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Boost/horsepower question (LS example)

General engine tech -- Drag Racing to Circle Track

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rewguy
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Boost/horsepower question (LS example)

Post by rewguy » Mon Oct 07, 2019 4:34 pm

Larry Meaux once posted.......that every cfm was worth very close to 4 hp at 15 lbs of boost.......and very close to 6 hp at 30 lbs. He said this proved itself time and again on his dyno....be it supercharged or otherwise. (i.e. all applications).
Given the current trend of stock block 5.3 and 6.0 LS applications running turbos......and making 1000+ horsepower with ease.....Wouldnt it still pay to put the best flowing head on possible?
I was informed that someone named John Buele (sp?) is really a front runner in this area, and he FULLY promotes small cathedral port heads over any of the bigger runner / higher cfm stuff that is out there. I guess he's set a couple records in this kind of racing. He's supposedly a somebody is what I'm getting at.
I'm having a "dispute" with some of my friends. I told them I'd still prefer more horsepower from having a superior head (Dart cnc'ed LS3 (370 cfm))......than the smaller stock cathedral ports (240ish cfm). I know the smaller head will recover from lag quicker if we are comparing the same turbo setup.......I know it will be peakier power with a larger head......But it will produce the same power at less boost, and keep the turbo cooler overall among other things. It wont be as likely to push head gaskets because it wont require the same cyl. pressure to make power......And racing eighth mile.....(and a tight field), If you have to get out of the throttle......you're likely to lose anyway. I also realize that a larger better flowing intake tract would probably benefit from two smaller turbos due to lag......but given two similar smaller cammed combinations......what would you choose if given the choice? My line of thinking is the combination with the better flowing head.

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ptuomov
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Re: Boost/horsepower question (LS example)

Post by ptuomov » Mon Oct 07, 2019 5:16 pm

What fuel? Knock limited or not?

rewguy
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Re: Boost/horsepower question (LS example)

Post by rewguy » Mon Oct 07, 2019 5:20 pm

no worry of knock. can use any available fuel. 11-1 compression. cam in the 240@.050 range, .630 lift. hyd roller

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ptuomov
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Re: Boost/horsepower question (LS example)

Post by ptuomov » Mon Oct 07, 2019 5:32 pm

rewguy wrote:
Mon Oct 07, 2019 5:20 pm
no worry of knock. can use any available fuel. 11-1 compression. cam in the 240@.050 range, .630 lift. hyd roller
My opinion is that if there's no knock limit and cooling is sufficient, then the best normally aspirated engine makes the best turbo engine, if the turbo is correctly matched for the application. Just an opinion.

Orr89rocz
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Re: Boost/horsepower question (LS example)

Post by Orr89rocz » Mon Oct 07, 2019 6:02 pm

Its all about where you want the power. Big heads need big cubes or big rpm. The runner shape of cathedral heads is different than square port obviously so the cc size difference can be misleading. Should also look at csa like anything else. Then intake to support the system and cam to balance the pressure ratios

The fastest lsx cars are not on cathedrals but there are manyyy fast cathedral port cars. All depends on what you are doing and the class rules etc

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Re: Boost/horsepower question (LS example)

Post by rewguy » Mon Oct 07, 2019 6:14 pm

No rules.......7500 rpm roughly, 370-400 cubes, cathedral msca - 2.57, ls3 msca - 3.1

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Re: Boost/horsepower question (LS example)

Post by BILL-C » Tue Oct 08, 2019 7:26 am

Why not use ported cathedral port heads that flow 300+ cfm? There are many shops (including myself) that will run a cnc program on your stock cathedral ports for $ 550.00.
Carlquist Competition Engines

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