90 GTZ Headgasket?

[GTU89]

Ok, i was gonna sell the GTZ a while back but I ended up backing out due to coolant starting to appear in oil. Runs as good as ever (I do not run it more than a few seconds, a minute tops to move it)

Do I seem right in assuming headgasket? It is to my understanding that the water pump can mimick these symptoms when it fails since it can dump into the oil since it is driven off the timing chain, is that right that it can dump into timing housing or was the person who told me this wrong? is the weep hole external?, I already bought a entire engine master gasket set and head bolts so it will be redone (cylinder head has almost no miles on it) my question is:

Am I being a fool going with head bolts versus studs?

This is all assuming the head is OK and not warped which I do believe it is but I will see for sure then, I will be doing the water pump too.
I may just replace the new timing set for insurance if budget allows since it is making noise again, should the cam towers/housing be replaced since from what I know they act as cam bearings?

Anything else that should be done while it is under the knife? I do believe I will just keep it since I have a good bit of money invested and it is a impressive ass car. If I can locate some I would love to do W41 cams and prom while it is ripped apart as well.

[DanteGTZ]

Here's what I would do to test for a head gasket problem:

#1: Compression Test (Cold)
#2: Compression Test (Warm)
#3: Block Test (kit available at Napa - will show combustion gases in the coolant)

These three tests will better tell if you do or do not have a head gasket (or cylinder head) problem. If you do - and you have to tear into it -I highly recommend head studs. They are relatively cheap ~$125 and are WELL WORTH IT on these engines.

[Rettax3]

Also on the older Quads like yours, a failed water pump will NOT generally dump into the timing case (external weep-hole). The newer Twin Cam engines do not have the intermediate bearing between pump and chain because GM wanted to save .43 cents and screw the engine's design up, making a WP job ten times more difficult. But yours is good, and you would have to have multiple seal failures to get coolant into the engine that way. Blown head gasket or warped/cracked head, most likely (common issue with Quads). As stated above, perform a block test (consider changing the oil first if highly contaminated just to save the bearings), especially if you can get it up to operating temp for the test. Good luck, nice looking car.

[Asylum]

Head gaskets are a known problem on pre '92 Quads and there was a factory re-call to have them replaced .

My '91 was done under warranty and replaced with a graphite gasket and 2* cam gears.

Not a problem since.

FWIW

[GTU89]

Huh, what I read was that the newer ones do not leak, and the first edition/first design leaked into the oil when bad.

I did pull the plugs and they appeared very dirty/black (usually they clean everything when coolant enters the cylinder) and it is not smoking/steaming. just loosing coolant into the oil. First thing I did was oil change, but the oil was quickly recontaminated. Did not dig any further though yet. Guess it could have blown in a way that it enters a oil passage or something though without typical symptoms.

Either way not a big deal, I have everything to do the headgasket except studs.

By the way, this is not on the original head or anything, head and stuff are around a year and a half oldnow with probably 4-5k miles on it, so if it blew I would bet that the previous owner did not torque the head correctly or something.

[Rettax3]

Hmm, a cracked head could still cause that too, depending on where it is cracked. Or a cracked block, but I can't recall ever hearing of a Quad block cracking -there is always a first though, unfortunately. Where did you read that the older W/Ps leaked oil into the engine? I would like to check that out... Maybe there is something I am missing on that. There may have been a first design and an intermediate design before the crappy 2.4 final design came out too... I am most familiar with the '92 Quad, since that is what I owned. Keep us updated, hopefully it isn't too major.

[DanteGTZ]

All DOHC Quads had head gasket issues - GM redesigned the gaskets over the years but it was still only a matter of time. My old 93 GTZ blew a head gasket around 90,000 miles. The new FelPro design and head studs make the Q4 HG failure a thing of the past.

FWIW: From 90-92 the GTZ got the "086" head - in 93-94 the GTZ got the 753 & 303 head - These heads had much smaller ports and valves in an effort to reduce cracking on the heads. This is most likely what most people are thinking of - They still had head gasket failures but the heads were reusable more often than not.

[GTU89]

I'll have to find where I read it if possible. You're probably right though, have not gone any further than looking at the plugs yet due to being busy with other things.

Plugs were filthy which further threw me away from head gasket combined with the lack of smoke, but probably smart to go into it expecting head gasket at the least

So:
Master engine gasket kit with head gasket (have)
Head studs (have head bolts but should get studs)
Water pump


Anything else? cam towers since they act as bearings? or just the stuff I listed?

Do the new water pumps come with a new sprocket? What brand of wp would you guys trust?

[Rettax3]

I'll have to find where I read it if possible. You're probably right though, have not gone any further than looking at the plugs yet due to being busy with other things.

Plugs were filthy which further threw me away from head gasket combined with the lack of smoke, but probably smart to go into it expecting head gasket at the least

So:
Master engine gasket kit with head gasket (have)
Head studs (have head bolts but should get studs)
Water pump


Anything else? cam towers since they act as bearings? or just the stuff I listed?

Do the new water pumps come with a new sprocket? What brand of wp would you guys trust?

WPs do NOT come with the intermediate drive -sprocket on the chain side, female spline on the pump side. The pumps are supplied just with the input drive (male splined shaft). If the pump you get has a sprocket on it, it belongs to the 2.4 Twin Cam, and will NOT work on your engine.

Check clearances on the cam housings -Plastigauge is your friend!- before condemning them unless you have good reason to suspect they are bad (visible scoring, low oil pressure MIGHT be an indication considering the position of the OPSU, etc). If you have new cams, new housings might be a good idea since line-boring the old housings is not a real option (no replaceable bearings). I would spend the money on the bottom-end first though, but if you want new towers and want to budget for them, go for it.

I like the 180 degree t-stat for those engines too, just because they are SO picky about overheating (usually), and you will be right in there doing the pump anyway... Quads come stock with 190 stats, which where I used to live at 9,000' above sea level, meant that the engine would start boiling over right about the time the t-stat began to open, if I lost pressurization for any reason.

How about doing the oil-pump too? I lost a set of bearings and crank on one of my old SOHC Quads because that !@#$! pump seized and ground its' phenolic gears off against the crankshaft...