compression testing

WIKEDZ · Post by **WIKEDZ** » Thu Sep 26, 2013 6:43 pm

just checked the compression of the l28 and not looking good.
can anyone tell me when i put oil in the cylinder and checked compression again, is 10psi enough of a increase to say the valve seal or hot valve clearance could be an issue.
all 6 cylinders increased by at least 10psi cyl 4 by 30psi i can remember the engine rebuilder i used saying he had done the hot valve clearances but now im not so sure because the engine wasnt running when i picked it up. (needed dizzy spark plugs etc)

thanks nathan

nzniggles · Post by **nzniggles** » Thu Sep 26, 2013 7:20 pm

Thought adding oil and rechecking tested rings, not valves

WIKEDZ · Post by **WIKEDZ** » Thu Sep 26, 2013 7:50 pm

does both. if reading does increase rings are suspect if reading remained low then valves are either sticking or not seating properly just wanting to know if 10psi is a considerable amount.

djz · Post by **djz** » Thu Sep 26, 2013 9:15 pm

What are the actual readings dry?

WIKEDZ · Post by **WIKEDZ** » Thu Sep 26, 2013 10:38 pm

without oil with oil

cyl 1- 140 150
cyl 2- 140 150
cyl 3- 140 150
cyl 4- 130 130
cyl 5- 140 150
cyl 6- 140 170

doesnt look the greatest does it
forgot to have the throttle open as well

ZMAD · Post by **ZMAD** » Fri Sep 27, 2013 5:31 pm

Do it again with throttle wide open as those readings mean nothing. Do each cylinder with same amount of cycles, say 3 times. Should be similar value, If not then add the oil to dig deeper.

nzniggles · Post by **nzniggles** » Sat Sep 28, 2013 3:59 pm

does both. if reading does increase rings are suspect if reading remained low then valves are either sticking or not seating properly just wanting to know if 10psi is a considerable amount.

True

WIKEDZ · Post by **WIKEDZ** » Sat Sep 28, 2013 6:16 pm

did the test again with throttle open got more even readings for all but cylinder 4 still sat at 135psi and same with oil
the rest of the cylinders were 155psi and 160psi with oil so not as bad as first thought but still bordering to low for cylinder 4
pretty sure manual says if lower than 128psi its rebuild time.

nzeder · Post by **nzeder** » Sat Sep 28, 2013 6:37 pm

Well the engine I plan to use in the track car has 140psi on all cylinders I have been told. I guess I should test it sometime.

This is just to get the car going, later on I will be rebuilding another engine I have then I will just swap out over a day.

us2 · Post by **us2** » Sat Sep 28, 2013 7:12 pm

Compressions look OK to me. Pretty consistent.

djz · Post by **djz** » Sat Sep 28, 2013 7:59 pm

I would check the valve clearance at least on that one cylinder if you are worried about it. Doing the valve clearances hot on a non running engine would be quite difficult.

ZMAD · Post by **ZMAD** » Sun Sep 29, 2013 10:03 am

Something happening in head then on cylinder 4.