Quick Comp Ratio question

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Mar 15, 2002 | 08:42 AM

Taco

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Quick Comp Ratio question

How much should I Deck (correct terminology, right?) my heads for 11.0-11.5 compression?

Is that still safe for pump gas? How will that high a CR react to boost or spray if I ever do either in the future?

Thanks in advance guys!
Taco

<small>[ March 15, 2002, 08:44 AM: Message edited by: Taco ]</small>

Mar 15, 2002 | 01:33 PM

wizkid

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Re: Quick Comp Ratio question

I can't tell you how much to mill the heads to get that kind of compression ratio, but I can tell you that you would need 60 cc chambers to get a 11.03:1 compression ratio (CR).

Eric

Mar 15, 2002 | 03:49 PM

Taco

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Re: Quick Comp Ratio question

Well, that's better than nothing, so if it comes down to it, I can figure it out, unless somebody else can tell me.

Thanks!

Mar 15, 2002 | 03:54 PM

Pro Stock John

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Re: Quick Comp Ratio question

11:1 compression is okay for nitrous, bad for superchargers and turbos. For SC'ing and T'ing you would want a lower compression ratio, because the increase in heat from the forced induction would mix adversely with the increase in compression, end up needing a higher octane gas to 'cool' off mixture and avoid early explosions and mistimed explosions, call detonation.

Mar 15, 2002 | 03:57 PM

Taco

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Re: Quick Comp Ratio question

PSJ, that's what I have been told, so I was half-way expecting that answer. How about Pump Gas, will 11 to 11.5 be OK.

Any advice on the decking end of my question?

Thanks John!
Taco

Mar 15, 2002 | 04:09 PM

HONKY MOFO

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Re: Quick Comp Ratio question

The amount of compression you can run on pump gas can be affected by a lot of things. Cam overlap is a big factor. I would think that 11 to 1 would be fine on 93 octane as long as the LS1 has the reverse flow cooling of the LT1 engine. Not sure on this since I am new to the LS1 game, just got my car last week.

On a blown or turbo engine a drop in compression will also increase volumetric efficiency, effectively adding cubic inches to the size of the engine in addition to the addition from boost because the compressed air is forced in and fills the entire cylinder including the chamber and any dish area in the pistons.

<small>[ March 15, 2002, 04:13 PM: Message edited by: HONKY **** ]</small>

Mar 15, 2002 | 04:15 PM

Taco

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Re: Quick Comp Ratio question

OK, overlap is one thing I don't really understand. My cam is a B1 I think, .221/.221 .558/.558 on a 114 deg. LSA.

Is that a lot of overlap? any?

Thanks again guys, y'all are the greatest!
Taco