i'm going back oldschool th289 - blending in a lot of tech videos. hope ya'll enjoy. this is a channel for teaching and sharing knowledge - I miss doing stuff like this for you guys.
John, you’ll get it man. The truck in my profile pic was my dads also, and he couldn’t get it running. Do your research and keep faith. It’s been 7 years since my dad passed, and the truck is 100%. Best of luck man
Hi I am running 600cfm carb on a mild 351 clevo, has been hard to tune so I did what you said on you last video in regards to a fuel pump reg on a mechanical fuel pump an BAM! I works really well it was running nearly 8 psi on an old carb, the tune is more stable had to re adjust float heights it starts easier An tunes better so Thank you! Gene, Australia
Can you explain an Edelbrock carburetor? I have a 360FE and I have an off-idle stumble, I have tried all the different accelerator pump settings and changed the springs in the carburetor. I'm tuning with a wideband o2 gauge and the air/fuel mix is perfect at idle and cruise speed.
Remember that carbs and ignition are a balance. Where is your initial timing at? If you advance your initial mechanical to 10-18 (transfer slot vs idle rpm will determine what exact initial) and then put your vacuum advance on ported.
@@ThunderHead289 I'm using ported vacuum advance, also currently using the factory advance of 7 degrees of initial timing. I will try to set my initial mechanical advance to 10-18 and see what it does right now.
Would the addition of a Throttle Solenoid, to fix the air conditioner engine loading issue that many of us experience, cause mis-adjustment of the AP linkage as well?
I have an AMX with a crossram. I'm running 2 1850s and before jumping to Quickfuels I would like to see what I can do with the 1850s. Good learning. How about a lesson on two carb tuning.
I've been a chump these past couple months trying to figure out this off idle stumble, but after watching this video I went out and checked the lever and it had so much play you could almost put a pencil in it. Immediately closed the hood and took a walk to ponder my existence. When I finally came back, I adjusted the lever and the ole 460 runs like a champ now. Thanks Luke.
I learned a lot of this stuff from my dad a long time ago, and forgot most of it. He is gone now, and I have a carb engine to work on, so it is great having your channel to relearn from. It is great to know that old school mechanics all seem to have had the same real world applications! Thanks, and keep it up.!
I FINALLY broke down and bought my best first dedicated TH-cam recording piece - a Bluetooth mic. That plugs into a phone still 😂 Defiantly low tech! Thanks so much 👌
I got a stumble at low rpms when initially giving it gas other then that it blast thru but it also backfires on deceleration. U think the stumble/hesitation is because that accelerator screw needs tighting? And is the backfire because the idle mixture screws are too rich?
I’m sure you’ve fixed it by now, I’m curious if the park idle needs to be dropped, and accelerator pump clearance tightened. Let me know. I have same issue
Thanks just fixed my holly on a 67 mustang. Was stumbling off idle after vacuum tune. Didnt realize I needed to readjust the accel pump! Solid gold my man!
i think that might be the problem we're having with my daughter's 65 mustang. never knew that we were supposed to adjust the accelerator pump whenever we change the curb idle. gonna try that out tomorrow. glad to hear it fixed your problem.
No play at 0 throttle. .030 of clearance with throttle fully open. Which to achieve this, you have to be just barely BARELY on the accelerator pump with your idle throttle position. Does that make sense?
Your video was MUCH better than any Holley tech vids explaining how the pump is supposed to work, I “all of a sudden “ have a hesitation when I stab the throttle, even on the highway, if I backed off the throttle then back onto it, a split second hesitation, NEVER would I have considered the fact I lowered my idle and that directly affects the pump operation. THANK YOU👍
Same here! I guess it only affects it if you lower it, not raise your idle speed. Raise idle too much, you'll get over problems with the accelerater pump circuit. Gona varify mine tomorrow!
A "lean stumble" and a "bog" are two similar feeling situations caused by opposite actions. "Lean stumble" is just that ... LEAN. Too little fuel "Bogging" is too much fuel. RICH. Too much fuel Use the correct language.
Your explanation is close, but it's simpler than that. Liquid fuel has more inertia than air. So it takes longer for fuel changes to happen than air changes. The accelerator pump preempts the lag in fuel delivery.
It takes longer to draw the fuel than the air, so mechanically it is applied to bridge the gap. I’m not sure what I said that wasn’t correct, but I like the technicality of your explanation
@@ThunderHead289 I've thought about it too. But there's that, plus, a lot of people have different (even strange) ways of understanding (and misunderstanding!) a lot of these things and don't want to see a different point of view. I think all the time about building my own carburettor design in stages just to demonstrate how simple the concepts are. But I doubt I'll ever take the time. I really enjoy your videos, and I'm sure there are others who also don't complain so you never hear from them. When I understand something, I do enjoy relearning it. If there was one big book on carburettor theory that explained everything in detail, I'd read it over and over.
I looked everywhere for a mechanic that was comfortable working on my old carbureted car, and when he did, he ruined my engine timing, couldn't figure out the carb settings and I'm afraid to find out how he managed to disassemble and clean my spare carb without using any of the provided replacement gaskets.
I have had some stumbling problems before and did all the same ol fixes, plugs, wires, carburators, edelbrock, holley, demon, timing adjustments, fuel filters, fuel pumps, coils, distributor cap, roter, etc, still the same dead dog stumble from dead stop..... What could it be??? It's kinda rare and something you may never see or even guess that could shut down a high hp engine. Are you ready? AIR CLEANER....It has happened to me twice, a small air cleaner caused me to buy two new carburators, Holley 750, elderbrock 750. Finally exhausted one day and out of patience and money I inadvertantly closed the hood for another test drive. I had forgotten to put the air cleaner on as I was in a hurry and not just a little aggrivated. A 460 ford engine setting in a 1985 mustang should scream, and in this test drive it did. I couldn't believe such a simple thing a a undersized air cleaner could shut a engine down like that. One of the reasons I brought this up is I just built a 1971 plymouth Duster with a big block 400 with 10.5 to 1 pistons, 750 edelbrock and all the goodies. Changed the gear to 373 and ready for that test drive, flat on it's face, barley squeaked the 9'' wide tires. Oh what a disappointment. Had to be the carb, no the timing, what could it be? Then I remembered a long time aga a 460 ford engine. I ripped the small breather off and lined up on the road for what I belived would likely be another failure as this could never happen twice in a lifetime. It burnt the tires so bad that it climbed into third gear still smoking them dudes. Crazy right, Strange but true. Thanks for listening...
Hey, Luke. Hope you can answer a question. I have got a 77 f100 302 c6 Has GT 40p heads New lunati cam Edelbrock, torque 2 and a 600 quick fuel brawler. Truck runs great idol's perfect and sounds good. But as I keep tuning on this thing, I am stumped, cannot give the truck a quick throttle input, or it backfires through the carb You got any ideas
Would you have any insight or guidance for me? I have a 1974 ford with a 360 and manual trans. I swapped carbs to a Holley as the 1406 was needing a rebuild. I cannot get it to drive in gear, it will drive for a bit but dies and takes a while to restart. It will idle forever but fluctuates a little.
I got a built 355 sbc duel plain intake, headers, big cam, holly 600 cfm carburetor, its having a hard time accelerating and it makes a pop out of the carburetor somtimes if you really get on it quick but it runs great on the top end, it idles fine and revs up fine in neutral but sometimes itll do that pop even in neutral, i upgraded the acclerator pump nozzle from a 31 to a 35 and it seemed to help almost taking the stumble away but now its stalling when i roll around a turn or give it alot of gas and lay off it barely wants to run, any help would be appreciated, i think the nozzle needs to go even bigger or a jet might be plugged up, the idle is fluctuating now also, it will idle down low off the cam then the rpms will jump up to about 1500 rpms, then it drops back down to barely idling on a big cam
I have been chasing a stumble for about 2 weeks on this truck I put together. I have messed with the accelerator pump adjustment until I went insane, replaced the pump discharge nozzle to a larger size, timing, on and on and on. This was the fix. Thank you so much!!!
TH289, I have a stock 83 mustang Gt, the 4180c bowls are leaking and just WONT seal, so I bought a 4160. Long thing short Leaking down into cylinders. Okay I got screwed whatever. Switched to another 4160, this one worked amazing on a 454, it runs great, won’t start back and grunts like it’s high in time, but it runs smooth and good. Would it be a adjustment or a Fuel pressure issue? As it’s the second 4160 having similar issues. But not flooding cylinders(hydro lock). But the stock 4180c fires up every hit of key no grunts or anything. No gas nothing, just key and it starts. The 4180c was stock 7-9lbs of fuel pressure, the 4160 is a max of 7 lbs, should I Check and Lower fuel pressure or any ideas? I’ve been pulling hairs
My throttle linkage is functioning correctly, but I still have an off idle stumble. Even when I just try to bring up the idle slowly, around 1500 rpm the truck stumbles and BF. But if i pump it past 1500, the truck sounds good and I know the timing is good. Any ideas anyone?
Please help me. Im so so so confused. My Fiat 128 Rally 1300 1974 if not driving it idle okay till radiator fan goes on. No problem. Just when i drive and enjin begin get some heat it just cut of and dont want to start again. Have to wait to cool off. Then drive home and let it stand still and idle till radiator fan goes on. NO PROBS. Just when i drive so 1km it cut off again and have to wait car to cool down again. It give no probs if stand still and idle. Just when i drive and enjin is heat up. Will be realy happy if someone can help me please! Thanks so much.
my 4160 Cab on my 390 engine, i had to spray gas into the Carb for the car to start it wasn't spraying when you press gas, , i rebuilded the carb now it's spraying but now i have to press the gas to start the car once i stop pressing gas car turns off, any suggestions please?
How can i richen my low speed circuit. When i try to lug down my truck lets say down to 1000rpm it will start leaning out on my AFR gauge and stumble. I can recover the stumble with a light hit on the throttle. I suspect it is because the accelerator pump sends a shot of fuel in.
Help me before I burn this truck down lol I have to put the peddle to the floor to start it. It dose this before it gets going th-cam.com/video/CpI33Gw7D1M/w-d-xo.html BTW new motor and Summit carb Thanks for any suggestions
This video explains why having the pump misadjusted causes problems in both cases of it being too much or too little. Excellent info if you want to understand 'why' the adjustment is important.
You are super awesome guy you know what is going on with stuff like that. I hope and pray 🙏 that you and your family are doing well and safe from the coronavirus going around. I like your pooch..I have two they are in my profile picture. Ol bigfoot on the left side and Arnold on the right.. bigfoot is a pit bull mixed and 13 year's old and not doing good these days.arnold is a beagle and he is 9 years old and is doing pretty good right now he is my right hand man .lol. Be safe Luke.
I am aware of these adjustments however I'm having a problem with any carburetor I put on my firebird 421ci If I slightly open the throttle, it stumbles. I have tried setting the idle circuits lean and rich. It still happens. Intake leak maybe?
Sounds like it's more ignition timing related than anything. When testing with vacuum advance disconnected, id expect at least 12-18 initial, and 30-36 total, all in by 3500 at the latest
Hey Luke, got a question. I had a 1976 Dodge Aspen with the slant 6. From the time I bought it new, if I made to sharp of a right hand turn the car would stall. I took it to the dealership a number of times under warranty, but they never fixed it. After warranty a buddy with more mechanical knowledge than I changed carburetors. It helped, but still occasionally stalled. We moved from Illinois to south Florida and a friend with more mechanical knowledge adjusted the carb and I never had the issue again. Sorry I don't know the brand of carb it had, but have you ever come across this and what caused this issue? To you and yours, stay healthy and I enjoy your videos.👍
Dude I'm the person that brought the transfer slot thing to common knowledge. Before me and my original tech, it was seldom talked about. I'm thunderhead289 dude.
I have a motor craft 2bbl on a 360 I got the truck to learn carburetors and it has a rough idle and I set it to square like you always have talked about but idk what to do next I just need you to tune it haha
Great video Luke as always. It’s funny how the way different people absorb and interpret information, well differently, and I think that’s one reason I gravitated towards your vids, in that you generally deliver what I consider to be vital with instruction videos, and that is concept. The concept here is the dynamic relationship between off idle adjustment and the accelerator pump are joined at the hip with seemingly everything like AFR, initial mechanical advance, jet sizes, the throttle linkage, etc. it’s quite a bit but slowly I’m beginning to understand how necessary it is to comprehend the myriad of relationships between components, their adjustments, and not a single complements adjustment can stand alone. That would make one hell of a video, a video that explains the woven interconnected dynamic mess of displacement, bore, stroke, fuel delivery, variables in fuel delivery, eliminating variables in fuel delivery, timing, compression, valve events, engine under load, low load, heavy load, elevation, temperature, gearing, vehicle use, and the endless compromises one must understand in order to tune all of it to meet a very specific goal, which for everyone is different. Oh boy, there’s no end to the learning. Thanks for your sharing
Is it possible that cranking the curb idle screw down on a 2150 or 2100 allows the carburetor to drain into the engine after sitting for a couple of days?
Oh, it depends - that was a fun body style era if it was still the g body. An 88 was almost my first car, but I was afraid of it because I didn’t know how to work on anything.
@@ThunderHead289 Camaros are all F-bodies, the one you're thinking of is the 3rd gen, the one he is talking about is a 4th gen. I tend to prefer the 3rd gens because there is alot more room in the engine bay to work with, the 4th gen models can be a pain in the ass since a portion of the rear of the engine is under the cowl and there is in general just not as much room to work with. Still nice looking cars though, if your into mullets and Bon Jovi.
not correct ! you totally avoided the proper spring adjustment of the accel pump lever. you hold the carb wot and adujust spring nut until the lever starts to bottom out.....then screw in until you can wiggle the lever.
The pump lever would stick every time after adjustments over and over. It made the throttle too stiff, but I rigged a return spring for just the accelerator pump lever to stop that stumble. It ssems a bad design. No matter what pump or lever or adjustment, the thing will only return halfway, so next time you gst no fuel until it takes up the slack. Nobody talks about this but I saw it on every Hoĺley.
I have one for you Luke. I had an off idle stumble in my 72 Lemans. The car just has an Edelbrock carb and intake on it. The rest is stock. I did all the things you said here and scratched my head. Then I started over and checked the timing. I had it on manifold vacuum, so much for double checking, and was running 21 degrees at idle. LOL. I put it back to ported. I am back to 12 degrees mechanical at idle and 28 degrees maximum mechanical, with around 38 or 40 on vacuum. I reset the carb and it runs awesome. I wondered why it wasn't starting so easy. LOL Great video.
@@ThunderHead289 Thanks. It only has 88,000 miles on it right now. You saw it in Norwalk, Ohio when I worked with you on the 67 GTO. I grabbed my torque wrench out of it.. LOL
Not just Holley, Edlebrock too... Hey man thank you for pointing out the obvious, because t was not registering. I just finished a nightmare build that went from a Ford 400 to a 351M to an actual 302HO crank in a 351M block, by the casting codes, with 400 heads. Don't ask it's a long story. and on top of that, new cam, intake, card, valve springs, lifters, etc.and with all the changes getting the timing right was a battle and so I was thinking timing and hadn't even checked closely the accelerator pump. Sure enough it was loose as hell. tightened it up and what a difference... Thank you!
Thank you so much, and it's time to get a new carburetor for mine. Because I go to blast it to get out of that rough idol. And it still keeps idling very low...I have headers and all new fuel lines and wires. Only thing left is the Holly carb. And air intake.
You don't know my friend Dave. Back when I met him 15 years ago. Im telling you. He could set a Holly carb. And distributer. And it would fly.. If he could stand long enough. I would have him set my carb. But he is 73 years old. Has 2 different times. Broke his back. His stepson and I changed the gears in his 79 F150. 400 2barrle. Helped that 400 a little more peppy.275 replaced by 3 56.
I put a reman 600 Cfm holly 4 b on my old GMC snow truck at the end of summer, I didn't have time to play with it, I got it started, but at low idle, it ran ok after it got warm, I put fresh gas in no methonal, , And now its -7 outside, a blizzard, and it wont start, I have to pump the hell out of it to get it to even try to start, but it wont, I did have it started 3 days before and adjusted the curb idle down a bit, , So how do I get it to start in real cold weather?
Good video..I Love the vw I got one too .what have you done to it? What size motor is in it..I am having problems with my holley street wayyor carb on my 303 f150 I'm not getting any vacuum to it the edelbrock has it I don't know what to do it also has a edelbrock intake on it
Thunderhead...I have the AVS2 650 brand new. I've been having a stumble or bogging at take of or it seems like it's flooding can you give me pointer to adjust my f.a.r on a sb 350 with a rv cam. Thank you
Umm Im in Australia and I got a f100 truck and the pump gear on the carb is none existent and the rod that I think controls the secondary is also not there, but it still idles but backfires on acceleration and runs rich. Could this be Becuase the motor was predominantly set up for LPG?
Depends on the carb - they are both main jets as a v8 intake is basically split to two 4 bangers by the intake. Something like a weber 32/36 had a primary and secondary jet, progressive bores into common manifold
Actually,, you forgot to mention the transition slots which are the accelerator pump, so to speak, which allows fuel to reach the manifold before the acc. Pump shot, because they are at the bottom of the carb. Which is closer to the manifold.
Good explanation. My Holley book for a street dominator I had years ago said I should have a little gap (I think .015") between the accelerator pump arm and the throttle linkage. From what I've read, you may want a split second of air before spraying fuel into the boosters. I feel like this will vary between engine combo's so maybe no gap or maybe a little gap.
Hi im Bob i really some advice im stumped. Been around this stuff for years so im not new to it. I have a Rochester 2bb carb on a 305 new rebuild it starts nice runs nice. But with choke fully open at idle it wont sit on cam to idle properly little on high side. But if i goose the throttle it idles down and sits on cam. then if i give it gas again does the same thing return springs are strong. Its like engine vacuum holds open a bit.,. Again if i goose throttle she idles down like it should. If i turn off car its fine drops down on cam.. Im stupped here any suggestions? Thanks i would appreiate it.
I really enjoy your videos. Catching up as I put the finishing touches on my 63 Merc Comet S-22 engine bay. Your carb and engine/distributor videos have been very helpful.
Great videos Luke keep em coming I have a boat 351 Windsor 650 Holley marine all insides r new got it set too ur videos of course but they is a spot here we go at the lake that I have too idle in (no wake) which is a long way into the spot it will stall out sometimes it starts right back up n sometimes it takes a few times too get it too start back any advice would b greatly appreciated...... Joshua
Wouldn't the number 2 hole be best on the primary side for a foot brake racer that has to come up on the converter to 2000 rpm so your not already using like 20% of the pump cam?
Thanks, I have a boat with more engine than the drive should be pushing. I never paid much attention to my accelerator pumps cause I always take off easy. I'll still set things correctly though so it all works together properly. I bet there's a little gap in the linkage setup.
can you just show or show and tell me what you're talking about should look like? It seemed you went over two or three times what it shouldn't do or what you shouldn't see...
Could never get a Edelbrock carb tuned right. Tried everything to get rid of my off idle bog. Bought a summit carb and the rest is history. Holleys are so much better but you need more carb knowledge to adjust a Holley. Thanks for the video.
This helped a lot. So I made adjustments so there is no play between the accelerator pump arm and pump diaphragm lever. But this adjustment made the idle way too fast. So should I move the screw on the throttle to the 1st position to obtain a slower idle?
Man, I got behind in your videos, so I've got 6 more to watch. Which means I get to binge! Anyway, thanks, Luke, for the great tutorials. You're my favorite teacher by far.
i'm going back oldschool th289 - blending in a lot of tech videos. hope ya'll enjoy.
this is a channel for teaching and sharing knowledge - I miss doing stuff like this for you guys.
Ty much man. I have learned so much from yourself and junkyard digs/ Dylan mc cool. Glad yall can still make videos. Be safe.
Thanks man! Always look forward to your videos, and can't wait to get to tune the carb on my SBF with your guidance.
Would like to see some motor craft 2150 vids if possible.
@@b_reed1717 second that request - i have one on my '68 289 and can use a vid on it.
Have you ever used a thompson performance power blast plate on a holley? Do they really make any diffrence?
Thank you for this my dad passed away and I'm trying my best to get his car running
Man, that hits me in the soul. Are you around Iowa? I’d help you
John, you’ll get it man. The truck in my profile pic was my dads also, and he couldn’t get it running. Do your research and keep faith. It’s been 7 years since my dad passed, and the truck is 100%. Best of luck man
Sounds rough man good luck
❤
Feel you there. My pops is still with me but can't really do much anymore. When you master it pass it along to your children like our dad's have!
Hi I am running 600cfm carb on a mild 351 clevo, has been hard to tune so I did what you said on you last video in regards to a fuel pump reg on a mechanical fuel pump an BAM! I works really well it was running nearly 8 psi on an old carb, the tune is more stable had to re adjust float heights it starts easier An tunes better so Thank you! Gene, Australia
Can you explain an Edelbrock carburetor? I have a 360FE and I have an off-idle stumble, I have tried all the different accelerator pump settings and changed the springs in the carburetor. I'm tuning with a wideband o2 gauge and the air/fuel mix is perfect at idle and cruise speed.
Remember that carbs and ignition are a balance. Where is your initial timing at?
If you advance your initial mechanical to 10-18 (transfer slot vs idle rpm will determine what exact initial) and then put your vacuum advance on ported.
@@ThunderHead289 I'm using ported vacuum advance, also currently using the factory advance of 7 degrees of initial timing. I will try to set my initial mechanical advance to 10-18 and see what it does right now.
I have 360 in my 74 f100. I run 20 degrees initial, 36 total and ported vacuum of 10. Helps with the low compression blues
Would the addition of a Throttle Solenoid, to fix the air conditioner engine loading issue that many of us experience, cause mis-adjustment of the AP linkage as well?
I have an AMX with a crossram. I'm running 2 1850s and before jumping to Quickfuels I would like to see what I can do with the 1850s. Good learning. How about a lesson on two carb tuning.
So what was the 2 second trick? I also did not see you show the accelerator pump cam on the carburetor.
For one, the title says "2 second fix" not trick, for two .... are you blind?
hi
I've been a chump these past couple months trying to figure out this off idle stumble, but after watching this video I went out and checked the lever and it had so much play you could almost put a pencil in it. Immediately closed the hood and took a walk to ponder my existence. When I finally came back, I adjusted the lever and the ole 460 runs like a champ now. Thanks Luke.
I learned a lot of this stuff from my dad a long time ago, and forgot most of it. He is gone now, and I have a carb engine to work on, so it is great having your channel to relearn from. It is great to know that old school mechanics all seem to have had the same real world applications! Thanks, and keep it up.!
Great as always Luke, best part? The mic level is perfect volume and clear, love it! Don't want to miss a word of this gold!
I FINALLY broke down and bought my best first dedicated TH-cam recording piece - a Bluetooth mic.
That plugs into a phone still 😂
Defiantly low tech!
Thanks so much 👌
I got a stumble at low rpms when initially giving it gas other then that it blast thru but it also backfires on deceleration. U think the stumble/hesitation is because that accelerator screw needs tighting? And is the backfire because the idle mixture screws are too rich?
Installed a 600cfm 4 barrel holly carb on my 81 Ford f100 302, seems like it idles a little high and when put in any gear it dies.
I’m sure you’ve fixed it by now, I’m curious if the park idle needs to be dropped, and accelerator pump clearance tightened. Let me know. I have same issue
Thanks just fixed my holly on a 67 mustang. Was stumbling off idle after vacuum tune. Didnt realize I needed to readjust the accel pump! Solid gold my man!
i think that might be the problem we're having with my daughter's 65 mustang. never knew that we were supposed to adjust the accelerator pump whenever we change the curb idle. gonna try that out tomorrow.
glad to hear it fixed your problem.
@@thomasdeaton8768 same here! Gona check tomorrow! If not, I'm gona get little bigger nozzles for the primary.
Great video! the only way people will stop being afraid of carburetors is by learning about them. Can’t wait for the edelbrock video!
I've watched the video a few times, but I'm still confused. Do I want the slack in between the throttle and acc pump linkage or not. Thanks!
No play at 0 throttle. .030 of clearance with throttle fully open.
Which to achieve this, you have to be just barely BARELY on the accelerator pump with your idle throttle position.
Does that make sense?
I think I owe you a nickel! 1961 mercury comet with a 302
I just bought a 77 F150 with a 351M... Ran like crap. After viewing numerous vids, I have it dialed in perfectly. Thanks Luke!
Neve knew the idle adjustment altered the accelerator pump setting, cool
Your video was MUCH better than any Holley tech vids explaining how the pump is supposed to work, I “all of a sudden “ have a hesitation when I stab the throttle, even on the highway, if I backed off the throttle then back onto it, a split second hesitation, NEVER would I have considered the fact I lowered my idle and that directly affects the pump operation. THANK YOU👍
Same here! I guess it only affects it if you lower it, not raise your idle speed. Raise idle too much, you'll get over problems with the accelerater pump circuit.
Gona varify mine tomorrow!
A "lean stumble" and a "bog" are two similar feeling situations caused by opposite actions.
"Lean stumble" is just that ... LEAN. Too little fuel
"Bogging" is too much fuel. RICH. Too much fuel
Use the correct language.
Man I wish you could tune my 73 Chevy stepside
Your explanation is close, but it's simpler than that. Liquid fuel has more inertia than air. So it takes longer for fuel changes to happen than air changes. The accelerator pump preempts the lag in fuel delivery.
It takes longer to draw the fuel than the air, so mechanically it is applied to bridge the gap. I’m not sure what I said that wasn’t correct, but I like the technicality of your explanation
@@ThunderHead289 I don't necessarily think what you said was incorrect, just maybe a little off-target, or at least I might hear it that way.
You don’t know how bad I actually want to explain all this in an in depth way. Folks eyes just glaze over unfortunately
@@ThunderHead289 I've thought about it too. But there's that, plus, a lot of people have different (even strange) ways of understanding (and misunderstanding!) a lot of these things and don't want to see a different point of view.
I think all the time about building my own carburettor design in stages just to demonstrate how simple the concepts are. But I doubt I'll ever take the time.
I really enjoy your videos, and I'm sure there are others who also don't complain so you never hear from them. When I understand something, I do enjoy relearning it. If there was one big book on carburettor theory that explained everything in detail, I'd read it over and over.
THANK YOU!!!!! 87 El Camino has been killing me. Exactly what I needed
Learned a ton from your channel!
This is sadly a lost art. Most mechanics I know lift their eyebrows when you even say the word carb....
I looked everywhere for a mechanic that was comfortable working on my old carbureted car, and when he did, he ruined my engine timing, couldn't figure out the carb settings and I'm afraid to find out how he managed to disassemble and clean my spare carb without using any of the provided replacement gaskets.
I have had some stumbling problems before and did all the same ol fixes, plugs, wires, carburators, edelbrock, holley, demon, timing adjustments, fuel filters, fuel pumps, coils, distributor cap, roter, etc, still the same dead dog stumble from dead stop..... What could it be??? It's kinda rare and something you may never see or even guess that could shut down a high hp engine. Are you ready? AIR CLEANER....It has happened to me twice, a small air cleaner caused me to buy two new carburators, Holley 750, elderbrock 750. Finally exhausted one day and out of patience and money I inadvertantly closed the hood for another test drive. I had forgotten to put the air cleaner on as I was in a hurry and not just a little aggrivated. A 460 ford engine setting in a 1985 mustang should scream, and in this test drive it did. I couldn't believe such a simple thing a a undersized air cleaner could shut a engine down like that. One of the reasons I brought this up is I just built a 1971 plymouth Duster with a big block 400 with 10.5 to 1 pistons, 750 edelbrock and all the goodies. Changed the gear to 373 and ready for that test drive, flat on it's face, barley squeaked the 9'' wide tires. Oh what a disappointment. Had to be the carb, no the timing, what could it be? Then I remembered a long time aga a 460 ford engine. I ripped the small breather off and lined up on the road for what I belived would likely be another failure as this could never happen twice in a lifetime. It burnt the tires so bad that it climbed into third gear still smoking them dudes. Crazy right, Strange but true. Thanks for listening...
Hey, Luke. Hope you can answer a question. I have got a 77 f100 302 c6 Has GT 40p heads New lunati cam Edelbrock, torque 2 and a 600 quick fuel brawler. Truck runs great idol's perfect and sounds good. But as I keep tuning on this thing, I am stumped, cannot give the truck a quick throttle input, or it backfires through the carb You got any ideas
I'm seeing relatively recent replies here. I'm going to look but do you have a video on the Edelbrock? I have that carb and the off idle lean stumble.
Would you have any insight or guidance for me? I have a 1974 ford with a 360 and manual trans. I swapped carbs to a Holley as the 1406 was needing a rebuild. I cannot get it to drive in gear, it will drive for a bit but dies and takes a while to restart. It will idle forever but fluctuates a little.
This video is way better then the one from Holley thanks man
I got a built 355 sbc duel plain intake, headers, big cam, holly 600 cfm carburetor, its having a hard time accelerating and it makes a pop out of the carburetor somtimes if you really get on it quick but it runs great on the top end, it idles fine and revs up fine in neutral but sometimes itll do that pop even in neutral, i upgraded the acclerator pump nozzle from a 31 to a 35 and it seemed to help almost taking the stumble away but now its stalling when i roll around a turn or give it alot of gas and lay off it barely wants to run, any help would be appreciated, i think the nozzle needs to go even bigger or a jet might be plugged up, the idle is fluctuating now also, it will idle down low off the cam then the rpms will jump up to about 1500 rpms, then it drops back down to barely idling on a big cam
I have been chasing a stumble for about 2 weeks on this truck I put together. I have messed with the accelerator pump adjustment until I went insane, replaced the pump discharge nozzle to a larger size, timing, on and on and on. This was the fix. Thank you so much!!!
TH289, I have a stock 83 mustang Gt, the 4180c bowls are leaking and just WONT seal, so I bought a 4160. Long thing short Leaking down into cylinders. Okay I got screwed whatever. Switched to another 4160, this one worked amazing on a 454, it runs great, won’t start back and grunts like it’s high in time, but it runs smooth and good. Would it be a adjustment or a Fuel pressure issue? As it’s the second 4160 having similar issues. But not flooding cylinders(hydro lock). But the stock 4180c fires up every hit of key no grunts or anything. No gas nothing, just key and it starts. The 4180c was stock 7-9lbs of fuel pressure, the 4160 is a max of 7 lbs, should I Check and Lower fuel pressure or any ideas? I’ve been pulling hairs
My throttle linkage is functioning correctly, but I still have an off idle stumble. Even when I just try to bring up the idle slowly, around 1500 rpm the truck stumbles and BF. But if i pump it past 1500, the truck sounds good and I know the timing is good. Any ideas anyone?
Please help me. Im so so so confused.
My Fiat 128 Rally 1300 1974 if not driving it idle okay till radiator fan goes on. No problem.
Just when i drive and enjin begin get some heat it just cut of and dont want to start again. Have to wait to cool off. Then drive home and let it stand still and idle till radiator fan goes on. NO PROBS. Just when i drive so 1km it cut off again and have to wait car to cool down again.
It give no probs if stand still and idle. Just when i drive and enjin is heat up.
Will be realy happy if someone can help me please!
Thanks so much.
my 4160 Cab on my 390 engine, i had to spray gas into the Carb for the car to start it wasn't spraying when you press gas, , i rebuilded the carb now it's spraying but now i have to press the gas to start the car once i stop pressing gas car turns off, any suggestions please?
How can i richen my low speed circuit. When i try to lug down my truck lets say down to 1000rpm it will start leaning out on my AFR gauge and stumble. I can recover the stumble with a light hit on the throttle. I suspect it is because the accelerator pump sends a shot of fuel in.
I am fowling plugs and can’t seem to get my brawler 750 for the street I have a 383 elder Brock signature series motor
Help me before I burn this truck down lol I have to put the peddle to the floor to start it. It dose this before it gets going th-cam.com/video/CpI33Gw7D1M/w-d-xo.html BTW new motor and Summit carb Thanks for any suggestions
The mic volume was queit, but perfect for me! I didn't have to turn the volume up all the way either. Thanks for the ThunderHead Tech Tip.. Lol. 👍
This video explains why having the pump misadjusted causes problems in both cases of it being too much or too little. Excellent info if you want to understand 'why' the adjustment is important.
You are super awesome guy you know what is going on with stuff like that. I hope and pray 🙏 that you and your family are doing well and safe from the coronavirus going around. I like your pooch..I have two they are in my profile picture. Ol bigfoot on the left side and Arnold on the right.. bigfoot is a pit bull mixed and 13 year's old and not doing good these days.arnold is a beagle and he is 9 years old and is doing pretty good right now he is my right hand man .lol. Be safe Luke.
I can't wait to see the Edelbrock . Because I having problem with it . And how you explained things I might have a chance to fix it 😁
Well I owe you 2 nickels , thx for tip.. carbs works so much better.
Another great video, information that Holley should supply with there carbs when you buy them.
Verry helpful! especially given i just got done rebuilding my Holley off my '74 F350
I am aware of these adjustments however I'm having a problem with any carburetor I put on my firebird 421ci
If I slightly open the throttle, it stumbles. I have tried setting the idle circuits lean and rich. It still happens.
Intake leak maybe?
Sounds like it's more ignition timing related than anything.
When testing with vacuum advance disconnected, id expect at least 12-18 initial, and 30-36 total, all in by 3500 at the latest
I'm sure somebody learn from this and maybe is hanging out in the garage
mine bogs off idle and the springs compresses some then catches up....killin me
Hey Luke, got a question. I had a 1976 Dodge Aspen with the slant 6. From the time I bought it new, if I made to sharp of a right hand turn the car would stall. I took it to the dealership a number of times under warranty, but they never fixed it. After warranty a buddy with more mechanical knowledge than I changed carburetors. It helped, but still occasionally stalled. We moved from Illinois to south Florida and a friend with more mechanical knowledge adjusted the carb and I never had the issue again. Sorry I don't know the brand of carb it had, but have you ever come across this and what caused this issue? To you and yours, stay healthy and I enjoy your videos.👍
Bob Walker Most likely the original carb. was a Holley. Hated those 1 bbl. stalling in turns, flooding on hot start. The 2 bbl was likely a carter.
You adjust the fast idle and never mentioned how YOU FUCKED UP THE TRANSFER SLOT!!!@!!
Dude I'm the person that brought the transfer slot thing to common knowledge. Before me and my original tech, it was seldom talked about.
I'm thunderhead289 dude.
Always love to learn from a guy with a bottle opener ring :) Great video
I have a motor craft 2bbl on a 360 I got the truck to learn carburetors and it has a rough idle and I set it to square like you always have talked about but idk what to do next I just need you to tune it haha
What is your initial ignition timing?
@@ThunderHead289 I havent had the time to do timing yet and I still need to get a vacuum gauge
@thunderhead289 where is the best place to put the vacuum gauge on the 2 bbl
Very informative video, thank you sir
Great video Luke as always. It’s funny how the way different people absorb and interpret information, well differently, and I think that’s one reason I gravitated towards your vids, in that you generally deliver what I consider to be vital with instruction videos, and that is concept. The concept here is the dynamic relationship between off idle adjustment and the accelerator pump are joined at the hip with seemingly everything like AFR, initial mechanical advance, jet sizes, the throttle linkage, etc. it’s quite a bit but slowly I’m beginning to understand how necessary it is to comprehend the myriad of relationships between components, their adjustments, and not a single complements adjustment can stand alone. That would make one hell of a video, a video that explains the woven interconnected dynamic mess of displacement, bore, stroke, fuel delivery, variables in fuel delivery, eliminating variables in fuel delivery, timing, compression, valve events, engine under load, low load, heavy load, elevation, temperature, gearing, vehicle use, and the endless compromises one must understand in order to tune all of it to meet a very specific goal, which for everyone is different. Oh boy, there’s no end to the learning. Thanks for your sharing
Always look forward to your tech videos. Thanks for great information. You have really helped me out. Not afraid to tackle my carb now.
Releases subscription to the channel, big fan
Great video brother very informative
Is it possible that cranking the curb idle screw down on a 2150 or 2100 allows the carburetor to drain into the engine after sitting for a couple of days?
Nay, not at all related
HOLLY CARBS HELL YES
(Edit): what do you think about the 1993 chevy camaro. thoughts?
Oh, it depends - that was a fun body style era if it was still the g body.
An 88 was almost my first car, but I was afraid of it because I didn’t know how to work on anything.
@@ThunderHead289 Camaros are all F-bodies, the one you're thinking of is the 3rd gen, the one he is talking about is a 4th gen. I tend to prefer the 3rd gens because there is alot more room in the engine bay to work with, the 4th gen models can be a pain in the ass since a portion of the rear of the engine is under the cowl and there is in general just not as much room to work with. Still nice looking cars though, if your into mullets and Bon Jovi.
Do you ever work on 2 barrel ford carberators?
Legit didn’t even think of the accelerator pump adjustment after changing idle speed
Give it a shot tommorow reckon it’ll be perfect
not correct ! you totally avoided the proper spring adjustment of the accel pump lever. you hold the carb wot and adujust spring nut until the lever starts to bottom out.....then screw in until you can wiggle the lever.
That might be the most silly way I have ever heard of adjusting it honestly
@@ThunderHead289 that is per Holley.....you do nothing in YOUR video to check for bottoming out the pump gasket.
The pump lever would stick every time after adjustments over and over. It made the throttle too stiff, but I rigged a return spring for just the accelerator pump lever to stop that stumble. It ssems a bad design. No matter what pump or lever or adjustment, the thing will only return halfway, so next time you gst no fuel until it takes up the slack. Nobody talks about this but I saw it on every Hoĺley.
I have one for you Luke. I had an off idle stumble in my 72 Lemans. The car just has an Edelbrock carb and intake on it. The rest is stock. I did all the things you said here and scratched my head. Then I started over and checked the timing.
I had it on manifold vacuum, so much for double checking, and was running 21 degrees at idle. LOL. I put it back to ported. I am back to 12 degrees mechanical at idle and 28 degrees maximum mechanical, with around 38 or 40 on vacuum. I reset the carb and it runs awesome. I wondered why it wasn't starting so easy. LOL Great video.
Man, I am so pumped that it worked out for you and you can now enjoy your ride 💪
That’s the only reason I do this TH-cam thing
@@ThunderHead289 Thanks. It only has 88,000 miles on it right now. You saw it in Norwalk, Ohio when I worked with you on the 67 GTO. I grabbed my torque wrench out of it.. LOL
Not just Holley, Edlebrock too... Hey man thank you for pointing out the obvious, because t was not registering. I just finished a nightmare build that went from a Ford 400 to a 351M to an actual 302HO crank in a 351M block, by the casting codes, with 400 heads. Don't ask it's a long story. and on top of that, new cam, intake, card, valve springs, lifters, etc.and with all the changes getting the timing right was a battle and so I was thinking timing and hadn't even checked closely the accelerator pump. Sure enough it was loose as hell. tightened it up and what a difference... Thank you!
Thanks, Luke.
Good, precise information explained so that even I "a self-proclaimed non carb guy" can understand.
Good stuff !!
Thank you so much, and it's time to get a new carburetor for mine. Because I go to blast it to get out of that rough idol. And it still keeps idling very low...I have headers and all new fuel lines and wires. Only thing left is the Holly carb. And air intake.
You don't know my friend Dave. Back when I met him 15 years ago. Im telling you. He could set a Holly carb. And distributer. And it would fly.. If he could stand long enough. I would have him set my carb. But he is 73 years old. Has 2 different times. Broke his back. His stepson and I changed the gears in his 79 F150. 400 2barrle. Helped that 400 a little more peppy.275 replaced by 3 56.
I put a reman 600 Cfm holly 4 b on my old GMC snow truck at the end of summer, I didn't have time to play with it, I got it started, but at low idle, it ran ok after it got warm, I put fresh gas in no methonal, , And now its -7 outside, a blizzard, and it wont start, I have to pump the hell out of it to get it to even try to start, but it wont, I did have it started 3 days before and adjusted the curb idle down a bit, , So how do I get it to start in real cold weather?
Good video..I Love the vw I got one too .what have you done to it? What size motor is in it..I am having problems with my holley street wayyor carb on my 303 f150 I'm not getting any vacuum to it the edelbrock has it I don't know what to do it also has a edelbrock intake on it
Thunderhead...I have the AVS2 650 brand new. I've been having a stumble or bogging at take of or it seems like it's flooding can you give me pointer to adjust my f.a.r on a sb 350 with a rv cam. Thank you
Umm Im in Australia and I got a f100 truck and the pump gear on the carb is none existent and the rod that I think controls the secondary is also not there, but it still idles but backfires on acceleration and runs rich. Could this be Becuase the motor was predominantly set up for LPG?
Are both jets supposed to work at the same time? For a 2 bbl? Or is one a idle jet and the other a main jet.
Depends on the carb - they are both main jets as a v8 intake is basically split to two 4 bangers by the intake.
Something like a weber 32/36 had a primary and secondary jet, progressive bores into common manifold
@ThunderHead289 I know it's a stupid question lol. So my holley twenty two forty five should have two squirts every time I press on the accelerator?
Actually,, you forgot to mention the transition slots which are the accelerator pump, so to speak, which allows fuel to reach the manifold before the acc. Pump shot, because they are at the bottom of the carb. Which is closer to the manifold.
Hello bro. Kindly tell about 1982 toyota corolla dx distributor vacuum hoses connection to carburator hoses.Thanx
Just like in Vespa Lx 125 with Walbro carb, fantastic, thank you!
Good explanation. My Holley book for a street dominator I had years ago said I should have a little gap (I think .015") between the accelerator pump arm and the throttle linkage. From what I've read, you may want a split second of air before spraying fuel into the boosters. I feel like this will vary between engine combo's so maybe no gap or maybe a little gap.
Hi im Bob i really some advice im stumped. Been around this stuff for years so im not new to it. I have a Rochester 2bb carb on a 305 new rebuild it starts nice runs nice. But with choke fully open at idle it wont sit on cam to idle properly little on high side. But if i goose the throttle it idles down and sits on cam. then if i give it gas again does the same thing return springs are strong. Its like engine vacuum holds open a bit.,. Again if i goose throttle she idles down like it should. If i turn off car its fine drops down on cam.. Im stupped here any suggestions? Thanks i would appreiate it.
I really enjoy your videos. Catching up as I put the finishing touches on my 63 Merc Comet S-22 engine bay. Your carb and engine/distributor videos have been very helpful.
I like to use a feeler gauge of 0.015 for the gap setting on a Holley. I think Holley video says that. Check their video though for sure. Thanks
Do you work in a speed shop or something? I'm wondering where you are seeing all these misadjusted Holley carbs.
Great videos Luke keep em coming I have a boat 351 Windsor 650 Holley marine all insides r new got it set too ur videos of course but they is a spot here we go at the lake that I have too idle in (no wake) which is a long way into the spot it will stall out sometimes it starts right back up n sometimes it takes a few times too get it too start back any advice would b greatly appreciated......
Joshua
Wouldn't the number 2 hole be best on the primary side for a foot brake racer that has to come up on the converter to 2000 rpm so your not already using like 20% of the pump cam?
Thanks, I have a boat with more engine than the drive should be pushing. I never paid much attention to my accelerator pumps cause I always take off easy. I'll still set things correctly though so it all works together properly. I bet there's a little gap in the linkage setup.
can you just show or show and tell me what you're talking about should look like? It seemed you went over two or three times what it shouldn't do or what you shouldn't see...
Thank you so very much for a concise easy to understand tutorial- much appreciated.
Could never get a Edelbrock carb tuned right. Tried everything to get rid of my off idle bog. Bought a summit carb and the rest is history. Holleys are so much better but you need more carb knowledge to adjust a Holley. Thanks for the video.
This helped a lot. So I made adjustments so there is no play between the accelerator pump arm and pump diaphragm lever. But this adjustment made the idle way too fast. So should I move the screw on the throttle to the 1st position to obtain a slower idle?
I need help with my 62 merc Meteor. She STILL overheats. Mn lives matter
You should show and not just tell what you did to accelerator screw. That does not make any sence
THANK YOU!! Very helpful man you’re the man!
Such a smart bloke love this guy
Thanks for the information TH289! Where r u located at ?
Good video as always.
Is that ring a bottle opener?
It is indeed - I’m kind of a rough around the edges guy 😅
@@ThunderHead289 Pretty cool. Lol
Thanks Luke, Please make a video on the Edelbrock.Your tutorials are most helpful.
This video helped fix my problem, thanks!
I know you dont like edelbrock but you should make a few vids on them
Man, I got behind in your videos, so I've got 6 more to watch. Which means I get to binge! Anyway, thanks, Luke, for the great tutorials. You're my favorite teacher by far.
great tip,something I knew , but many people dont.