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PostPosted: Sat Feb 27, 2021 5:52 pm 
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Just thinking out loud a little. I have @ 260HP at an 11.5 to CR. If I bump that up a point to 12.5 to 1, what is the HP increase I could expect. I did check on the Wallace Calculators and it literally said only 1 HP increase! :?
Can that be true? I just assumed that it would be more than that. If it is not then I'll never increase mine. Thanks for thoughts!

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PostPosted: Sat Feb 27, 2021 6:29 pm 
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It's diminishing returns the higher you go.

Try this one:

http://victorylibrary.com/brit/compression-c.htm

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PostPosted: Sun Feb 28, 2021 4:44 am 
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Thanks Ed. That one shows about 2.5% Change

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PostPosted: Sun Feb 28, 2021 6:15 am 
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Depends on other things you optimize for each CR, like ign curve, fuel type, induction, engine operating temp... But yes, diminishing returns as you go up. 2.5% sounds reasonable, although I bet you could get more if you do the work on other parts of your engine/operation.

Lou

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PostPosted: Sun Feb 28, 2021 6:18 am 
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Turbo EFI
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I am curious, at what static compression ratio should you start being concerned about head gasket sealing?

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PostPosted: Sun Feb 28, 2021 8:40 am 
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Quote:
at what static compression ratio should you start being concerned about head gasket sealing?


I had always heard keep it under 12 to 1 or you will start having issue. Therefore I am at 11.5 with the good Aussie gasket.

Ryan's car 11.00/118 mph, and has probably been run as hard as most racers will run, is at 13.3 to 1. He was running a MLS gasket on it and we had to pull the head and the only gasket we had to put back on was the Aussie gasket. It ran that full season (2019) and is still in the car right now. So in this case it will take more than 12 to 1. Your results may vary! :D :D

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PostPosted: Sun Feb 28, 2021 12:26 pm 
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Endurotec supposedly good up to 12:1. I imagine it can go higher, and you could use O-rings. I have run up to 11.1:1 w/mine.

Lou

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PostPosted: Sun Feb 28, 2021 6:27 pm 
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I believe higher compression makes more torque.

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PostPosted: Sun Feb 28, 2021 7:33 pm 
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Turbo EFI
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on a given engine, all else being the same, is there any such info about a CR increase on an "as found"/stock engine, or a recently (correctly) rebuilt to stock specs engine?

CR in stock form? CR upped a 1/2 a point at a time, to the limits of pump gas? how much of a power adder would "X" amount of compression, be?
looking at rough guesstimates, I know that adding different carb or FI, different manifolds, cams, or various amounts of porting, bigger valves, exhaust, start to play in at some point.... but if all a person did was pull the head, shave to a known extent, and reinstall, how much increase would they (POSSIBLY) get....

(not so much asking for me, but as often as a head shave is suggested/ and as often as "best performance upgrade" is asked around here by many, I'm sure those ask-ers might be wondering how much gain, for how much effort)


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PostPosted: Mon Mar 01, 2021 5:20 am 
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Dart270 wrote:
Endurotec supposedly good up to 12:1. I imagine it can go higher, and you could use O-rings. I have run up to 11.1:1 w/mine.

Lou



Endourotec can probably support 14:1 - I have run 13.5:1 on mine.

Greg

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PostPosted: Tue Mar 02, 2021 5:42 am 
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Good to know about the high CR on Greg and Ryan's cars. O-ring aid, or just plain gasket?

Lou

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PostPosted: Tue Mar 02, 2021 7:01 am 
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Plain gasket on Ryan's.

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PostPosted: Tue Mar 02, 2021 10:05 am 
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Dart270 wrote:
Good to know about the high CR on Greg and Ryan's cars. O-ring aid, or just plain gasket?

Lou



Just a gasket on ruster. No O Rings.

Greg

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