The 1947 - Present Chevrolet & GMC Truck Message Board Network - compression ratio on a stock 1985 C20 350

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G-NUT

05-31-2018 11:48 AM

compression ratio on a stock 1985 C20 350

Anybody know the compression ratio of a stock 350 from a 1985 C20?

Thank you.

Palf70Step

05-31-2018 02:36 PM

Re: compression ratio on a stock 1985 C20 350

Depends on what version you have. Anywhere from 8.0 - 9.5 to 1 compression ration.

Compression check numbers are normally about 180-190

G-NUT

05-31-2018 10:10 PM

Re: compression ratio on a stock 1985 C20 350

Thank you for the response.

Keith Seymore

06-01-2018 11:12 AM

Re: compression ratio on a stock 1985 C20 350

The LT9 was the base 350 engine for Federal Emissions. Compression Ratio was 8.3:1

There was also an LS9 available for California only. Compression Ratio was 8.2:1

https://www.gmheritagecenter.com/doc...olet-Truck.pdf

K

G-NUT

06-01-2018 03:25 PM

Re: compression ratio on a stock 1985 C20 350

Thanks for the info. I was looking into buying some heads and trying to decide between the 67cc or 76cc combustion chamber. World Products SR 170cc intake runner.

G-NUT

06-01-2018 05:06 PM

Re: compression ratio on a stock 1985 C20 350

Quote:

Originally Posted by Keith Seymore (Post 8272745)

Thanks for that. I found the spec on the link you left. I have the LT9, 350 (M). Showed me my bore, stroke, compression ratio, all kinds of good stuff.

I appreciate it.

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