924Board.org

numbbers · Posted: Tue Sep 30, 2003 9:12 am Post subject:

NAPA sells the tensioners cheap, and they are the old style, so you can still use a wrench to adjust the tension. Don't mess with a three point valve job, it will cost you more, and won't add anything for a street engine. If you don't need valve guides, you could just buy the new valves, and lap them in yourself. A lapping tool is very cheap. However, when you bend a valve, you usually damage the guide. I would just take the head to a good machine shop, and have them check it out and tell you what you need.

Guy's how expensive are the valves for these engines?
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1980 924 Turbo

Lizard · Posted: Tue Sep 30, 2003 9:30 am Post subject:

the parts bin has the exhaust for $52.37

I am not sure about the intake valve, but the intakes are normally a hair cheaper,
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3 928s,

jl924t · Joined: 03 Nov 2002 Posts: 214 Location: Surrey, BC Canada

In March 2001 I bought intake(93110540102) & exhaust(93110540602) valves for $125.00 CDN each. Eurasia Auto in Edmonton Alta. Premium prices but I was glad to find them.

Paul · Posted: Tue Sep 30, 2003 9:49 am Post subject:

Porsche 931 exhaust valves are sodium filled....

924 turbo · Posted: Tue Sep 30, 2003 10:41 am Post subject:

Sorry to hear of your misfortune, CMXXXI. The tensioner should be replaced at every belt change. This information should be in the FAQ, as it is vitally important for the turbo model cars.
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Jon Furst

Joes924Racer · Posted: Tue Sep 30, 2003 12:53 pm Post subject:

Awww darn cmxxxi , Ive broke 2 tensioner pulleys and one belt
and yeas the belts do whine loudly if on to tight like a supercharger
the trannies working real nice though from the sounds of it.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Alex Roy · Posted: Thu Oct 02, 2003 4:01 am Post subject:

This is a good reason to pull off the road and inspect the engine ANY time you hear or feel anything abnormal. If you hadn't tried to limp home, you would've saved your self a lot of money.....but I'm sure you already knew that

I'm sorry to hear your misfortune.

I'd start with taking your cam out, if you have bent valves, the valve ends won't stick up as high as the good valves, if you have broken off valves, they will stick up higher than the good valves.

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

It happens every time...that one last bolt won't budge. Or as is the case today, the bolt holding the passenger side engine mount just spins and spins. I can hear the spring inside the mount as I turn the nut. Damn, and I was so close to pulling the motor today. I'm going to have to pull out my trusty Dremmel tool in the morning and cut the nut off.

Got all the "stuff" removed and the transmission & torque tube pulled back, all I lack is the engine mounts...

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'79 Eurospec 931

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

don't pull out the dremmel just yet! i believe you can fit a 17 or 19mm wrench between the bottom of the motor mount and the top of the frame that it mounts to. the "stud" that goes through the mount has a head to fit a wrench on so it doesn't spin in the rubber. you might need a pretty thin wrench to fit it in there if i remember right.

congratulations on the exhaust bolts! i had to cut off a couple.

-nick

Lizard · Posted: Mon Oct 06, 2003 2:37 am Post subject:

Instead of undoing the motor mount bottom bolt, undo the 2 on the top, then undo the 3 hex key bolts holding the motor mount arm to the block, this might be tricky unless you have removed the exaust manifold off the head,
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3 928s,

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

Update... Got the motor pulled, yippie!

Instead of cutting off the lower bolt on the motor mount, I managed to remove the top two, bend the heat shield out of the way and yank the motor. As I suspected, the motor mount is shot (see the broken spring?)

But now I can't get the bellhousing off, boo-hiss! I don't want to strip the motor until I can get it mounted on a secure stand, but I can't get the clutch release lever shaft out. A good thing I wasn't trying to do all this with the engine in the car!!

At any rate, I could use some suggestions as to how to remove the shaft. The factory manual (and Haynes) says to screw in an 8mm bolt and remove it - right, easier said than done. I've posted another thread in the General Discussion section on this( http://www.924board.org/viewtopic.php?p=68290 )asking for help, as removing a stuck piece like this isn't unique to the 931. Read the post for my last-ditch idea. Any and all suggestions are welcome.

Oh BTW, I did pull the valve cover and I can see that at least the #1 exhaust valve is bent. The cam follower has a big dent in it, something like this

and it isn't in contact with the cam. The good news is that the cam doesn't have any flat lobes like Augiedog found. Thank goodness for that.
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'79 Eurospec 931

Paul · Posted: Tue Oct 07, 2003 9:07 am Post subject:

I use a slide hammer to remove the bolt, or you can use a long punch and drive it out from the other side.

Make sure you have removed the lock bolt...

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

Here's the latest of the gorey details about what happens when the timing belt breaks on a 931 engine...

I pulled off the head Sunday and found three bent valves, the exhaust on cylinders 1 & 3, and the intake on #2, plus one cam follower is badly dented and will have to be replaced. I've located a rebuilt head so I'm buying it as a direct swap-out, and then will see about repairing this damage myself. I supsect I'll need some machine shop help, but I should be able to do most everything by myself, or with borrowed equipment.

The complete photo album (selected photos) for the weekend's strip-down can be accessed by clicking the first photo, or if you aren't that interested, click the other photos for larger images of the damage to the valves and pistons.

..-..

The last photo shows damage to the # 3 cylinder piston crown/dish that occured the LAST time this happened. A valve head broke off in this cylinder, and things were repaired while I was still in Germany by a local mechanic. I didn't know it had caused this sort of damage.
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'79 Eurospec 931

Lizard · Posted: Tue Oct 21, 2003 4:10 am Post subject:

well it doesn't look too bad, only 3 bent, I dont know if the pistons are reusable tough,
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3 928s,

CMXXXI · Joined: 05 Nov 2002 Posts: 1939 Location: Vicksburg, MS

The "last time" this happened, in addition to the broken one I also had two others that were bent. None of the pistons were replaced that go-round, so I'm going to bet/gamble that things are OK. I would have guessed that if I'd had any problems, it would have been with the #3, with the huge gouges on top.

It's interesting to see though, that the gouges seem to affect the flow through the combustion chamber. The carbon deposits definatly show a differnt pattern than the others. When I clean things up, should I grind down the ridges to help smooth out the flow pattern? I can't imagine that grinding off <=1 gram will cause any imbalance issue.
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'79 Eurospec 931