Leak down and compression numbers in PPI.

[m962b]

In terms of buying the car, what's the general ranges of acceptability regarding both test?

Please forgive my ignorance.

[techweenie]

Generally you want compression numbers to be within 10% high to low. You want leakdown to be consistent but not beyond 7-9%, which is indicative of impending top end work.

I've seen many tests where the compression was decent but one cylinder showed a dramatic leakdown number. This is cause by dislodged carbon chunks getting trapped on the valve seat. Drive and re-test to be sure.