I just picked up a car with an LS swap. The previous owner said it was bored with high compression pistons. He didn't build the car himself, so I'm assuming he was told this by the PO before him. So, without pulling the head off to see if they are indeed high compression pistons, is there any way to see if it does have high compression pistons? Would a compression test do the trick? If so, what kind of numbers should I look for?

Btw, I could care less if he lied to me just to sell the car. I would have gotten the car if it still had a D series. I just want to know if I can step down to regular fuel. I will continue to use premium gas until I find out for sure, just to be on the safe side. Not a big deal, I just went from using premium in a car that got 18mpg to this car getting low 30s

 

A compression test wouldn't tell you definitively. The only way to know for sure would be to remove the head.

 

They make cameras small enough to get inside the combustion chamber. I had a Milwaukee cam and loved it

 

a compression test would give you some idea. 220+ reading would indicate as such.

 

you cant get a real compression test without the motor not in the car with the starter connected... you can not do a compression test by hand.

 

Can't believe I didn't think of this. My step-dad probably has one of these.

And I didn't think a compression test would be able to tell me. Thought I would ask though.