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MG MGA - compression test

I recently had a compression test on each of the cylinders, and the result was 140psi.
However, I don't know what it should be.
Any ideas, and is the BHP for a 1600 Mk1
Nigel Munford


Actual reading doesn't really matter, what you are looking for with compression readings, is that they are all similar to each other.

Not sure about the BHP reading sounds about right, but there are two types quoted those taken at the flywheel and those taken at the rear wheels.


John Bray

The outer ones were 140psi. The two inner ones were 120psi. So, pretty similar.
Nigel Munford

1500 and 1600 High Compression engines (most were HC) as stock are happy in the 115-140 psi range for cranking compression. I'm happy if mine is anywhere near 125. 140 is rather optimistic, only for a new engine just run in, or one preserved in very good condition. The 1600-MK-II engine with high compression (most were) can be about 20 psi higher. If you see 170-175 psi it is probably a 1500/1600 engine with flat top pistons.

More important is that all four cylinders should be equal within about 10% to have smooth idle. Greater variation of compression readings cylinder to cylinder may also exhibit slightly rough running (small vibration) at higher speed with power applied.

For cylinders with lower compression you can do a blow-down test to discover what's leaking. See here:
Barney Gaylord

My Mk2 shows 160-170 over the 4 with original rebuilt 1622 motor -higher lift cam and lightened flywheel
P D Camp

This thread was discussed between 27/09/2011 and 28/09/2011

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