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Old 05-31-2018, 11:48 AM   #1
G-NUT
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compression ratio on a stock 1985 C20 350

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

Thank you.
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Old 05-31-2018, 02:36 PM   #2
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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
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Old 05-31-2018, 10:10 PM   #3
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Re: compression ratio on a stock 1985 C20 350

Thank you for the response.
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Old 06-01-2018, 11:12 AM   #4
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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
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Old 06-01-2018, 03:25 PM   #5
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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.
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Old 06-01-2018, 05:06 PM   #6
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Re: compression ratio on a stock 1985 C20 350

Quote:
Originally Posted by Keith Seymore View Post
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

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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