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Old 09-12-2018, 09:45 AM
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Default Cylinder head gurus (and salesman) join us!

Currently I am 700+ hp at the wheels through a m6 and strange 60, spinning the engine to 7100rpm. I am looking into aftermarket cylinder heads at this point. I have more than a few questions I would like advice on.

The basics of the setup are:
Ls1 block
Forged rods/pistons (9:1 CR)
CNC 243 heads 312cfm @ .600 lift with solid stainless intake/exhaust valves
Tick performance blower stage 2 v2 cam
LS6 intake
D1SC procharger @ 17 psi
Meth injection

This car is a street/strip build and I appreciate the low end grunt of cathedral ports but I understand that small bore square port offerings are available, not sure of their benefits though on a smaller cube motor like my 347. I am currently looking at the MAST 225cc small bore ls1 heads (killer sale on them right now!) with hollow intake/inconel exhaust valves.

Will these give me an appreciable boost in performance over my current CNC 243s? Also, is it worth the $ to upgrade to the lighter valves, I have heard that taking weight off the top end will help stabilize performance in the higher rpm ranges? I know other major brands have good choices as well (AFR, TFS, PRC), but is the difference between their similar offerings (225cc range) worth the $ difference? Finally, is 225cc going to be enough or should I be looking into something 235-245cc range?

Future proofing is also a consideration as well, I do plan to upgrade to an F1A in the (nearish) future as ive definitely maxxed my D1SC. Also, a 370 build is possible in the long-term. Will any set of heads I get for my current setup translate well to my future plans?

Any and all help is greatly appreciated!
Thanks 😊

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Old 09-12-2018, 09:51 AM
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In a boosted application, I don’t believe there is a good value in upgrading the heads. There are a lot of very good engine builders and even cylinder heads specialists that share the sentiment, but it depends on the application.

If it were me, I would save the money for the blower upgrade or use it towards a meth kit to lower IATs. Thats were your best bang for your buck will be.
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Old 09-12-2018, 10:05 AM
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Seeing as i already run 100% meth injection, i guess i could just go right ot the F1A, but i feel like im leaving some stuff on the table with mediocre CNC 243s. However, I am the first to admit that I do not know much about cylinder head intricacies.
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Old 09-12-2018, 10:07 AM
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I would focus on CFM and not be too concerned around port size and velocity since the boost is going to take care of that. I also wouldn't worry about lighter valves. I think there is more advantage in picking a cylinder header with a thicker deck surface and up the boost. Also get the exhaust as free flowing as possible which will decrease the boost but make more power. You also have the option to increase the compression ratio which will pay gains in power depending on if you're 93 with meth or able to run E85.
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Old 09-12-2018, 10:22 AM
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The most critical point to look at is air speed, not just cfm. Air speed/port velocity is what makes power. You only need as much CFM as the engine requires. Find out what the engine wants in terms of CFM and feed it that air as fast as possible. Be sure to eliminate restrictions in the intake path as well. Speed density tuned with a fast 102 and NW TB would make great gains across the board. I'd do that before aftermarket heads, then look into calling up the people who actually make the heads to get their opinion, since they see what combos work and what doesn't every day.

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Old 09-12-2018, 10:41 AM
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Originally Posted by Bspeck82 View Post
The most critical point to look at is air speed, not just cfm. Air speed/port velocity is what makes power. You only need as much CFM as the engine requires. Find out what the engine wants in terms of CFM and feed it that air as fast as possible. Be sure to eliminate restrictions in the intake path as well. Speed density tuned with a fast 102 and NW TB would make great gains across the board. I'd do that before aftermarket heads, then look into calling up the people who actually make the heads to get their opinion, since they see what combos work and what doesn't every day.
I have seen fast 102 setups be hit or miss when it comes to handling high boost. Seeing as i plan to upgrade to an f1a and go 20+psi in the near future, would it be worth it to spend the money on something that may provide gains but could also explode under high boost? At least worth it more than cylinder heads that would theoretically provide gains across the board?
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Old 09-12-2018, 11:27 AM
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Originally Posted by Bspeck82 View Post
The most critical point to look at is air speed, not just cfm. Air speed/port velocity is what makes power. You only need as much CFM as the engine requires. Find out what the engine wants in terms of CFM and feed it that air as fast as possible. Be sure to eliminate restrictions in the intake path as well. Speed density tuned with a fast 102 and NW TB would make great gains across the board. I'd do that before aftermarket heads, then look into calling up the people who actually make the heads to get their opinion, since they see what combos work and what doesn't every day.
This is on a boosted setup so most of what you posted does not apply. Air is shoved in the engine, not drawn in as in an NA application.
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Old 09-12-2018, 11:44 AM
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Originally Posted by ddnspider View Post
this is on a boosted setup so most of what you posted does not apply. Air is shoved in the engine, not drawn in as in an na application.

exactly
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Old 09-12-2018, 11:46 AM
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Originally Posted by KCS View Post
In a boosted application, I donít believe there is a good value in upgrading the heads. There are a lot of very good engine builders and even cylinder heads specialists that share the sentiment, but it depends on the application.

If it were me, I would save the money for the blower upgrade or use it towards a meth kit to lower IATs. Thats were your best bang for your buck will be.
Originally Posted by ddnspider View Post
I would focus on CFM and not be too concerned around port size and velocity since the boost is going to take care of that. I also wouldn't worry about lighter valves. I think there is more advantage in picking a cylinder header with a thicker deck surface and up the boost. Also get the exhaust as free flowing as possible which will decrease the boost but make more power. You also have the option to increase the compression ratio which will pay gains in power depending on if you're 93 with meth or able to run E85.

This..




OP if you want to turn more RPM's lightweight valve train is key. Low lash solid rollers, shimmed OE rockers and light valves would get you turning 8k rpm and easily keep things in check. But really, with your setup more boost is probably the best bang for buck at this point.
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Old 09-12-2018, 12:38 PM
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Originally Posted by 00pooterSS View Post
This..




OP if you want to turn more RPM's lightweight valve train is key. Low lash solid rollers, shimmed OE rockers and light valves would get you turning 8k rpm and easily keep things in check. But really, with your setup more boost is probably the best bang for buck at this point.

RPMs would be nice, hence the hollow intake/inconel exhaust upgrade i mentioned...
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Old 09-12-2018, 12:48 PM
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Originally Posted by snapdude View Post
RPMs would be nice, hence the hollow intake/inconel exhaust upgrade i mentioned...
And of course you could do light weight adjustable rockers, but holy chit are they expensive.

You've already got the bottom end for high revs (rods, rod bolts), and nothing sounds like a high revving v8. It just so damn expensive..
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Old 09-12-2018, 01:08 PM
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Originally Posted by snapdude View Post
RPMs would be nice, hence the hollow intake/inconel exhaust upgrade i mentioned...
FYI, inconel is a HEAVY metal. Itís more for durability under high heat conditions than RPM capabilites.
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Old 09-12-2018, 01:18 PM
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Originally Posted by KCS View Post


FYI, inconel is a HEAVY metal. Itís more for durability under high heat conditions than RPM capabilites.
Would that not benefit the high heat/cylinder pressures of supercharged applications?
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Old 09-12-2018, 02:27 PM
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You run the the best heads you can afford that will feed your motor what it requires on a N/A setup.. Boost doesn't change what heads you run on a engine, all boost does is make the charge more dense, therefore more power. DO NOT get the biggest ports you can find, this will slow you down, remember boost doesn't change the size / airflow demand the engine needs.

Last edited by SRT8.Acelleration; 09-12-2018 at 02:37 PM.
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Old 09-12-2018, 02:29 PM
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Originally Posted by ddnspider View Post
This is on a boosted setup so most of what you posted does not apply. Air is shoved in the engine, not drawn in as in an NA application.
This a common thought but is wrong.. Boost only changes air density and will not push more air/fuel into the engine, well maybe a little push may happen to a extent but the main power boost is from the air/fuel density. boost just makes the avalable air/fuel in the intake/heads more densely packed with air fuel and that is what adds the power... Ask Darrin Morgan about this, he will tell you the same

here is a whole podcast about it from his own mouth...

http://www.powerandspeedpodcast.com/?p=342

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Old 09-12-2018, 02:36 PM
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Originally Posted by SRT8.Acelleration View Post
You run the the best heads you can afford that will feed your motor on a N/A setup.. Boost doesn't change what heads you run on a engine, all boost does is make the charge more dense, therefore more power. DO NOT get the biggest ports you can find, this will slow you down, remember boost doesn't change the size / airflow demand the engine needs.
So along this line of thought 225cc would be about right for a max effort 346ci motor?
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Old 09-12-2018, 02:48 PM
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Originally Posted by snapdude View Post
So along this line of thought 225cc would be about right for a max effort 346ci motor?
If that is what the math says your engine needs then yes... there is a formula to calculate required cfm that you can find online, whatever that cfm number comes out to is what you will need, and remember, dont just look at peak cfm, look at what the head flows in the .300- .400 - .500 area too, the better the flow at low lifts is the better head as long as it still can support the needed cfm at .600.. I would listen to that podcast before you make any decisions on heads.
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Old 09-12-2018, 02:49 PM
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Originally Posted by SRT8.Acelleration View Post
This a common thought but is wrong.. Boost only changes air density and will not push more air/fuel into the engine, well maybe a little push may happen to a extent but the main power boost is from the air/fuel density. boost just makes the avalable air/fuel in the intake/heads more densely packed with air fuel and that is what adds the power... Ask Darrin Morgan about this, he will tell you the same

here is a whole podcast about it from his own mouth...

http://www.powerandspeedpodcast.com/?p=342
I agree that the more power you make NA, the more power it will make boosted. It does this due to FLOW, i.e. CFM's. Boost DOES make up for velocity....again air is forced in, not drawn in. Hence my comment. No podcast required.
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Old 09-12-2018, 02:57 PM
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Originally Posted by ddnspider View Post
I agree that the more power you make NA, the more power it will make boosted. It does this due to FLOW, i.e. CFM's. Boost DOES make up for velocity....again air is forced in, not drawn in. Hence my comment. No podcast required.
I understand what you are thinking, i thought the same thing for a long time, but after hearing from the experts I have changed my mind. Darrin has been doing this for over 33 years and has research to back all his statements... I will take his word for it over the internet masses.. Listen to the podcast and then comment on the way you think of boosted applications.
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Old 09-12-2018, 03:05 PM
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Originally Posted by SRT8.Acelleration View Post
I understand what you are thinking, i thought the same thing for a long time, but after hearing from the experts I have changed my mind. Darrin has been doing this for over 33 years and has research to back all his statements... I will take his word for it over the internet masses.. Listen to the podcast and then comment on the way you think of boosted applications.
I agree that there's plenty of bad information online, even from experts on podcasts I typically go with real world experience over theory as I've proven time and again to do things that people state simply aren't possibly by their models and simulations. Usually this is because you cannot accurately model every variable in a complex system and parasitic's come into play. Everyone is entitled to their opinion. Thankfully, as Stevie Turbo likes to say, you almost have to TRY to not make power on a boosted LS.

BTW, I haven't seen you actually post up anything you've built on here, have any examples?
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