Compression Test Results

[Chuff]

Hey All,

A while back I did a compression test on my wife's car and I'd like some feedback on the results please.

The car is a Commodore VX Duel Fuel LS1 with 300K on the clock. The test was conducted on a cold motor and only a Dry Compression test was done.

I recorded a video of each cylinder test and then collated and graphed the data in Excel and the results are what we see below.

VX LS1 Compression Test Results.jpg

Anything untoward, or is it pretty much what one would expect on a 300K LS1?

Thanks.

Chuff

[immortality]

Looks fairly healthy, all pots at 160psi or better on a cold motor.

[Chuff]

Thanks immortality.

[immortality]

I'm no expert but consistent readings are always a good sign. Find a car manual and it should give you a guideline about what sort of cranking pressures you should see.

[Chuff]

So long as they're within 10% of each other is all good I believe.

What caught my eye was how they built up pressure. For some reason, the front cylinders of each head are up to full compression by the 2nd stroke, whereas the other cylinders, in particular, the left bank, need to build up to it.

I'm not sure but this may be expected seeing as it was a cold dry compression test.

Chuff

[immortality]

Maybe the first couple were dead cold, by the time you did a few tests a bit of heat in the rings from friction in the bores?

I've had compression tests done when purchasing cars and even on a hot engine they turn it over a few times to get full pressure.

[vlad01]

those first ones depend on what phase of the cyle they were in. you can actually see in the graph more or less the firing order and initial crank angle.

[krusty]

So long as they're within 10% of each other is all good I believe.

What caught my eye was how they built up pressure. For some reason, the front cylinders of each head are up to full compression by the 2nd stroke, whereas the other cylinders, in particular, the left bank, need to build up to it.

I'm not sure but this may be expected seeing as it was a cold dry compression test.

Chuff

A bone cold comp test isn't very conclusive. What you have there though is an excellent result for a cold engine. A leak down test will show truer reading on a cold donk.

That said, I'd be happy to go and throw a big turbo on an LS with compression test results like yours lol

[Charlescrown]

I see there are a few cylinders with worn rings. A thing not well known about a compression reading is how many revolutions it takes to reach the maximum pressure reading. A good engine will reach full compression reading within two revolutions. If it takes a few it indicates worn rings.