bought a used 5.3 from a 04 buick rainer for a transplant. i think these are 9.5/1 compression. hooked up compression guage & hand turned the engine, got readings from 90-110. that seems low, but i'm not really sure what to expect.

 

Not sure if there is a specific # that you should be looking for hand turning a 5.3L. Look for the highs and lows. If they're within about 15%, you should be OK. Any chance of hooking a starter up to it to spin it faster? A faster more consistant turning speed would make the #'s more meaningful.

 

No acurate data could be had from turning by hand but to get 90 psi by turning by hand is pretty good in my mind.

 

was trying to avoid wiring engine up by hand turning it over. went back out & wired it & using the starter i got 170-200 psi. thanks for replies.

 

170-200!!!! Good lord! I wonder the reading was so high?

I would have expected in the ball park of 140psi with no more than 10% variance between all the cylinders.

 

only 1 cylinder hit 200, rest were 170-185

dug in to gm service maual for this engine & it stated: "The minimum compression in any one cylinder should not be less than 70 percent of the highest cylinder. No cylinder should read less than 690 kPa (100 psi)"

would be interesting to hear what others are getting from their engines