[Hottarod]

If you turned over a motor by hand with a socket on the damper bolt what sort of compression reading would you expect to see on your gauge? It felt really tight so I pulled all the spark plugs to make it easier to turn. When it comes up on my test cylinder I can definitely feel it get hard but it only reads 50 psi on the compression gauge. Am I screwed?

 

[cam65fb]

It depends a lot on the cam you’re running. Static compression verses cylinder pressure. But still 50 PSI sounds very low. I would expect something closer to 110 to 150 psi. Your best bet is to test all the cylinders. The should all be within 10 psi of each other. If two cylinders side by side are low, I would suspect the head gasket. On the low cylinders, squirt some oil in and test it again. If the psi comes up than suspect bad rings. Good luck and hope you have not broken something major.

 

[GypsyR]

I did that once on a used motor, just for the hell of it. The highest reading I could manage without extra oil was 80 psi. I went ahead and put it in the car anyway. 3 years later and SWMBO is still driving it every day. I don't believe hand cranked compression readings are very useful.

 

[Hottarod]

They are all sitting at 50. I was hoping it might be something related to not being able to get the pop that the starter does when it turns the motor over. Its hard to get a good quick throw on it with a ratchet wrench. I left the gauge on and came in and took a shower and it was still on 50 when I went back out. I guess this would be dry too because the motor wasn't run for 2 months before I pulled it.

 

[Teebone]

Don't fret..it needs to be turned over several times with the starter to get a true reading...hand cranking doesn't work

 

[DMORRISON]

Teebone is right. Your not going to get much compression turning it by hand. The compressed air is flowing by the rings. Relax this is normal. You do a compression test with the starter turning the motor. It turns it a lot faster then you can by hand.

 

[roadracer]

I wouldn't worry about it without performing a leakdown test.

 

[johnpro]

I agree with the others, there's no way you can turn the motor fast enough by hand to prevent blow by past the rings.

 

[Axnjxn]

If it was holding 50 psi still when you came back after 10-20 min, it sounds find. You basically did a leak down test, and sounds like the valves are sealing fine. When you get around to it, throw the starter in and then see what you get.

 

[Guest]

YES YES YES. take out all plugs, crank over with starter several times and watch compression climb. It will max out after a few revolutions. Hand cranking IS not the way to do it.