Thread: compression test on my old 350...

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Hi Folks, I just did a compression test on my old 350. Borrowed the gauge from a car shop, so it's readings are very possibly correct. This is what I got, I did the test twice (three times on the weak cylinders) and always got the same result, so it probably won't be a measuring error. The passenger side head gasket is blown, when I crank it over water sprays out of the spark plug hole
The engine doesn't run all too well and as I mentioned before, it doesn't respond too well to timing adjustments (wouldn't with 3 cylinders dead)
What do you think it is? Doesn't look like the piston rings to me, I would guess it's just the gaskets...

With one bar equalling 14.7 psi @ sea level, the motor is generating at least 11 bar (161.7 psi) on five of the cylinders. If it were rings, all cylinders would be weak unless you've let the motor detonate. In that case, some of the rings could be broken or pistons could be disassembling themselves.

Looks like it's time to get your tools out.

Hi Tech,
yeah, was time to get my tools out: 30cc of water in one cylinder and cross-talk (burnt gasket) between #3 and #5 cylinder. That possibly explains the weak compression on 3 and 5, #4 was the one full of water. Think I might get the heads fluxed, but I'll have to clean them first.

Just wondering about my engine in general, it's already bored .060 over, but the cylinder walls look OK, and judging by the compression being OK on the 5 other cylinders I guess it's still useable.

I'll get the heads cleaned tomorrow, there's a hole lot of carbon and gunk in them, guess I might play with my carb a bit, seems to be running rich...

Thanks in any case, I'll get in touch as soon as I know more...
Mad