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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: JohnnyPopper on January 05, 2019, 07:56:49 AM

Title: Mystery Compression Ratio
Post by: JohnnyPopper on January 05, 2019, 07:56:49 AM

I just installed a slightly used crate 350 in my K10, runs good.

I have no specs on the motor, came in a '80 I'm going through, former owner said it was fresh.

But I have a lingering question: can actual compression PSI measurements indicate the C/R?

Is there any data that shows what level(s) PSI would be, relative to that displacement?

Kind of backward engineering but it's not worth pulling apart to find out the mystery.

Any thoughts?

Title: Re: Mystery Compression Ratio
Post by: Ronno6 on January 05, 2019, 08:07:08 AM

Many variables come into play, but this article explains things:

http://www.healey6.com/Technical/Nominal%20compression%20pressure.pdf

In essence, cylinder pressure should be between 15 and 20 X the C/R.
That should give you an estimate.........

Title: Re: Mystery Compression Ratio
Post by: JohnnyPopper on January 05, 2019, 06:30:04 PM

Ronno6 you are the Man!!

Thanks so much, I'll post what I find.