How much compression would I gain
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,340
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From: Moro IL
How much compression would I gain
Next year I'll probably be swapping heads on my LS-4, the main goals being dropping weight and increasing compression from the dismall 8.25:1. Stock 049 heads have a 122cc chamber. I'm looking at the Performer RPM aluminum oval ports which have a 110cc chamber, how much would this raise the compression ratio :confused: Thanks for any help as always.
:cheers:
Pat Kunz
:cheers:
Pat Kunz
Safety Car
Joined: Oct 2000
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From: Allen TX
Re: How much compression would I gain (73 LS-4)
Hey Pat,
I've researched this a lot, too, since I have 8.75:1 CR with 118cc chambers.
From everything I've gathered, 14cc = 1 full point of compression. So, in your case 12cc = .857 gain in compression. Not bad! :)
I've researched this a lot, too, since I have 8.75:1 CR with 118cc chambers.
From everything I've gathered, 14cc = 1 full point of compression. So, in your case 12cc = .857 gain in compression. Not bad! :)
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,340
Likes: 2
From: Moro IL
Re: How much compression would I gain (WA 2 FST)
Thanks WA 2 FST, that would put me about where I want to be (at least 9:1) plus drop about 80lbs of weight and give me a better choice of cams to go with. Too bad my 049 heads have such large chambers becouse they flow really well. I believe i read in chevy high performance when they took a given engine and just changed the compression ratios on it, it was losing or gaining about 12-14% of its power per point of compression, of course there are a lot of factors here but even a 10% gain is quite a lot.
Thanks
:cheers:
Pat Kunz
Thanks
:cheers:
Pat Kunz
Race Director
Joined: Apr 1999
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From: CORVETTE 77 385 C.I. TEXAS
Re: How much compression would I gain (73 LS-4)
In general:
I suppose this chart needs some explanation. It shows the increase in power in % of a C/R increase. EXAMPLE: If the original CR is 9:1 on right of chart & it is increased (A line) to 12:1 (B line) on left of chart, then the increase in power is about 4.5%. If the power is increased from 9.5 to 10, the increase is about .08%.
I suppose this chart needs some explanation. It shows the increase in power in % of a C/R increase. EXAMPLE: If the original CR is 9:1 on right of chart & it is increased (A line) to 12:1 (B line) on left of chart, then the increase in power is about 4.5%. If the power is increased from 9.5 to 10, the increase is about .08%.
Thread Starter
Melting Slicks
Joined: Jun 2001
Posts: 2,340
Likes: 2
From: Moro IL
Re: How much compression would I gain (Ganey)
Thanks Ganey,
According to the chart I'd be gaining less then 2% :cry , a far cry from the article I read. Thanks for the info.
:cheers:
Pat Kunz
According to the chart I'd be gaining less then 2% :cry , a far cry from the article I read. Thanks for the info.
:cheers:
Pat Kunz
Safety Car
Joined: Oct 2000
Posts: 4,080
Likes: 565
From: Allen TX
Re: How much compression would I gain (73 LS-4)
Thanks Ganey,
According to the chart I'd be gaining less then 2% :cry , a far cry from the article I read. Thanks for the info.
:cheers:
Pat Kunz
According to the chart I'd be gaining less then 2% :cry , a far cry from the article I read. Thanks for the info.
:cheers:
Pat Kunz
One thing to remember is that the gain in power is based solely on CR changes. Obviously, you'll be able to run a more aggresive cam with the higher CR and I bet those heads flow as well or better than your 049s at the lift you plan to run and in the rev-range your engine is designed for.
