ok i just changed my head on my ls motor. i have a 90 ls and just put a 05 head on it. before i put the head on it tha comp was 185 across the cylinders. now its
170, 140, 125, 170. then i put oil in the cyl that read 125 and jumped to 160! so i dont know how the compression dropped so much. any ideas? thanks. -Dale-

 

leak down test is the best indication of internal condition...good luck man

 

double check ur timing u may be a tooth off or more.

by the way did u really mean o5 as in 2005?

 

opps. no i meant a 95

 

double check ur gauge before u pull that head.
try another gauge or try it on other cars