Analysis of compression test results

[Benbrg]

Was looking for a second opinion for the results of a compression test for my 96 1.8. Had it sitting on the side of my house under cover since last April with the intention of swapping it into my Miata. The engine was very healthy while running in my now departed 96. Ran a compression test and the results came as follows:

4-145
3-130
2-135
1-160

None of the numbers are that low, but the spread worries me. A friend suggested that I need a new head gasket? So I am looking for a second opinion on whether these numbers are an issue and if so, what might be the cause for the spread. Thanks in advance, and forgive me for my engine troubleshooting incompetence.

[— kung fu jesus —]

Compression tests only tell you part of the story. A leakdown will tell you where the engine is losing compression. Redoing the comp test with a little but of oil added to each cylinder before testing them also help you narrow down the issues. A new HG won't help if the rings or valves are letting air through.

[Satisaii]

We go through a few engines here and I don't think I have seen one with compression numbers that low. At 175 cold, we would consider putting it in and retesting hot. That might be worth the hours of labor it would take to test it. Less than that and it is going to Mike Keegan for a rebuild. And yet, even with low compression, it probably ran fine and felt decent.

But I agree with KFJ. Do a leakdown. Borrow another compression tool and retest. Or test yours on a known good car.

[Benbrg]

Thanks guys. Definitely gonna do a leakdown.

[Tacky]

It I read correctly, this engine has not been run since last April? That makes it very difficult to take any compression readings seriously. Compression should be tested at operating temperature. A little rust on cylinder walls or valve seats may make a big difference in compression, but that might all clear out after it has run a few minutes.
The numbers themselves look crappy, you could consider pulling the head and having valves ground, but that is not a whole lot harder to do after it is installed. If I were you, I would gamble on it since it ran good last year. Install it, run it a bit and take another compression test.