first off...stock LS1...

what should the compression in PSI be on each cylinder?


second...

i have a misfire problem, think it's a bad lifter. it is intermitant...misses on cylinder 7 for a few seconds, then runs fine...then misses again...etc.

can i just pull the sparkplug, put the compression guage on it and run the engine to test compression? should i unplug that injector?

or should i just test it by turning it over with the starter?

i'm worried that if i just do the starter it could be reading the time when it seems to NOT miss...

if i run it i should be able to watch it fluctuate (assuming it IS a bad lifter) from proper compression to a period of bad compression.

any help would be greatly appreciated

 

I don't think you run the car to do a compression test. I believe you bump the motor over.

Can you pull the valve cover off and watch the pushrods move up and down? Making sure the lifters are moving correctly?

 

If a valve is bent though, you won't see it just by watching the valves and lifters moving. I don't think that tiny difference would be visible to the naked eye?

 

thanks guys..

did the compression test...

180psi on 3
170ish on 5 (sometimes missed on this cylinder)
000psi on 7 (major misses on this one)

so i guess it answers my question...bad lifter