nrider42

Well I am pretty sure I blew a head gasket at the track yesterday. Sorry for the book but I wanted to provide enough information for someone in the future to help diagnose. The car is an early 1985 Euro 944 with 61k miles. It was running awesome on friday and saturday. It was really hot at watkins glen this weekend. Then sunday morning I started it up to head to the track and it wasn't idling very well. This car usually runs very smooth. I drove the 30 minutes to the track with no problem but after I let the car idle while in tech line, when I pumped the throttle I saw a little puff of white smoke behind me...odd. So I checked all the fluids and looked for anything strange. Nothing. Took it for a ride on the roads inside the track, got on it a bit and no smoke. Decided to go out for my first session and it ran fine, pedaling hard to keep up with the big boys. Checked everything over and noticed that there was some coolant in my catch bottle. I had an instructor who taught me to connect the coolant reservoir overflow hose to a catch bottle when at the track so I can monitor how much coolant is being lost due to expansion. Usually it equalizes after a couple of runs and I never see any more coolant in the bottle. However this time I had some more coolant in there....ugg. I decide to go out for a test run and the guy behind me says that there is a little puff of smoke out the tailpipe every time I shift...ugg. So I pack up and drive it home. While driving through the village, at every stop light there is some smoke out the back and then when I apply throttle it stumbles and more smoke out the back. White smoke. It cleared up as I continued to apply throttle and ran smoothly until I lifted off the pedal. I limped it home and put it in the garage.....and had a beer...or three.

I am good about checking my gauges when out on track and the car was running great, good oil pressure, good coolant temperature. The car never over heated. No sign of oil in the coolant or vice versa.

Pulled the plugs and the fuel pump fuse and this is what I found:

No 4 plug was wet
No 4 cylinder sprayed fluid out of it when I cranked the engine (no fuel pump)
Compression test was strange:
No1: 205 repeated
No2: 205 repeated
No3: 210 repeated
No4: 230, 215, 210
There was a bit of coolant around the rear of the head. This may have blown out of the cylinder during the compression test of the other cylinders...not sure.

So almost all signs point toward head gasket. The compression test results are strange to me but I have never had a blown head gasket before.

I am going to tear into it today....I always wanted to do a head gasket

If anyone thinks I am way off on my diagnoses or can explain the odd compression test results please post. Thanks!

nrider42

So I redid the compression test on a completely cold engine:

No1: 202
No2: 207
No3: 205
No4: 205

I am numbering from the front of the engine to the rear.

Yesterday the car had been sitting for a few hours so was not completely cold.

Is this making sense? Those compression numbers don't look like an issue. The white smoke and liquid in cylinder number 4 certainly are issues. Maybe it only leaks when it is hot?

V2Rocket

Compression is one thing, you should rent a leakdown tester, that will tell you.

That said, if the HG is original to the car, you got your money's worth

Tom M'Guinn

If the No. 4 plug was wet with coolant, and if coolant sprayed out that spark plug hole when you cranked it, then it's most likely a bad head gasket. Was the engine temp swinging up and down more than normal? Bad HG's let air in the cooling system, and trapped air creates erratic temps...

nrider42

It is interesting you mention the erratic temp readings....I was watching very closely on the way home and it started doing that in the last quarter mile.

Well I wasn't going to feel confident at the track in three weeks without replacing the head gasket so I tore it down. Here is what I found (see attached pictures):

No obvious hole in gasket...to my untrained eyes. But piston is steam cleaned.

Tom M'Guinn

Time well spent I'd say. Good job. I've removed plenty of bad HG's that looked (much) better than that. The sealing ring gets overly skinny and/or deformed with thermal expansion and age, then the combustion pressure gets through and pressurize the cooling system, then the high coolant pressure pushes back into the cylinder and steam cleans like that (and/or creates external leaks). Once the coolant finds a little pathway, there's not much you can do. I'd have that head skimmed and get a valve job while it's off. Will help it seal, and it looks like you are ready... You'll be good as new in no time!

951Dreams

Yeah, mine was like that. But I had water in my oil, and oil in my water. I'm about 99% sure mine blew, but I'll be darned if it looked it.

It's not uncommon on these, from the stories I've been told and what I've read, to hear of people having all the symptoms of a BHG without it looking blown once off. I have pics of mine running around here in my threads, looks just like yours.

The good news, most I read about are fine once put back together. So it seems they are blown, just not so you can tell. Weird that, but it is what it is.

EDIT: Tom posted while I was writing, but he's one to know, and confirms what I was saying. He even explained a good reason why. Great way of explaining it! Seems like he's right on the money to me.

nrider42

What does a valve job mean for this car?

Dougs951S

It means they'll machine the seats so they are flat on the valve mating surface and also concentric to the cross section of the valve's stem. Then, they will grind the mating surface of the valve face where they meet the seat so that they are also flat and concentric, and finally they'll lap the valves to the seat to insure good heat transfer and a gas tight seal. Also, have them check the head for flatness after they tank it, and don't have it skimmed if it's already flat since you wont gain anything in compression but you will retard cam timing.

thomasmryan

from other threads, remove the oil control valve from the head before you take it to the machinist.

Tom M'Guinn

Call me crazy but I'd skim it, taking off the least amount to get it clean and fresh. They just seal so nice when pretty and clean. Effect on timing/compression should be negligible, but if they have to remove more than a few thousandths you can always get the thicker factory gasket...

snb13

Mine's shaved .020". No need for a thicker gasket. I have the 4* cam key and Rogue's NA Tune. Love it. I don't believe the naysayers when it comes to shaving the head.

nrider42

OK....it is all apart and cleaned...I am ordering parts now. Head goes to machinist next week.

Who has experience with the wide fire ring?

I searched the hell out of it and...it is just like the oil and tbelt tensioning debates...opinions everywhere. Some say if you track the car go wide fire ring, some say you get a better seal with the standard.

This is a Euro motor and thus has higher compression.

This car is primarily a track car and gets run hard. Is the wide fire ring gasket a better solution?

Any 944 spec guys out there...what do you run in your cars?

Thanks!

Nate

thomasmryan

Look at the other options from Carl at 928 motor sports.

Tom M'Guinn

I run a widefire gasket, but I have O-rings that take advantage of the extra width. I think you will be just fine with either honestly, and that your head gasket preservation efforts would be best spent elsewhere -- e.g.., making sure you have a safe knock-free tune and as many sensor to monitor that as possible (AFR, Knock, EGT, etc.); a steam vent kit probably helps too and they're cheap. Cooler plugs for the track can't hurt. Good water-rich coolant with no air pockets or leaks (ever) too. Carbon-free piston tops and deburred head helps too... Raceware or ARP head studs allow for more torque and can help sometimes too. Good old MSD 6A ignition is cheap too and can help make sure you're lighting off every time... Just some ideas to consider....