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Compression test


tw205

Bronco II Rancher.
U.S. Military - Veteran
Joined
Jan 23, 2011
Messages
768
City
Bronson Michigan
Vehicle Year
1985
Engine
2.8 V6
Transmission
Manual
Total Lift
6” skyjacker 2” body
Tire Size
33x12.5
Im fix'n to do a compression test on my 89 B2 2.9. What is considered an acceptable pressure?
 
It depends on the age of the engine a good rule of thumb is within 5% of each other 10% max. Get the engine up to temp if possible with good oil in the engine. Pull all the plugs and test one at a time crank it until the guage stops moving Write each down as you do it and compare pressures. Also if it is running do a seafoam treatment if the pressures are uneven and then test it again. A vacuum guage will also let you know where the problem may be wether rings or valves. Post the results of your tests here.
 
Never came across an acceptable range as far as actual psi,but kimcrwbr1's formula is the proper one.Mine got 165psi as a low on one cylinder,about 180 as the high on one cylinder and an average of about 170 on the rest.

Don't forget to block your throttle valve open!
 

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