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How Much HP, Per 1 Compression Increase

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Old Sep 5, 2009 | 11:25 AM
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Default How Much HP, Per 1 Compression Increase

I was wanting to know if there is a general rule on how much HP increase in one full point of compression.

So like 10.1 to 11.1 =?
or
10.1 to 10.5 to 1

Just wanted to see if there was a rule or specific HP Gain for the Compression Increase.
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Old Sep 5, 2009 | 11:35 AM
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You'll see estimates ranging from 3-4%.
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Old Sep 5, 2009 | 06:59 PM
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Thats Pat, is that for the full 1 compression gain?
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Old Sep 5, 2009 | 07:01 PM
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I've heard 4% as well.
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Old Sep 5, 2009 | 07:03 PM
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I was going to post a similar thread..haha

How much for .5 point increase in compression?

I'm trying to decide if I really want to mill the stock 799/243 heads... should bump it from 10.5:1 to 11:1.
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Old Sep 5, 2009 | 07:05 PM
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Ive always been told 3%.
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Old Sep 5, 2009 | 07:06 PM
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3% for what .5 or 1 increase?
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Old Sep 5, 2009 | 07:09 PM
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they say 3%-4% per 1 full point
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Old Sep 6, 2009 | 11:25 AM
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Actually gains decrease as compression increases. Diminishing returns.

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Old Sep 18, 2009 | 09:46 PM
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If that Otto Cycle efficiency chart is true, it looks like there is really not as much to be gained going from 8:1 to 10:1 on something like a 346 LSX. Assuming you make 346 hp on that same 346, it looks like there is up to a 10% gain in hp, going from 346 hp to about 380 hp, assuming heads and cam stay exactly the same.
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Old Sep 20, 2009 | 09:32 AM
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OK, maybe I'm not in the right thread but try this on for size. I have a stock 5.3 with the Edelbrock intake and carb setup. I want to put 317 heads and a radical cam and change the intake to a dual four. I have 6 pre set timing curves to work from. This is for an everyday driver "streetrod" 1955 belair. I'm fairly new to the ls series engines but I'm learning fast.
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Old Sep 20, 2009 | 02:55 PM
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Originally Posted by louisianagulf
OK, maybe I'm not in the right thread but try this on for size. I have a stock 5.3 with the Edelbrock intake and carb setup. I want to put 317 heads and a radical cam and change the intake to a dual four. I have 6 pre set timing curves to work from. This is for an everyday driver "streetrod" 1955 belair. I'm fairly new to the ls series engines but I'm learning fast.
Switching from 5.3 heads to 6.0 heads is a step in the wrong direction for compression. You are going from 61cc chambers up to 72cc's. You would be better off with ported 5.3 heads, or 243 heads milled to 59cc's (provided you don't run into PTV issues).
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