Compression test questions

[Turbo Monk3y]

Real simple, can you do a compression test on the 4 cylinders with the long block out of the car not hooked up to a starter??? Meaning maybe manually cranking the motor clockwise or something??? The reason im asking is because i just picked up another 6bolt motor for a friend it has 70K original miles and ran perfect before it was taken out of my neighbors wrecked car.... i just wanted to do a compression test for the hell of it and wanted to know if its possible with the motor out of the car on an engine stand..... Thanks

 

[ForcedInduction]

Nope, you would need cranking RPM to get accurate results. If the starter is installed you could prolly connect a battery and jump the starter or you could do a leak down test.

 

[1fast97gsx]

the only way I could see is taking an impact gun to the crank pulley bolt and cranking up the pressure and the speed of the gun. Then hold the trigger for a while and see if the guage moves. I doubt that would even work but it'd be easy to try.

 

[Maglin]

the only way I could see is taking an impact gun to the crank pulley bolt and cranking up the pressure and the speed of the gun. Then hold the trigger for a while and see if the guage moves. I doubt that would even work but it'd be easy to try.

Bad idea... You will way overtorque the Harmonic dampiner bolt and maybe break it off... Just do a leakdown test... It's a better idea of how it's sealing anyways...

 

[Blue92]

Yeah, don't motors cold motors give low compression numbers too. Not really a good idea. A leak down test would be nice.

 

[1fast97gsx]

Bad idea... You will way overtorque the Harmonic dampiner bolt and maybe break it off... Just do a leakdown test... It's a better idea of how it's sealing anyways...

yea I agree leakdown is better

 

[92tsifwd]

That is what I did and it worked for me well. I was not shure what to turn the air compresser to though so I just did 60psi and found it that way. I wouldn't turn the pressure up too high.