Thread: A new car!
View Single Post
Unread 07-18-2018, 02:17 AM   #162
GlenL
Workin' on it
 
GlenL's Avatar
 
Join Date: Apr 2009
Location: Minneapolis
Posts: 941
Thanks: 91
Thanked 85 Times in 77 Posts
GlenL will become famous soon enoughGlenL will become famous soon enough
Garage
Default Working out rings

As mentioned previously, I got 8 sets of Goetze rings and they all had gaps that were too big. The spec in 0.4mm max and the smallest was 0.66mm with the biggest being 0.813.

All of the pistons were Tolerance Group 1. I put one ring into all of the bores and found only two sizes of 0.711mm and 0.762. I was only using single blades of the feeler gauge so that leads to "two sizes" but they were all pretty close. So, no real opportunity to move the Goetze rings around to address the gap problem.

So, what to do? There aren't a lot of rings offered in 97mm or close to it. There are oversized rings for other engines that are near 97mm and 1.5mm thick but pickings are slim.

What I settled on trying were Mahle rings for the 911 Turbo (3.8l). These are 97mm and 1.5mm for a Nikasil-coated bore. It's hard to find good technical data but the Goetze catalog says that the same ring is used for both the 928 97mm set and the 911 Turbo set. Only the top ring is usable in the 928 engine.

I ordered 1 set of the Mahle rings to check out. The one top ring showed a gap on 0.533mm. Still not in spec but smaller than any of the Goetze rings. Gambling, I ordered 7 more. Surprisingly, the 0.533 ring was the largest and the rest measured 0.431 to 0.483mm. This is in a bigger hole. (#1)

The numbers for the rings is below along with the Plastigage results for the mains.
Attached Images
File Type: jpg RingGapsAndMains.jpg (227.5 KB, 1 views)
__________________
1980 928S Euro x2
1987 944 N/A
GlenL is offline   Reply With Quote