SoCal Jet Boats

Tech Talk => Engine Mechanical / Electrical => Topic started by: Maker on July 22, 2015, 06:00:05 AM

Title: Pump gas compression
Post by: Maker on July 22, 2015, 06:00:05 AM

What is the max compression ratio for a pump gas iron headed Olds   I've have been told 9.5 on the low and as high as 10.75

Title: Re: Pump gas compression
Post by: mobboss on July 22, 2015, 06:42:10 AM

It depends, there are a few factors but let just say 11.1.  I have seen 12.1 work but outside temp was low.   At the point of 10.1 you really want to use some sort of additive.

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Title: Re: Pump gas compression
Post by: GT Jets on July 22, 2015, 06:43:48 AM

Quote from: Maker on July 22, 2015, 06:00:05 AM

What is the max compression ratio for a pump gas iron headed Olds   I've have been told 9.5 on the low and as high as 10.75

Somewhat depends on cam shaft selection and what is available as "pump gas".

I have always considered 10.5:1 as the upper.

GT

Title: Re: Pump gas compression
Post by: Maker on July 22, 2015, 06:49:57 AM

I'm looking at the Schneider baby solid flat  its 248-254 @ .050  .528 lift on a 108    I would like to be at or as close to 10.5 as I can  without having to spike the gas with race fuel