TR4 engine compression test

[dave bailey]

I've just done an engine compression test on my TR4 race car and found that it showed about 180psi on each cylinder, but when injected with a little oil, it improved to about 200 psi. I'm not sure if this is indicating a problem with wear, (or valve seats), and would benefit with a cylinder hone and new rings, or is about what should be expected. Any thoughts ?

[hoffman900]

Do you have a reference to what it was when the motor was first built and after it was broken in? Done cold? 
 

A huge jump between the two would indicate ring seal, but who knows where you’re at relative to where it was assembled. A leakdown test would tell you more considering you don’t have a baseline to compare to. 

[Lebro]

Those figures sound perfectly reasonable to me. There will always be some leakage past the rings, & oil will always reduce that. The main thing is that all the cylinders give readings in the same ballpark.

Bob

[Hamish]

Sounds good to me Dave. That sort of difference wet to dry is as Bob says is about right. 
 

they are high enough to suggest a higher compression  ratio too. 
 

[Motorsport Mickey]

+1 Sounds good.

After a fresh engine rebuild and break in is complete, a compression test with a note made of the compressions at least gives a reference point when checking compressions for faults in the near future.

Mick Richards

[Phil Read]

Compression testing with a little oil is the correct way to do it.

[dave bailey]

Thanks for the thoughts, unfortunately I can't find the figures from the last engine rebuild. Anyway I think that I will do a cylinder leak test and see what that shows.