WallyP

If you plan to install new ones, no real reason to check them for wear. We have had some folks who want to spend as little as possible to get it running again. You need to get the piston grooves clean without scarring or scratching the sides of the lands at all, as those are the sealing surfaces.

928 at last

Wally can give you the specifics, but it isn't the rings you're checking.....it's really the bores. The end gap will tell you what size rings you need to go with.....

gbgastowers

I already bought 97mm rings from Pelican. I didn't know I had a selection to choose from. I will try and measure but hopefully the 97mm are what it needs.

gbgastowers

222222

Roy928tt

Ah, so it was rings stuck in the piston grooves, that will do it every time.

From what you say, the old rings are not that worn at all.

Cheers Roy

yardpro

can he not run a "scatterball" cylinder hone through the cylinder to clean it up...
We used these things on nikasiil coated aluminum cylinders on race bikes (dirt) all the time.. you have to be very careful, and only do one or two passes, but it restores the oil grabbing cross hatch, and created a great ring seal.

Hilton

No.. the 928 is Alusil, not Nikasil (pistons in a 928 are coated, not the cylinders as is the case with nikasil).

Honing a 928 engine will result in poor compression, blowby, and a poor engine. There should be no cross-hatch marks at all - it should be smooth.

After correct alusil "honing" (more like buffing with a special paste), the surface exposes the silicone at the microscopic level. GBA's bores look ok at first glance.

gbgastowers

I can't get them out. I am using my other pistons with new rings. I have to at least get the rings out of 1 because 1 of my extra pistons is damaged. Soaking one in ATF at the moment and only have 2 bores to go. Gunar

928 at last

To do a search here on the best penetrating oil.......
ATF by itself isn't going to do it (Most likely).
The idea is to soften and or dissolve the carbon that's gummed things up.
(Stuck the rings in compressed mode)

namasgt

Have you looked in to buying some berry man degreaser from Car Quest?
If your rings are stuck due to the carbon turning into sticky stuff, it will dissolve it and you can take your ring out and use the same pistons. I have used it to clean 928 pistons with no problems.

gbgastowers

I think I can get the rings out of one of the pistons and use it as my final one(#7). It's soaking in a mix of everything tonight. I am about done with the major surgery and I can start closing it up tomorrow. It feels good to take care of this major problem. I have made a really big mess so I'll post some pictures of it.

Landseer

Good use of the W-S Journal.

I see you have a nice mat to curl up on by the garage door. BTDT.

Rob Edwards

The best piston degunker I found is Berryman's Chem Dip. Don't get it on you...

BC

I LOVE that stuff. Cleans pistons just by sitting in it. Cleaning the berryman's off - "One glove, one piston, one glove, one piston" - immediately starts to weaken the latex and nitrile gloves. But it WORKS!

namasgt

^^^^ that's what I have suggested, powerful stuff, stinks too so you want to do the cleaning in open air, not inside the garage. I think if he uses it he can just reuse the original pistons and put them in to their original bores, since their worn together.