I would say the flow number would end up in the 270 to 280 cfm range as long as supporting chamber mods are done. Those chambers are very tight on the 1.89s and shroud the valves pretty heavily. I have a set of 706s I just finished porting and will have them flow bench soon.
This is some good stuff here! Love finding guys willing to share knowledge on this stuff thank you 👍 I’m currently building a 4.8 for my s10 blazer project!
If you can upgrade/use Gen 4 pistons and rods, this is the only thing I wish I had done different on my own 4.8 Turbo build. But if your building a moderate NA build under 7500 rpm you’ll most likely be fine with a Gen 3 setup. Thanks for watching and the feedback I appreciate it!!! JD
Area of a circle and diameter of a cirlce are two very different things. 1.89" valve = 2.80insq of area 2" valve = 3.14 insq 2.165 valve = 3.68 insq 2.2 valve = 3.8insq
True, I’m referring to the width or diameter of a circle. There are applications for the area of a port if you were mapping out a new port or similar. Thanks for sharing the area of various valve sizes! JD
Full of great information, but if I may say so without hurting your feelings, I felt like I was listening to my 10th grade chemistry teacher. Not the end of the world, I had some good times in that class in between droning lectures, haha.
Another great vid, and I love to talk porting theory myself. I have done some of the same research, but on a 2.02 valve. The theoretical formula that I have used is one that I found on the web a few years back when researching the same thing that you are in the pursuit of researching. Throat area x115. In this case that formula would have this head at 266.8cfm max with a 1.7199 (91%) throat. Your work looks beautiful as usual and I'm interested to see what that small valve does on the bench with that nice port behind it.
I like the formula you shared! 266.x cfm is fairly close to my guess, in a way. 306cfm x .945= 289.17 x .9244= 267.30cfm I’ll definitely keep your formula handy! Thanks for watching and the feedback I appreciate it! JD
Here’s an interesting comparison, using the theoretical formula of flow based on the area of the bowl. My 225cc ports use a 1.800” bowl w/2.00” valve: Area 2.5434 x 115= 292.49 cfm Area= 3.14 x r x r r= Bowl size/2 My 1.800” bowl flowed 306+ cfm which shows you can exceed the formula. To find the actual multiplier: 306/2.5534= 120.311 2.5434 x 120.311= 305.99 cfm This new formula is very interesting! JD
@@HeadFlowInc Hey that's interesting. The formula that I shared has that at 292.6. Ill experiment with yours on the next set of heads that I flow. Good stuff!
Mr. Headflow, a little more info on my build in my earlier email. The engine will utilize ported 862 heads (as you have described in this and other videos with 2.0 and 1.875 exhausts valves. Thanks again.
No problem, just take the head gasket you plan to use on the 5.3 and use it to scribe or mark the bore opening because you’ll hurt flow if the chamber is covered by the gasket. JD
@@HeadFlowInc JD: Thanks for the response. Actually, I prefer to scribe the cylinder head with the final bore on the block so as to not create a step between the cylinder head and the cylinder wall esp since there can be quite a difference between the cylinder bore and the gasket bore. Just saying. Keep up the good work!
Good idea! Attention to the details will pay off. We try to run head gaskets as close to bore size as possible. Your method is good because a lot of people run gasket bore way too big. JD
Excellent stuff Jeff. Thanks for sharing. I'm very interested to see the results. I've been working on a set of 706's for an LQ4 and I want Manley ProFlo 2" intake valves but I'm trying to figure the gains vs cost. Gotta get the bowls cut anyway so, might was well step it up to the 2" intake valves! Very interesting.
Ultimately the 2.00” valve can flow more if the combo can use it. A max ported 1.89”/1.95” head would be a great street/strip 4.8/5.3 build, especially up to 550-575hp NA. Or a great torque head for a larger CID. JD
@@chriswise1232 Not trying to take anything away from JD here but, the most cost effective valve to use are the ones that came in your heads if they're reusable. Look for wear on the stem in the guide area. See something you dont like, get factory replacements. Rust on the seat area is a no go for me. Or, any rust for that matter. Those make for smoke in the long run. I'll use those for a cut-down I'll use for bowl cut templates. I may re-use a valve that has a stain from parts washing but, the stain goes away for me after valve lapping. If not, bottom drawer of the toolbox she goes. Back-flowing the valves makes a difference for a couple extra cfm worth of flow but, if you're running the factory size the added labor negates the gain. The quality of your valve job itself (multi-angle valve seats), your machinist's quality of work and your bowl blending are the two most important areas to look at if your hand porting your own heads. For me, the bowl cut percentages you select and quality of your machinist's work come next along with port blending, consistency and repeatedness. In a shorter response, the best economy valve for keeping the factory sized valve, is the factory valve. What makes the difference, as with any other is the quality of what you can throw at it. I leave them factory and give all I know or if I go to a bigger size, I get the best I can afford. I'm a huge fan of Manley ProFlo
Look at Summit Racing for cylinder head configurations, and the All on Cylinders Ultimate LS Guide. I'd love higher port volume and valve size without screwing with the 61 cc chamber. Remember Beneroulli's principle of venturi effect. If I could get Rectangular port Heads with 61cc chamber with bigger valves I would get them.
Terry Wilkes has some heads on eBay. The 862’s are 227cc intakes rated at 308 @.600. And the 243s are 228cc and a little more cfm. Have you ever maxed out some 862’s ? I couldn’t imagine the gm castings are so much different you cannot do a 243 stage 20 on a 862 cast. But you tell me idk chit but what you or others have said
My 225cc intake ports flow 306+ cfm @.600 and outflow a stock 243/799 at all lift points. This is with a 2.00” valve and a factory valve job zero back cuts on the valves. Yes all the cathedral port heads can be ported to flow the same. JD
Mr. HeadFlow, I very much appreciate all your videos (long time subscriber). Kinda new to the LS scene. Am building a 5.3 with 7.820ish bore and 4 inch stroke for a street S10 manual. Would very much appreciate your insight and recommendation on cam sprecs for said engine. Thanks for your time and expertise.
I really like the new Summit 8720 cam, it equals the Sloppy Stage 2 cam at Peak but makes way more Torque throughout the useable rpm range. .600/.600 @.050 218/227 adv 278/287 LSA 112
Porting a set of 862 heads for my 370ci LQ4, I was shooting for 460whp or better and was wondering if you could give me any tips. I’ve been watching your videos a lot and have found them very helpful by the way👍🏼
I’m thinking you are definitely going to need a 2.00”-2.02” intake valve, competition valve job and unshrouding both the intake/exhaust valves in the chamber. 88-90% bowl cut/blend Swirl ramp removal Valve guide boss reduction Remove the rocker bolt lump. To get 460 whp NA you’re going to need 550-60+ HP crankshaft. The crankshaft power depends of what type transmission you’ll use. 300+ cfm heads will definitely help! We’ve found there’s even some issues with shrouding the stock exhaust valve on the 862’s because the chamber is so small it barely allows the exhaust valve to open. JD
@@HeadFlowInc Thanks for the info👍🏼 I took the 2in valves from my LS1 heads and swapped them into the 862s and had a valve job and had the chamber’s unshrouded when I first built the LQ4 as a stock bottom end deal it ended up spinning a rod bearing so going back I planned on running some summit 2cc flap top 4.030” pistons and tbss intake to replace my stock LS1 intake and figured I’d port the heads to keep all air restrictions to a minimum. I’m in the process of working the intake port now and have been debating on removing or leaving the swirl ramp so thanks again for the input on that
JD: I was getting ready to order some 1.575 ex valves for my 862 heads and noticed that manley offers a 1.590 ex valve. In your considerable experience and expertise on these 862's, do you think there enuff exhaust seat to handle these?? I do expect to notch the cylinder heads walls to accomodate the 1.575/1.90? since my bore will be 3.898. Again, many thanks for your time and response. It is valued.
Personally I’d run either the oem 1.55” or a 1.57” max, you’ll have to unshroud any of them in the chamber to make the low-mid lift flow work. You can get 210+ cfm from a 1.55” valve consider how much you will need. JD
How critical is it for each port to have similar CC after working by hand on a street application? Throat & bowl along with exhaust exit/intake entrance profiles physically measured congruent between 16 port eagle 5.7 hemi head. Thanks for your time.
You want every port as close to the same as possible. Consistency from port to port is the goal! Try to work one area at a time on each head, this way you have better control and consistency in the work. Be patient and work slow making your work match. JD
I use my iPhone 11 with a tripod, I can’t hold the phone steady free hand. I also edit using my iMovie on the phone, I hope to step up to editing on a lap top one day. I can say in the past I’ve used my laptop to edit/upload a video, it takes a lot longer even to upload videos like that. JD
How much should I shave my ported 706 heads? I followed every step of your video. No before I install them how much would you recommend? I was told .30 to bump up compression I’m running a stage 3 btr cam.
@@joshuaobregon7932 If you have dishes Pistons I’d recommend milling .020”-.030” off the 706’s. Be sure to measure the lifter preload because milling will affect the distance. JD
Hey man, I'm running a set of 862 heads. All stock but with double cut valves. Will i have an issue with putting them on my ls1 build. With a 215/225 110.5lsa and .575 lift. Also running the truck intake. Thanks in advance
Did you mean your 862’s have Dual springs? You’ll need aftermarket valve springs If you’ll be running .575” lift. A lot of people run 862/706 heads to boost compression, as long as you’re not trying to make more than 440-450hp NA crankshaft it’s fine. The stock 862’s don’t support more HP than this. JD
@@HeadFlowInc the machineshop guy said and showed me how he cut 2 angles in the valve for more velocity he said. I'm gonna run them on my ls1 after seeing guys get 500+hp n/a with them on 6.0l. So i wondering what your take and advice it. If i don't 383 stroker then im gonna add a 78/75 turbo later.
No, unless you add material by welding the chambers or by surfacing/milling the heads to reduce the combustion chambers volume you won’t gain compression. Or run different pistons etc.
So far so good, with the stock valve job, 1.89” valve and 208cc runner it’s flowing 254 cfm @.600”. The port flows even better at high lift without stalling 268 cfm @.850” lift. I’m curious if adding a small back cut on the valve and doing a fresh valve job might help? Sometimes a multi-angle performance valve cut hurts flow. JD
I’m building a lm7 with the summit 8720 cam, want to add boost later on. I want to bump the compression up a little bit for better throttle response and power, how much would you recommend taking off? Or should I install flat top pistons?
@@Bassethoundswin Summit has a compression calculator , I used it and found it to be very simple to us & do to get the compression you want . I have 706 heads and the cam I used required 10.5 to 1 compression or higher . I had to mill .028 (I think) off the 706 casting . The stock intake did bolt on after milling .
Im in need of some help. Im currently going to be sending out my 706 heads out for a port and valve job, but I'm uncertain on what parts to use? I wanted to upgrade the valves to 2.00" but I'm confused with the exhaust size for the valve. Any help on recommendations or advice welcome. (Im working on a lq4 that will be stroked to a 408)
You can use 2.00” or possibly 2.02” valves but make sure the head work includes unshrouding the valves in the chambers or it’ll hurt flow. I’ve used both 1.55”& 1.57” valves, again unshrouding is paramount. With any port work the bowl/throat percentage will make or break the results! You might ask the company/person what percentages they use? Hopefully they’ll be familiar and able to help. I would go with a 89-90% intake port and 87% exhaust. 2.00” valve bowl/throat between 1.780”-1.800” max to be safe. 1.55” valve bowl/throat 1.3485” Email me if you have any questions or want a set of heads done etc. jeffdubray@gmail.com
The CID isn’t an issue, the chamber on the 862 were not intended to have larger valves. It’s just part of upgrading the 862 heads. Good luck keep me updated! JD
In my community tab I posted pictures of the flow data. I’m still tinkering with the exhaust flow and the head was flow tested without a stub pipe. Iirc the 1.89” valve with 208cc port flowed 254 cfm @.600 lift stair stepped up to 268 cfm @.850” lift. The flow would definitely pick up some with a fresh valve job and maybe a back cut on the intake valve.
You can tinker around with this simple math assuming steady state flow..... Dynamic flow in an engine would require extremely nasty differential equations that would look Japanese to the non-engineer.... There is a very specific dynamic port velocity for peak flow efficiency through a port. The port volume doesn’t matter, it’s the cross sectional area of the port that determines the velocity @ a particular flow rate. The head experts won’t share this number because it’s what makes them money....
@@HeadFlowInc friend and I had a gen 4 5.3 with 243s, beehive friendly torquer cam and a carb. Thing went mid/low 11s in a g-body malibu. I feel like the shrouding isn't as big of a hinderance as people think it is.
It can’t be as bad as reported or more people would be trying different combos. I have 2.00”/1.57” valves in my 862 heads on my Turbo 4.8. I did my heads before hearing about the cylinder shrouding issue; I wish there were back to back Dyno tests to at least verify if it’s actually true.
Years ago I bought a set of $50.00-$60.00 LS springs off eBay but couldn’t use them because I couldn’t find a retainer to fit them. The issue was where they cut the springs on each end made the I.D. an odd size, nothing would fit without grinding on the spring; there’s a video on my channel showing them. Valve springs have a harsh environment with a lot of strain put on them, I don’t think it’s a good idea to gamble in this area. JD th-cam.com/video/QJiVKRjfdm4/w-d-xo.html
Anytime you change a valve size requires a fresh valve job. I charge $750.00 to fully work the heads plus any machine work and/or parts needed for final assembly. I cover return shipping fully insured as well. JD
stop guessing and pick up a few porting books. Divide *flow* by *throat area* and that number should be similar between both valve sizes. A 1.89" valve would proportionately flow 273 cfm. port volume is not important inasmuch as it relates to area. I'd rather see dyno charts than flow bench charts.
I think you’re misunderstanding research and development of parts to improve power and efficiency. I’m not “Guessing” I’m testing to see what’s possible. How would I “divide flow by throat area” without having the port flow tested? Port volume is absolutely important to success when building a matched combination. Crysmatic, what’s your goal? Are you interested in learning something?
Already had them flowed, currently they’re flowing better than a stock 243/799 head with a 2.00” valve. Your name calling makes you look like a child. Thanks! JD
You’re right, it’s easy to misunderstand your intent. I have the flow data posted in the community tab on my channel. I’m still working on converting the data to digital. JD
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I would say the flow number would end up in the 270 to 280 cfm range as long as supporting chamber mods are done. Those chambers are very tight on the 1.89s and shroud the valves pretty heavily. I have a set of 706s I just finished porting and will have them flow bench soon.
This is some good stuff here! Love finding guys willing to share knowledge on this stuff thank you 👍 I’m currently building a 4.8 for my s10 blazer project!
If you can upgrade/use Gen 4 pistons and rods, this is the only thing I wish I had done different on my own 4.8 Turbo build. But if your building a moderate NA build under 7500 rpm you’ll most likely be fine with a Gen 3 setup.
Thanks for watching and the feedback I appreciate it!!! JD
Area of a circle and diameter of a cirlce are two very different things.
1.89" valve = 2.80insq of area
2" valve = 3.14 insq
2.165 valve = 3.68 insq
2.2 valve = 3.8insq
True, I’m referring to the width or diameter of a circle. There are applications for the area of a port if you were mapping out a new port or similar.
Thanks for sharing the area of various valve sizes! JD
Full of great information, but if I may say so without hurting your feelings, I felt like I was listening to my 10th grade chemistry teacher. Not the end of the world, I had some good times in that class in between droning lectures, haha.
Yeah I’m not very good at presenting and nothing is scripted or rehearsed. I would like it to be better than Chris from Family Guy though! lol
Another great vid, and I love to talk porting theory myself. I have done some of the same research, but on a 2.02 valve. The theoretical formula that I have used is one that I found on the web a few years back when researching the same thing that you are in the pursuit of researching. Throat area x115. In this case that formula would have this head at 266.8cfm max with a 1.7199 (91%) throat. Your work looks beautiful as usual and I'm interested to see what that small valve does on the bench with that nice port behind it.
I like the formula you shared! 266.x cfm is fairly close to my guess, in a way.
306cfm x .945= 289.17 x .9244= 267.30cfm
I’ll definitely keep your formula handy! Thanks for watching and the feedback I appreciate it! JD
@@HeadFlowInc Ummm, I'm gonna keep this formula handy too. I'm learning a lot here guys. Thanks!
Here’s an interesting comparison, using the theoretical formula of flow based on the area of the bowl. My 225cc ports use a 1.800” bowl w/2.00” valve:
Area 2.5434 x 115= 292.49 cfm
Area= 3.14 x r x r
r= Bowl size/2
My 1.800” bowl flowed 306+ cfm which shows you can exceed the formula. To find the actual multiplier:
306/2.5534= 120.311
2.5434 x 120.311= 305.99 cfm
This new formula is very interesting! JD
@@HeadFlowInc Hey that's interesting. The formula that I shared has that at 292.6. Ill experiment with yours on the next set of heads that I flow. Good stuff!
Love these videos! Thank you!
Mr. Headflow, a little more info on my build in my earlier email. The engine will utilize ported 862 heads (as you have described in this and other videos with 2.0 and 1.875 exhausts valves. Thanks again.
2.00”/1.57” valves, make sure to unshroud the valves by working the Chambers inside the head gasket bore size.
@@HeadFlowInc Thanks. Will do. The exh valves are 1.575. Sorrry for the mis-type.
Really appreciate all your videos on the 862 head.
No problem, just take the head gasket you plan to use on the 5.3 and use it to scribe or mark the bore opening because you’ll hurt flow if the chamber is covered by the gasket. JD
@@HeadFlowInc JD: Thanks for the response. Actually, I prefer to scribe the cylinder head with the final bore on the block so as to not create a step between the cylinder head and the cylinder wall esp since there can be quite a difference between the cylinder bore and the gasket bore. Just saying. Keep up the good work!
Good idea! Attention to the details will pay off. We try to run head gaskets as close to bore size as possible. Your method is good because a lot of people run gasket bore way too big. JD
Sounds good
Excellent stuff Jeff. Thanks for sharing. I'm very interested to see the results. I've been working on a set of 706's for an LQ4 and I want Manley ProFlo 2" intake valves but I'm trying to figure the gains vs cost. Gotta get the bowls cut anyway so, might was well step it up to the 2" intake valves! Very interesting.
Ultimately the 2.00” valve can flow more if the combo can use it. A max ported 1.89”/1.95” head would be a great street/strip 4.8/5.3 build, especially up to 550-575hp NA. Or a great torque head for a larger CID. JD
I'm also porting some 706s for my LQ4. I'm sticking with the stock size valves. Any recommendations for a good value valve in those stock sizes?
@@chriswise1232 Not trying to take anything away from JD here but, the most cost effective valve to use are the ones that came in your heads if they're reusable. Look for wear on the stem in the guide area. See something you dont like, get factory replacements. Rust on the seat area is a no go for me. Or, any rust for that matter. Those make for smoke in the long run. I'll use those for a cut-down I'll use for bowl cut templates. I may re-use a valve that has a stain from parts washing but, the stain goes away for me after valve lapping. If not, bottom drawer of the toolbox she goes. Back-flowing the valves makes a difference for a couple extra cfm worth of flow but, if you're running the factory size the added labor negates the gain.
The quality of your valve job itself (multi-angle valve seats), your machinist's quality of work and your bowl blending are the two most important areas to look at if your hand porting your own heads. For me, the bowl cut percentages you select and quality of your machinist's work come next along with port blending, consistency and repeatedness.
In a shorter response, the best economy valve for keeping the factory sized valve, is the factory valve. What makes the difference, as with any other is the quality of what you can throw at it.
I leave them factory and give all I know or if I go to a bigger size, I get the best I can afford.
I'm a huge fan of Manley ProFlo
Look at Summit Racing for cylinder head configurations, and the All on Cylinders Ultimate LS Guide.
I'd love higher port volume and valve size without screwing with the 61 cc chamber.
Remember Beneroulli's principle of venturi effect.
If I could get Rectangular port Heads with 61cc chamber with bigger valves I would get them.
Terry Wilkes has some heads on eBay. The 862’s are 227cc intakes rated at 308 @.600. And the 243s are 228cc and a little more cfm. Have you ever maxed out some 862’s ? I couldn’t imagine the gm castings are so much different you cannot do a 243 stage 20 on a 862 cast. But you tell me idk chit but what you or others have said
My 225cc intake ports flow 306+ cfm @.600 and outflow a stock 243/799 at all lift points.
This is with a 2.00” valve and a factory valve job zero back cuts on the valves.
Yes all the cathedral port heads can be ported to flow the same. JD
Mr. HeadFlow, I very much appreciate all your videos (long time subscriber). Kinda new to the LS scene. Am building a 5.3 with 7.820ish bore and 4 inch stroke for a street S10 manual. Would very much appreciate your insight and recommendation on cam sprecs for said engine. Thanks for your time and expertise.
I really like the new Summit 8720 cam, it equals the Sloppy Stage 2 cam at Peak but makes way more Torque throughout the useable rpm range.
.600/.600 @.050 218/227 adv 278/287 LSA 112
@@HeadFlowInc THANK you for your advice on cam and chamber work!
Just saw you’re in Raymore I’m in St.Charles Mo. Hi neighbor lol
Howdy Missouri neighbor! JD
Kcmo here
Porting a set of 862 heads for my 370ci LQ4, I was shooting for 460whp or better and was wondering if you could give me any tips. I’ve been watching your videos a lot and have found them very helpful by the way👍🏼
I’m thinking you are definitely going to need a 2.00”-2.02” intake valve, competition valve job and unshrouding both the intake/exhaust valves in the chamber.
88-90% bowl cut/blend
Swirl ramp removal
Valve guide boss reduction
Remove the rocker bolt lump.
To get 460 whp NA you’re going to need 550-60+ HP crankshaft. The crankshaft power depends of what type transmission you’ll use.
300+ cfm heads will definitely help!
We’ve found there’s even some issues with shrouding the stock exhaust valve on the 862’s because the chamber is so small it barely allows the exhaust valve to open. JD
@@HeadFlowInc Thanks for the info👍🏼 I took the 2in valves from my LS1 heads and swapped them into the 862s and had a valve job and had the chamber’s unshrouded when I first built the LQ4 as a stock bottom end deal it ended up spinning a rod bearing so going back I planned on running some summit 2cc flap top 4.030” pistons and tbss intake to replace my stock LS1 intake and figured I’d port the heads to keep all air restrictions to a minimum. I’m in the process of working the intake port now and have been debating on removing or leaving the swirl ramp so thanks again for the input on that
Cam
JD: I was getting ready to order some 1.575 ex valves for my 862 heads and noticed that manley offers a 1.590 ex valve. In your considerable experience and expertise on these 862's, do you think there enuff exhaust seat to handle these?? I do expect to notch the cylinder heads walls to accomodate the 1.575/1.90? since my bore will be 3.898.
Again, many thanks for your time and response. It is valued.
Personally I’d run either the oem 1.55” or a 1.57” max, you’ll have to unshroud any of them in the chamber to make the low-mid lift flow work. You can get 210+ cfm from a 1.55” valve consider how much you will need. JD
I’m still working on the upper cylinder scallop idea to see if it would work/help on a bore big enough. Excellent ideas and attention to detail! JD
@@HeadFlowInc JD, thanks for the voice of reason and experience!
How critical is it for each port to have similar CC after working by hand on a street application? Throat & bowl along with exhaust exit/intake entrance profiles physically measured congruent between 16 port eagle 5.7 hemi head. Thanks for your time.
You want every port as close to the same as possible. Consistency from port to port is the goal! Try to work one area at a time on each head, this way you have better control and consistency in the work. Be patient and work slow making your work match. JD
i got a question, what do you use to make your videos, your set up and stuff, im having a hard time holding my phone and doing stuff at the same time.
I use my iPhone 11 with a tripod, I can’t hold the phone steady free hand. I also edit using my iMovie on the phone, I hope to step up to editing on a lap top one day. I can say in the past I’ve used my laptop to edit/upload a video, it takes a lot longer even to upload videos like that. JD
How much should I shave my ported 706 heads? I followed every step of your video. No before I install them how much would you recommend? I was told .30 to bump up compression I’m running a stage 3 btr cam.
Depends on pistons, cam timing and head gaskets.
What pistons?
Which BTR cam?
What head gaskets?
@@HeadFlowInc stock pistons, motor is a 2004 5.3 specs on cam 218/224 .553/.553 110+0 ls7 lifters and mls gaskets
@@joshuaobregon7932 If you have dishes Pistons I’d recommend milling .020”-.030” off the 706’s. Be sure to measure the lifter preload because milling will affect the distance. JD
@@HeadFlowInc wow man you’re the best I’m only confident in my porting thanks to you. Thanks a lot! SUBBED
Hey man, I'm running a set of 862 heads. All stock but with double cut valves. Will i have an issue with putting them on my ls1 build. With a 215/225 110.5lsa and .575 lift. Also running the truck intake. Thanks in advance
Did you mean your 862’s have Dual springs? You’ll need aftermarket valve springs If you’ll be running .575” lift.
A lot of people run 862/706 heads to boost compression, as long as you’re not trying to make more than 440-450hp NA crankshaft it’s fine. The stock 862’s don’t support more HP than this. JD
@@HeadFlowInc the machineshop guy said and showed me how he cut 2 angles in the valve for more velocity he said. I'm gonna run them on my ls1 after seeing guys get 500+hp n/a with them on 6.0l. So i wondering what your take and advice it. If i don't 383 stroker then im gonna add a 78/75 turbo later.
How could you gain compression by porting heads? Is that a thing?
No, unless you add material by welding the chambers or by surfacing/milling the heads to reduce the combustion chambers volume you won’t gain compression. Or run different pistons etc.
Interesting.
So far so good, with the stock valve job, 1.89” valve and 208cc runner it’s flowing 254 cfm @.600”. The port flows even better at high lift without stalling 268 cfm @.850” lift. I’m curious if adding a small back cut on the valve and doing a fresh valve job might help? Sometimes a multi-angle performance valve cut hurts flow. JD
I’m building a lm7 with the summit 8720 cam, want to add boost later on. I want to bump the compression up a little bit for better throttle response and power, how much would you recommend taking off? Or should I install flat top pistons?
I can’t find the cam card information for the 8720; Summit has it listed as unavailable. I can’t recall what the Intake valve closing? ie ABDC
@@HeadFlowInc I posted a link but TH-cam deleted it. The cam is called the 8720r1 now.
@@Bassethoundswin Summit has a compression calculator , I used it and found it to be very simple to us & do to get the compression you want . I have 706 heads and the cam I used required 10.5 to 1 compression or higher . I had to mill .028 (I think) off the 706 casting . The stock intake did bolt on after milling .
My heads are done and on my 706 Heads on 5.3, the shop used your math and I have pics, how can I send them to you
Email:
jeffdubray@gmail.com
Im in need of some help. Im currently going to be sending out my 706 heads out for a port and valve job, but I'm uncertain on what parts to use? I wanted to upgrade the valves to 2.00" but I'm confused with the exhaust size for the valve. Any help on recommendations or advice welcome. (Im working on a lq4 that will be stroked to a 408)
You can use 2.00” or possibly 2.02” valves but make sure the head work includes unshrouding the valves in the chambers or it’ll hurt flow.
I’ve used both 1.55”& 1.57” valves, again unshrouding is paramount. With any port work the bowl/throat percentage will make or break the results!
You might ask the company/person what percentages they use? Hopefully they’ll be familiar and able to help.
I would go with a 89-90% intake port and 87% exhaust.
2.00” valve bowl/throat between 1.780”-1.800” max to be safe.
1.55” valve bowl/throat 1.3485”
Email me if you have any questions or want a set of heads done etc.
jeffdubray@gmail.com
@@HeadFlowInc thank you so much! This head is going on an lq4 that will be getting stroked to a 408. Im not sure if that makes a big difference.
The CID isn’t an issue, the chamber on the 862 were not intended to have larger valves. It’s just part of upgrading the 862 heads. Good luck keep me updated! JD
This pretty much answered my question. When making the throat bigger, do I used a double cut burr to open the seat?
👍
What was the outcome of the 862 porting?
In my community tab I posted pictures of the flow data. I’m still tinkering with the exhaust flow and the head was flow tested without a stub pipe.
Iirc the 1.89” valve with 208cc port flowed 254 cfm @.600 lift stair stepped up to 268 cfm @.850” lift.
The flow would definitely pick up some with a fresh valve job and maybe a back cut on the intake valve.
So how long until I can send you a set for porting?
Send me a message of what you have etc.
jeffdubray@gmail.com
You can tinker around with this simple math assuming steady state flow..... Dynamic flow in an engine would require extremely nasty differential equations that would look Japanese to the non-engineer.... There is a very specific dynamic port velocity for peak flow efficiency through a port. The port volume doesn’t matter, it’s the cross sectional area of the port that determines the velocity @ a particular flow rate. The head experts won’t share this number because it’s what makes them money....
Some 5.3s came with 2" valves
Yep, which makes it even stranger the GM engineers didn’t know about shrouding. I was shocked when I found out to. JD
@@HeadFlowInc friend and I had a gen 4 5.3 with 243s, beehive friendly torquer cam and a carb. Thing went mid/low 11s in a g-body malibu. I feel like the shrouding isn't as big of a hinderance as people think it is.
It can’t be as bad as reported or more people would be trying different combos. I have 2.00”/1.57” valves in my 862 heads on my Turbo 4.8. I did my heads before hearing about the cylinder shrouding issue; I wish there were back to back Dyno tests to at least verify if it’s actually true.
Have you are anyone else tried these I assume knock off pac 1219 springs from china on ali Express For like $70
Years ago I bought a set of $50.00-$60.00 LS springs off eBay but couldn’t use them because I couldn’t find a retainer to fit them. The issue was where they cut the springs on each end made the I.D. an odd size, nothing would fit without grinding on the spring; there’s a video on my channel showing them.
Valve springs have a harsh environment with a lot of strain put on them, I don’t think it’s a good idea to gamble in this area. JD
th-cam.com/video/QJiVKRjfdm4/w-d-xo.html
Do you have a shop? I'm in stl
I work out of my home in Raymore, Mo.
How much do you charge for in/1.89 exh/1.57 on 862 heads and full port and polish
Anytime you change a valve size requires a fresh valve job. I charge $750.00 to fully work the heads plus any machine work and/or parts needed for final assembly. I cover return shipping fully insured as well. JD
stop guessing and pick up a few porting books. Divide *flow* by *throat area* and that number should be similar between both valve sizes. A 1.89" valve would proportionately flow 273 cfm. port volume is not important inasmuch as it relates to area. I'd rather see dyno charts than flow bench charts.
I think you’re misunderstanding research and development of parts to improve power and efficiency. I’m not “Guessing” I’m testing to see what’s possible.
How would I “divide flow by throat area” without having the port flow tested?
Port volume is absolutely important to success when building a matched combination.
Crysmatic, what’s your goal? Are you interested in learning something?
Get them flowed,talker man. You can sit and guess all day, just get them flowed and then do a vid.
Already had them flowed, currently they’re flowing better than a stock 243/799 head with a 2.00” valve. Your name calling makes you look like a child. Thanks! JD
@@HeadFlowInc Is Talker man offensive?
You’re right, it’s easy to misunderstand your intent. I have the flow data posted in the community tab on my channel. I’m still working on converting the data to digital. JD
Spit it out.
Initial testing showed 247 cfm @.500” lift but they found a crack in the bore fixture. Repair and re-flow ASAP