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Doodle · Posted: Tue Jun 09, 2009 12:33 pm Post subject: My latest tale of woe.

I built my engine about 6 years ago. All the standard stuff. '81 head mildly ported, Schneider racing cam, Mahle 9.5:1 pistons, etc. It has worked well for about 6,000Mi.

A few weeks ago I took it out for the first time this year. She overheated. Checked the thermostat and found it to be lazy. Didn't begin to open til 85/86C. so I replaced it with one that opens at 82C. Took it out again and it overheated. This time the rad fan switch had given up the ghost so I replaced it.

Last weekend I drove it for around 5 hours in total with no problems. Starts and stops, full throttle, idle in traffic, everything was good. Then disaster struck. A few blocks from home, while accelerating from a light she suddenly started firing on only 2/3 cylinders.

I checked for spark first. Good spark at the plugs. I then checked the injectors and found them to be in order. Next was a dry compression test. 200PSI on #1, 180PSI on #2, 0PSI on#3 and 0PSI on #4 would appear to indicate a blown head gasket to me.

So where do I go from here? I'm working on pulling the head now. Obviously once it's off it'll go the machine shop to be checked for flatness. If it needs to be shaved this will be the second time that I know of. How much can be safely taken off before a standard head gasket will no longer cut it. What then?

Any other thoughts or considerations I should be aware of?
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Doodle
Pre 77.5 Mars Red

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Better figure out why it blew. I don't think an NA should go through one that quickly.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Make sure you didn't crack any valves.

That is what happened to me, the exhaust manifold was missing studs and nuts, so it cracked the exhaust valve on cylinder number 1 (which had no compression)

When I tried to correct the valve clearances, they wouldn't get close.

Obviously given the poor coolant flow inherent in the 924 engine, an overheat will likely cause a failure on #3/#4.

Though, I have to say any cast iron head with an aluminum cylinder head will likely pop the head gasket when overheated as the different expansion rates of the dissimilar metals will destroy the head gasket in short order.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

wombat · Posted: Tue Jun 09, 2009 2:46 pm Post subject:

Similar circumstances to my head gasket going, a small coolent leak when I first got the car which I fixed quite quickly (no real driving and did not show very hot at any time) but the gasket went whilst coming up to the lights on after about 10 min of driving. The fact that the starter would not stop cranking would not have helped however I think that the gasket had gone first because the only reason I needed the starter was because the car had stalled after running fine for the rest of the trip so I guess that this was the effect of the head gasket going. I had a major PITA trying to get my cam crank timing back because some spoon dick PO put the fly wheel on wrong finally having to do it using a positive stop method and still not 100% sure if this has worked. The rest of the head was rather easy, the only thing that was slightly difficult was the 4 plugs going different places with the same end so make sure you lable them I didnt and again I am still not 100% that they are all in the correct location.
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1977 924 2.0 Auto