Hi I just did a compression test on a 95 diesel truck, the truck has different pistons than stock but i dont know what kind, they are suposed to be lower compression. i had an average number of 460psi on each cylinder but #3 was only 400. I squirted oil in each cylinder and every cylinder jumped up to around 520. what are the stock pistons supposed to make? how do I know if mine is ok? and is #3 Bad enough to worry about. thanks!

 

When it drops below 100 lbs difference, then you should worry. Stock pistons, with a turbo, make around 320-360. The lower compression coupled with the turbo prevents blowing out the head gasket. So I'd say your good to go.

 

yes you are fine rock and roll buddy

 

Thanks guys!

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If stock pistons only make around 320-360, and mine is supposed to have lower compression pistons, I wonder why I am seeing 460? thanks