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Pump gas and Compression Ratio?


DSM1290

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compression ratio is not really the main issue....

 

its cylinder head and piston design that really limit what you can do (quench area)....

 

with the right combination of parts 12.5 and evnen higher compression ratios are possible

 

if your using mostly off the shelf stuff AJ is correct stay around 11:1

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The valve events can have more to do with the answer to your question than anything. Your asking what static compression ratio you can get away with on pump gas (SCR) when actually It's the dynamic compression ratio DCR that tells the real story. Cam overlap, bleedoff etc can allow a low enough DCR to allow you to run over 12:1 on pump gas. This Is a complex subject that is certainly beyond my knowledge, But i suggest you employ a true expert when trying to select components for an engine so that they truly work together.
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The valve events can have more to do with the answer to your question than anything. Your asking what static compression ratio you can get away with on pump gas (SCR) when actually It's the dynamic compression ratio DCR that tells the real story. Cam overlap, bleedoff etc can allow a low enough DCR to allow you to run over 12:1 on pump gas. This Is a complex subject that is certainly beyond my knowledge, But i suggest you employ a true expert when trying to select components for an engine so that they truly work together.

excellent advice.

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The valve events can have more to do with the answer to your question than anything. Your asking what static compression ratio you can get away with on pump gas (SCR) when actually It's the dynamic compression ratio DCR that tells the real story. Cam overlap, bleedoff etc can allow a low enough DCR to allow you to run over 12:1 on pump gas. This Is a complex subject that is certainly beyond my knowledge, But i suggest you employ a true expert when trying to select components for an engine so that they truly work together.

very true, theres a guy running around in a older nova, 14.5 to 1 406. drives it everday on 93 octane, and at the tracks drops in the race gas and turns the timing back up.

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I'm running somewhere between 30 and 32 degrees(IIRC) retarded, static timing. It's currently locked out because I don't have a vacuum advance distributor, but that's soon to come once I can source one compatable with the 4AG distributor.
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I'm running somewhere between 30 and 32 degrees(IIRC) retarded, static timing. It's currently locked out because I don't have a vacuum advance distributor, but that's soon to come once I can source one compatable with the 4AG distributor.

 

You do relaize that retarded is After top dead center, meaning that the piston would already be moving down the stroke before you fire the ignition.

 

Us silly V-8 guys tend to run our timing advanced, firing before TDC.

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