zerMATT951

Look at about 5:30-ish on the head - looks like some extra corrosion right there... coolant probably ate through the compression ring on the gasket.

Wow... what a mess...

silverBean

Holy mother of...!!!! that twinges my heart strings. not twinged, tore!!! sorry

nine-44

My dad's 951 had the engine apart when we bought it. The #4 was scored severely, the material ripped from the cyl. wall was deposited on the piston top and being compacted against the head. I suspect that it was severely overheated, not sure. The rod, crank and cyl survived minus the bad scoring, no cracks and the piston wasn't cracked either. I'm throwing a vote for hydro lock, either gas or water. If an injector was to stick open it may dump enough fuel to foul the plug and build up in the cylinder. Or possibly a bad injector, running lean, lost the head gasket and filled with coolant? Are all the AFM bolts there, they are the only internal bolts in the system that could make it to the cyl.

Danno

"It looks like FOD (foreign object damage) to me. Look at the amount of damage to the head. It looks like there was something bouncing around in the combustion chamber for a while. That kind of damage doesn't happen in an instant."

That would be pieces of the piston. Kinda like what happened to Turbite's engine a year ago. In his case, the piston completely disintegrated and there were no remains to be found. This looked like the headgasket corroded on the #4 cylinder and leaked coolant into the cylinder. Most blown headgaskets have been on the #4 cylinder. I suspect due to it running slightly leaner. Also probably also due to the compressing-ring on the gasket not having full support all around. On the #4 cylinder, there's an extra large hole for the coolant passage, which provides less material around the #4 compression ring.

Zero10

I wonder if it couldn't be a fuel injector, like was mentioned earlier. I wonder how fast that would dump gas into the cylinder?...
Were there any indications before it happened?

I've never seen a head gasket go bad and allow that much coolant into a cylinder in such a short time. Maybe if the block failed first, but not from a head gasket.

shmark

Looks like long-term corrosion and a water problem. Either the piston weakened or a sudden influx of water caused a hydrolock. Did you find any pieces of the piston top? That head looks badly pitted all around the pistons, and the #4 chamber is toast. Clean it up and use it for a wall ornament.

Dal Heger

I can't believe it was hydrolock. He said it was running at the time. This did not happen at startup, and there is NO WAY that a trickle of coolant at 3000 rpm could cause a hydrolock condition. There has to be something else that went wrong.

Still I'd love to figure out what went wrong.

Dal.

F18Rep

Thanks all for the interest... I will try to get more photos of the piston pieces from Doug and maybe of the cyleinder walls too. But no, it was not at start-up. The engine had a belt change but was idling OK and even drove ok for a few miles. I don't think he even had the the radiator opened - just change the belts. Now there is one other symptom, that I should ahve mentioned, he was first interested in the belts because of a vibration. Thinking was then that maybe the balance belt had slipped. And by the way this is no beater, Doug has had quite a bit of work done to get the car in good condition. I will try to shame him into coming in and telling his story. He seems to think he is the only one who has ever spent a lot of money on an old Porsche. For us, this is NOT shame, it is, umm - required. ;]

KuHL 951

Do you know what type of HG material it was? There are definitley traces of corrosion at the cylinder margins, the stud mount holes look fine. The fouled plug idea with buildup of fluids sounds interesting...didn't Laust P. have a similar theory on his milder damage to #4?

nine-44

Ahh yes, the CSI Rennlist unit is on the way, lol. Really, if we figure it out, it may benefit all of us in the future as these cars age. Possibly Hydrolocked at startup, cracked the piston weakening it. After warm up it poped and the rod took out the cyl wall? Or the second shooter on the grassy, eh, nevermind.

eman930

Holly crap, What happened, looks like some one drop some TNT in there. Anyway I have a good 85.5 944 full engine $950 plus shipping, I gotta pull the motor from the car

nine-44

fast924s, there is more than one guy on the board looking for a motor, if he doesn't want it, there seems to be a rash going here lately.,

eman930

Hey if some one wants it and can figure out how to ship it then PM me and we will talk

jonnybgood

I vote for this one. That an injector was sticking and number four plug wasn't firing (vibration? running on three?) so build up of raw gas until perhaps it ignited due to compression? Things weren't bouncing around in there too long or else the spark plug electrode would be trashed.

Dave951M

I seriously doubt hydrolock. If it was from water ingestion, there would be some indication of damage in the other cylinders. They seem to be pretty much ok. I have seen detonation at high rpm cause some funky looking disasters.