Compression ratios and PSI

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SHyslop
Posts: 115
Joined: Thu Dec 30, 2021 4:17 pm

Compression ratios and PSI

Post by SHyslop » Fri Feb 14, 2025 4:51 pm

One of my winter tasks was to test the compression ratios on one of the cars. While that gave me four readings, what I didn't have was the means to compare them to what the standard should be for that particular car. I had a look at the workshop manual but I didn't see any details for this so, with the aid of an online calculator, I have arrived at the following figures for the various compression ratios of the 1934-47 cars, rounded up to whole numbers.

Compression ratio ....... PSI
5.7:1 ....... 84
5.9:1 ....... 87
6.1:1 ....... 90
6.25:1 ...... 92
6.5 .......... 96
6.7 .......... 99

Hoping this may be of some interest . The CR figures by engine are on pages 14/15 of the workshop manual.

GOY189
Posts: 586
Joined: Sun Oct 19, 2008 5:08 pm

Re: Compression ratios and PSI

Post by GOY189 » Fri Feb 14, 2025 5:47 pm

Many thanks Simon
Mike Maher

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