lethal28

Okay im about to buy a non turbo with a rebuilt motor. How do i check the compression? What's good compression for motor? So do i check the leading or trailing for good compression. If i remember i think it was the top trailings. Am i wrong let me know. Help! I know i have to let it do 3 cycles around to get good compression. Anyone?

eriksseven

iTrader: (6)

You got it. Remove the EGI comp. fuse in the underhood fuse box to disable the fuel-system. Then remove the trailing (top) plugs and install the compression tester, secure it tightly. Then while you watch the gauge, have a friend get in the drivers seat and 'crank' the motor while you watch. Make sure you tell your friend to hold the accelerator pedal on the floor while he cranks, to get the most accurate results.

To allow the needle to bounce freely you'll either have to hold down the "button" on the tester (which allows the pressure to be released and the needle to bounce freely) or remove the little 'check valve' which can be unscrewed from the tip of the tester.

You'll want to see numbers of around 100+ PSI.

Also, you'll want to do the test after the motor's been warmed up. Cold compression can be slightly misleading (higher).

fast86rx-7

i was told by mazdatrix that you want to see 90-120 at sea level so if you are at higher alt. it may be lower

JoshRX7

iTrader: (5)

I'd be looking for 100+ like Erik told you. Mazdatrix has a good point with higher altitudes... not sure to what degree, however.

stevensimon

iTrader: (11)

i'm at 5200 feet and on my fresh rebuild i pulled 95-100psi.

91verty

95-100 is probably more like 105-110 with the type pf tester your using. Typically, these testers are not as accurate but if you are getting 95-100 you are in excellent shape my friend. Just break it in properly.