Compression test comparison

Hello,

I am not sure, but it has to be either the piston rings, or the valves getting more worn in. Maybe it wasn't done correctly the first time because it looks like the first reading cylinder number one is borderline and cylinders number four and number six are low. The second reading looks a lot better and almost perfect with very little variation.
Was the engine freshly rebuilt with the first reading?

Thanks,
Alex
2CarPros

I think about buying the car but if there is something wrong with the motor I will not buy it.

Hello again,

The second set of compression readings look good to me. I have included the specs for your vehicle's cylinder compression and compression ratio in the diagrams down below, and it looks great to me, all in specs and hardly any variation at all in cylinders at all. Like I said, I'm wondering if the first one was done correctly or not, but the second one looks great.

Thanks,
Alex
2CarPros

That's what makes me concerned about the two different readings? Both done buy two different mechanics. Maybe I should have the compression test done by again by a third mechanic.

Hello again,

If you want to do it yourself you can usually rent a compression tester from your local auto parts store, like AutoZzone, for free just leaving a refundable deposit. Then just go to link down below:

https://www.2carpros.com/articles/how-to-test-engine-compression

I have given you the specs from Chevrolet as what the cylinders should read. It's really simple to do and you don't have to wonder if it was done right or not because you will know it's done right. Then just get back to us with the results.

Thanks,
Alex
2CarPros

Good evening,

Just to add to the conversation, if it is the correct readings, carbon on the valve seats would cause the difference in the compression.

Running a top engine cleaner through the system would help it a lot and then retest it.

Roy

Thanks, the answer is going to save me from buying a big mistake.