low compresion results where to go next

[RiyadYar]

cylinder 1 100psi
cylinder 2 120 psi
cylinder 3 110 psi
cylinder 4 117 psi
cylinder 5 110 psi
cylinder 6 110 psi
..decided to do a compression test to try to figure out if valvestem seals were causing blue smoke when shifting gears at high rpm or turbo seals and came up with these results. the first cylinder i tested had the cps connected could this cause such low readings ?
my plan is to put it back together re-time it and rerun compression tests. Do you guys recommend anything else to pinpoint the culprit before i do this ..

p.s i rented the compression tester from autozone one of the orings looks chewed up could this also be the cause? the first one i exchanged didnt have the check valve in it.

thanks

 

[jake8790]

The CPS has nothing to do with compression test results.
Of course the tester can't have any leaks.
Did you test with the throttle fully opened?

 

[RiyadYar]

the last three cylinders the throttle was fully opened which still came out low. could it be from bad valvestem seals ? or is it more likely bent valve, lash adjustment.timing, pistonrings

 

[Amtrack]

You can verify the rings with a little bit of engine oil into every cylinder.
It will seal the rings better if they are worn.
With conspicious better results, it should be the rings.

Valstem seals won´t affect compression in any way, as they are not in the combustion chamber.


Have you checked the valve clearances?
If it is set too wide, you will loose compression too.

 

[1988ma70supra]

You can verify the rings with a little bit of engine oil into every cylinder.
It will seal the rings better if they are worn.
With conspicious better results, it should be the rings.

Valstem seals won´t affect compression in any way, as they are not in the combustion chamber.


Have you checked the valve clearances?
If it is set too wide, you will loose compression too.

+1

Doing this wet test will rule out your bottom end. After that is out, your left with either your head gasket or valves. You can rule out the valves by doing a leakdown test

 

[jetjock]

... could it be from bad valvestem seals ?..

Not a good sign...

 

[Dan_Gyoba]

the last three cylinders the throttle was fully opened which still came out low. could it be from bad valvestem seals ? or is it more likely bent valve, lash adjustment.timing, pistonrings

First off, re-do it so that all 6 cylinders are done with the throttle fully open.

A chewed up O ring could cause low readings if that O ring is sealing anything on the compression side.

Things that can cause consistent low readings across all cylinders are actually fairly few, most of which I can think of aren't really problems either. Bent valves TEND not to happen in all cylinders, and definitely not evenly.

The tester leaking, the starter cranking slower than expected (TSRM specifies 250 RPM) will both do it for example.

<OPINION>I was always taught that the biggest thing that you're looking for in a compression test is a large difference in one or two cylinders from the rest. The 20 PSI difference between cylinder #1 and #2 would be the thing that concerns me, though with the average being near the middle of the two, I don't know how much. I would retry the test, making sure that conditions are as close to identical for all 6 cylinders as possible, then retry again with about 1cc of oil squirted to the side of the cylinder to check ring conditions.</OPINION>

 

[RiyadYar]

I havent checked valve lash clearances but the head was rebuilt when I did the head gasket job about a year (arp studs properly torqued, felpro gasket) I would imagine they checked it but I will verify for myself. Starter is new along with battery. I will try to exchange tester
for another one and redo test dry and wet. Jetjock do you say this because the valvestem seals dont deal with compression only keeping oil out?

Shoud the tester just screw in hand tight I find it hard to get the tester in very tight unless I use a long nosepliers in awkward angles.

 

[RiyadYar]

I havent checked valve lash clearances but the head was rebuilt when I did the head gasket job about a year (arp studs properly torqued, felpro gasket) I would imagine they checked it but I will verify for myself. Starter is new along with battery. I will try to exchange tester
for another one and redo test dry and wet. Jetjock do you say this because the valvestem seals dont deal with compression only keeping oil out?

Shoud the tester just screw in hand tight I find it hard to get the tester in very tight unless I use a long nosepliers in awkward angles.