924Board.org

johnwalklett · Joined: 17 Nov 2003 Posts: 31 Location: staffs england

H Guys,

you may or may not remember but I had a problem with my 931 smoking badly all of a sudden. I have finally traced the cause of my problem. After doing a compresion test i found No.3 was down to 50psi, hoping this would be the head gasket I removed the head to find no such problem. So I continued stripping and found that the piston ring islands had broken on No.3 piston.

My question to you all now is where can i get a set of replacement pistions and rings from. The pistons in my car are STD I and the bore size is now 86.53mm after I honed the bores out. So I will be okay replaceing them with STD I again.

Regards

John Walklett

cooper931 · Joined: 13 Nov 2003 Posts: 32 Location: Fayetteville NC

http://www.ebsracing.com/water.html They sell a set for 650 dollars fairly pricey but a decent set.

Paul · Posted: Thu Nov 27, 2003 11:41 pm Post subject:

Yep, EBS is a great source, order the other stuff you need from them and bargain with them to lower the price.

Kurt Ramsden · Joined: 27 Oct 2003 Posts: 6 Location: Middlesbrough UK

John,

You might also wish to try http://www.9mracing.co.uk/html/

They are Warrington based so not far from you. The website shows mainly 911 stuff but I understand they are good for front engined cars as well.

Good Luck

Kurt

Joes924Racer · Posted: Sat Nov 29, 2003 1:20 pm Post subject:

you cant find a std single piston rollen around over there..
for rings theres a few places. I have a single std piston.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

johnwalklett · Joined: 17 Nov 2003 Posts: 31 Location: staffs england

I contacted 9mracing yesterday and they were very helpful. They seem to be struggling a bit. But they haven't given up yet, I have to phone them Monday. I am a little reluctant to replace just one piston, If one has broken how much longer will the other last?. I have been told that this is a common cause of piston failure(is this true) and I don't really want to strip the engine again in 3 months time.

Worst case I will probable get some JE pistone from EBSracing.

Regards

John

numbbers · Posted: Sun Nov 30, 2003 11:15 am Post subject:

I have never heard of another case of a broken ring gland in a 931. Anybody else? I would try to find out why the piston failed, and check your cylinder bore very carefully for damage before you purchase a new set of pistons.
_________________
1980 924 Turbo

Joes924Racer · Posted: Sun Nov 30, 2003 2:18 pm Post subject:

Ooops these are stnd 924 na pistons. Let the search continue.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Paul · Posted: Sun Nov 30, 2003 11:48 pm Post subject:

Sometimes the following happens:

A ring breaks

Owner notices low compression

Owner trys to remove piston without removing the ridge at the top of the cylinder (too poor to buy ridge reamer)

Broken ring jams against ridge, owner swings rubber mallet harder

Piston ring land breaks.

In this case it was me in 1971.....

johnwalklett · Joined: 17 Nov 2003 Posts: 31 Location: staffs england

In my case I suspect it was due to the fact that the car had stood for 9 months before I brought it. I think the rings had siezed in the piston. When I removed the offending piston the 1st and 2nd ring were stuck to the ring land that had broken off the piston. Luckly I only did about 4 miles with the piston broken and the bores and okay.

John

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

With the block being honed out, that may have contributed to the breakage, in that there is "extra" room in there for the standard size piston to rattle around. A bore of 86.53 is the largest bore in the "standard" bore. According to the manuals, each bore size has it's own piston size.

_________________
'79 Eurospec 931

numbbers · Posted: Tue Dec 02, 2003 10:56 am Post subject:

If the rings had siezed in the bore as you indicated, I would consider going oversize on the pistons, and having the block bored to match. I can't imagine that the rings could have siezed (rusted) to the cylinder walls, and not damaged them.
_________________
1980 924 Turbo

Kenodog · Joined: 25 Jun 2003 Posts: 2669 Location: Vancouver,B.C.

I have a set of 86.75 out of an 80 931 if you're interested.I would be asking $200.They would be clean and shotpeened on the undersides.Rings are included and they are good too.Let me know.
_________________
1979 Euro 931, Olive
1981 931, Sabine
1991 Ford Ranger XLT 4x4, Ricky
1996 Ford E-350 ex-FedEx Van
2014 Mazda CX-5 (Kinderwagon)
2019 KTM 790 Adventure
2024 KLX300
2024 KLX140

johnwalklett · Joined: 17 Nov 2003 Posts: 31 Location: staffs england

just to clear up a few things.

The rings had siezed in the piston groove not the bore and after removing the pistons I have honed the bores until they where all cleaned up resulting in a bore size of 86.53mm.

Kenodog..may be interseted in your pistons, can I still get new rings for that size piston? Would you be prepared to post them to the UK? I think the postage is about $85.

John