What do these compression test resaults mean...

[doobs]

Ey all,

After suffering a bhg on my 7mgte, I have replaced the head gasket, im am now in the process of reinstalling the engine into the car, and I have got to a point where I can compression test it.

A bit of history on the engine before the results, it blew the old gasket between number 6 coolant gallery and the cylinder. It did not "die" just showed symptoms. I pulled the motor out, had the head machine (i was told he took 8thou off), all the cylinders and cylinder wall looked good. I used arp studs torqued to 80 ft/lb, using moly lube, and an acl standard gasket, with hylomar on both sides. I also replaced the injectors with 550cc's and will be using a lexus afm. The motor has not been started since I have replaced the gasket. This test was its first cranking...

Now the 1st compression test results:
1: 145 psi
2: 145 psi
3: 115 psi
4: 95 psi
5: 95 psi
6: 125 psi

Not good..... What could have happened?... all studs where tightened in equal increments to 80ft/lbs, both the head and block were not warped... could the rings have failed while sitting there... Is it possible Im loosing pressure out of the injector seals? or is it something more catastrophic...

Not to happy right now,

Cheers all

EDIT:
Went out and tested the low cylinders again: here are the results:

1: didnt test
2: 150 +5psi
3: 130 +15psi
4: 135 +40psi
5: 130 +35psi
6: 145 +20psi

Well im very lost now

[thechuckster]

injectors are not in the combustion chamber ... ignore them.

Three sources of leakage:
valve-seats, rings, gasket.

You can identify rings by doing a dry then wet test. You might be able to identify valves seal failure witha leakdown test. As for gasket - try pressurising the cooling system?

[BigBadBenny]

doobs,
It is quite possible that there is a fair amount of gum built up on the rings of the cyl's that are yeilding a high result, To find out if you've got stuffed rings, squirt some oil down the cylinders and do another test, if the results pick up then you've got worn rings. it's to late now since you've got the head back on to check the bores for scuffing and piston slap.
If the results don't improve, you may have valves that are not sealing 100% (possible tappe adjustment) or bad sealing on the head gasket,
I'd personly get it running before I really start pointing fingers at worn parts, and well if it's worn the it's worn, there's not much you can do to fix it.
Regards
Benny

[slide86]

also it can help to have the throttle open while doing the test to allow the maximum amount of air into the cylinder.

basically, do a wet test to determine the cause of the problem its gotta suck, specially after you have already got the engine in the car.....might need a re ring

[mrshin]

Get it going first, and drive it a bit. Every time I've ever checked an 'import' engine, the results have always been pretty ordinary, but then if checked a while later have been quite good. If it's still poor after some driving, then do (or get done) a leakdown test.

[BigBadBenny]

In reply to your retesting,
Oil does a lot more then lubricate the engine, it also seals.
Get the motor running and then start worrying if it needs to be done
Benny

[doobs]

Yeah I will get it going then see what happens...

Thanx for the replys, +1 rep for all

[Adam_Cressi]

fang it, push the cob webs out

[JustCallMeOrlando]

How long has it been sitting? As mrshin said, they sit around for a while, all the seals harden up and they test pretty damn ordinary. Get it warm, take it for a drive and heat cycle it. Do the test again and then worry if it's dodgy.

My car had a couple of cylinders that were totally stuffed, barely any compression at all. After driving it around for a while, they all came up around ~160psi cold.

[JustCallMeOrlando]

Note, even the cylinder that had no working injector came good.

[kingmick]

as said!give it a run and then retest. do a wet test aswell to make sure the reading are accurate.