rb25 compression test results, need some advice

[syde_wayzzz]

ok so i did my comp test on my rb25 and it was done on a harbor freight tester....some cylinders had 120, some had like 155-160...should i be concerned about the 40psi diff or is it normal or what?...do u think i should have to rebuild it?...just need some suggestions

also note that this was done with no spark plugs in and cold

thanks

[rickgerhardt]

Thats a pretty drastic difference. You might wanna pop the head off and lap in the valves. If you can get ahold of a differential pressure tester then you can figure out if its leakin through the valves or past the rings. My guess would probably be valves though

[volcomskater773]

did you do it with throttle open? it makes a huge difference in rb motors. it will put you that low unlike a ka where it doesnt matter.

[rickgerhardt]

All compression tests should be done at WOT even a KA to get an accurate reading.