Now people say that compression should all be within 10% of each other.

What if they are not? Say

170
140
160
140

Thats just a reference I made up. Mates is out soming like this but runs sweet as a nut and tunner said he don't know why it's out

 

Should do it dry and wet more than 3 times and take an average. Compression tests put the components under alot of stress and really should be checking cylinder leakage after.

 

Yea it was just dry test, underpowered tho. Suppose to be low comp pistons. Head looks mint and cvh34 cam is the cleanest I have seen as we know they love eating cams. Lifters are fine.

All I can think is...

Head skimmed to much?

The bottom end had three pistons put in but the old block was used and has score marks down the chamber, don't know if this will effect the comp.

Don't really want to go and chuck his engine over this as it runs nice just wants it's full power

 

New pistons not "three" lol iPhone!!

 

A leakdown test tells much more than a quick compression test.
Find a leakdown tester - they are quite reasonably priced.

LD tester will tell you if there are any cylinder leaks - and where they are coming from - valves, rings, etc..

 

Wouldn't that cause the car to run badly?