951Doc

The Goetze rings on my freshly honed 100mm cylinders gap as follows

Center rings: 0.457 to 0.508 mm
Top rings: 0.356 to 0.381 mm
Bottom Ring 0.178 mm (one measurement only)

Porsche specs show tolerances for the center and top ring gaps of 0.20 to 0.40mm, and the oil scraper (bottom) ring 0.30 to 0.60mm.

I'm clearly out of tolerance on the center ring, and barely within on the top compression ring. My conscience says ditch it, go with the Lindsey Racing rings, or become the neighborhood mosquito fogger using the Goetze rings.

Has anybody else run Goetze rings this loose and lived to write about it?

951Doc

Oddjob

I dont remember the exact numbers offhand, but I had a similar gap spec problem with the 2nd comp. ring (Goetze ring set).

There is a factory tolerance for new (setting the gap between 0.20-0.40mm) and there is a wear tolerance. I think the wear tolerance is up around 0.80mm. So I used them.

I do not think the larger gap is uncommon w/ the Goetze 951 rings, and most do not have any complaints about compression or sealing.

EDIT - missed the honing comment. Start with answering Ski's question.

Ski

describe freshly honed?

951Doc

The block underwent O-ringing, deck surfacing, ARP stud replacement etc, and the cylinders were lightly honed and burnished (ref: Porsche Workshop Manual 944 Vol 1 13-53-13-55). The machinist is very experienced in Porsche Alusil, and does work for JME, so I trust the work completely.

The block had about 90K miles on it, with no scoring and true throughout the bore, so material was not machined out. I Rechecked bore diameters, at 60mm from the top deck surface, all cylinders were 100.00 to 100.01 mm. I was surprised to see gaps that large for cylinders that weren't bored out. More surprisingly, the oil scraper rings, which are allowed to have looser tolerances, ended up having the smallest gap.

951Doc

Tom M'Guinn

I've never tried them, but I note that Pelican sells "Deves" rings, which seem to have a good reputation in other cars. Or, I wonder if a different batch of those rings would yield different gaps?

Tedro951

This is one of those areas where I wouldn't take a chance, regardless of others experience about the loose rings. Its frustrating waiting (and paying for) new parts, when the torque wrench is ready and you've got free time, but snuff like this will run through your mind every time you start the car.