling solenoid let me get all the information and get back to you.
Go to my video , anti dieseling and A,/C compensator that should fix it . If you have any problem let me know.
@ minute 5:37, In the idle port on the main body I have a screwed in a fuel restrictor but it is still running too rich. Would it still be ok to put another fuel restrictor in the metering block?
Really the hole idea about putting the fuel restrictor in the main body is to hide the modification being made, and the fuel restrictor should not be changed until you set the transfer slots and then work with the idle air bleeds, increasing the idle air bleed size will lean the idle circuit usually this will be all thats needed to correct the idle circuit. Let me know if you have any questions..
If I quickly stab the gas on my holley and let the engine settle back down to idle it will idle slowly. If I slowly press the gas the engine will idle high. Every holley i have ever owned does this. What's the reason?
And thanks for all the great videos btw
I need more information , is your engine stock, what type of distributor is it vacuum advance and mechanical advance (stock) and if it is stock where is your vacuum hose from distributor hooked to the carburetor, either to the metering block or throttle plate? Besides checking for linkage for binding or if it has a choke fast idle cam screw set wrong or a vacuum leak can cause this to. Give me a general breakdown of your engine and check any thing that applies that I mentioned .Let me know .
@@holleycarbshowtosadvice40y90 thank for the reply. every holley I have ever owned on multiple engines has done this. 2.8l v6 with a vc 390cfm and vacuum advance distributor. 350 with a 3310 750 CV/ demon 650 vc / mighty demon 750 annular booster that came factory without a chock. Maybe I'll shoot a video for you when the weather gets better thanks.
got a 1050 dominator is the set up on that be the same on all Holley im not get no difference out of the when I adjust the ideal adjustment
The idle adjustment is the same
Iv looked ever where for information on 1050 4500 dominator. I tried to run power vales. This not working on mine.on ly plugs work for me if you have info please post to keep some one else from a hard ache.
My friend I know its been a long time ago when you wrote me but there was a problem with my you tube channel and something changed and I'm seeing all these comments from years ago some back then just did not show up i apologize and will be glad to answer your questions just need more information, list# number and any thing you can tell what you tryed on it. Take care.
At what amount of cam duration does this become required? I have 274 duration and have been having these problems, is it time to get the drill out?
Cam also has .300 lift at intake and .450 lift at exhaust, with 1.6 roller rockers… just want to make sure this is the problem I’m having before I end up drilling holes
There's no way to tell you exactly but low vacuum is what causes this problem, all we are doing is bypassing air past your throttle plates, try raising your secondary idle speed and lowering your primary idle speed to close up your transfer slots, sometimes this will help or even fix the problem. Make sure to adjust your idle mixture after you change
your idle settings. This may work for you if your cam is 274 degrees of advertised duration. Hope this helps.
@@holleycarbshowtosadvice40y90it’s a 383 stroker. I’m getting about 13 hg vacuum. It’s a Holley 4160, 750 cfm. I can get the car to idle great at 750 rpm with the idle stop screw all the way out. Car runs with the primary idle mixture screws all the way in. Still super rich and on the verge of fouling plugs. Just can’t get the thing to lean out even a little.
It’s like the primary idle mixture screws do nothing, the secondary’s change the vacuum and idle though…
Ok if the power valve is leaking it will run real rich with both mixture screws turned all the way in, and if there's to much transfer slot open same thing. This is the two most basic things that will cause your concern. Hope this helps.
here is a good question. what happens when you got the holes drilled from a .093 drill all the way up to a .120 drill and it still wont close the transfer slot. the idle mixture screws will kill the engine. but at about 5 turns out. still idles high and now returns to the high idle slowly. are my holes still not big enough? seams like its wants to run away when i rev it up. please answer back. could timing be a factor
Sounds like you have a vacuum leak,, also need to know if your engine has a racing cam, the procedure of drilling the throttle plate bypass holes is more for racing engines , I need all your information to try and help you . Like Is this a new engine build , engine specs etc, but sounds like maybe vacuum leak .
@@holleycarbshowtosadvice40y90 could it be internal in the carb? i have sprayed and sprayed, the intake the base of the carb the entire carb with no change to idle of the way it runs. however i did use water cause i had no carb cleaner at the time. will this make a differance?
@@holleycarbshowtosadvice40y90 and it is a very big cam. on a vacuum gauge i only get 5-7 inches of mercury it does flutter though and is inconsistent
Does the motor seem to have good power or does it seem to be way down on power , and is this a new build.
@@holleycarbshowtosadvice40y90 yes it seems to have good power does REV through the entire RPM range when I first started doing this it had the stumble and everything that you described when drilling the holes I got to stumble to go away but it still wouldn't idle down let's say 800 to 700 RPM so the stumble is gone but it still won't idle below a thousand RPM and there's still more than 30 to 70 thousands of the transfer slot exposed and if I try to turn the mixture screw in more than five turns it'll die so it's almost like a lean condition right at this point
Good video👍🏻
Thanks
At what duration should this mod be started at?
Also, is this @.050 or advertised duration?
That question is hard to answer , because there is so many things that factor in , it would be best to go by the amount of idle vacuum , normal idle vacuum is around 17 to 18 inches. I would say some where around 14 inches or lower , usually a good sign is you loose control of your idle mixture screws.hope this helps.
I have a quickfuel brawler 650 double pumper.
the transferslots are adjusted but do I need to open the secondaries butterflies evenly open with the primaries butterflies or can I just adjust the idle speed with the secondaries?
My cruising AFR is about 14.5-15.5. But if I lean out my idle AFR my cruise AFR is to lean . What can I do about it? Thanks for the vids
It all comes down to how big a cam your running, if your cam is small you can usually get away with setting your transfer slots correctly and then adjusting your idle with your secondaries, but with a big cam you usually have to drill air bypass holes to lean your idle mixture and work with your idle air bleeds if needed.
For your second question when you lean your idle mixture with the idle fuel restrictors you also lean your transfer slots which will cause your cruise afr to go lean. So try leaning your idle with your idle air bleeds if they are changeable, 003 thousandths at a time, and put your idle fuel restictor back to stock and see how that works for you. Hope this helps.
@@holleycarbshowtosadvice40y90
Quickfuel brawler 650DP and 331 stroker 10.0-10.5 compression and cam 230/230 at 50 and 290/290. Dual plane intake. my ifr are still original at 32. Airbleeds also.
Prim jets 70 original and sec jets from 74 to 79.
Half THROTLLE fuel curve is flat at 12.3-12.7.
Full THROTLLE goes from rich 10.5 to 13.5.
My half throtlle is good but I need to adres the rich low rpm secondaries to high rpm lean
And my idle is 13.2 and will idle better at 13.7 but then cruise is to lean at 16. If I put cruise with idle screws to 15.4 then idle is rich at 13
You can't adjust the idle mixture screws for cruise that won't work, the idle mixture screws are for adjusting your idle afr, then when your at cruise your transfer slots ad fuel, then I tune with ifr and idle speed air bleed and float level adjustment for cruise their is a lot of variables but I start tuning from idle then cruise to mid throttle to wot. Hope this helps.
@@holleycarbshowtosadvice40y90
Do you mean I can lean out my idle with drilling the IAB bigger 0.003? Will this affect light cruise AFR?
Run manifold vacuum advance and you don’t need to drill holes!
High ignition timing does help but not a cure all, many times you have to bypass air at the throttle plate to get the mixture right.
Randy how can I get ahold of you
Thank you for watching