Goetze ring gaps

boosted79 · 05-07-2016, 05:42 AM

I'm rebuilding a '79 930 for street use, normal upgrades with SC cams, headers, turbo, big IC, stock boost .8 bar. The Goetze ring gaps, esp. the oil ring are coming in above or way above stock spec. In some cases they are only a few thou tighter than the 80k mile ones that came out. The oil rings in a cylinder that is exactly at std. spec are at .018" vs. spec. of .006-.012" Compression rings are at .013-.016". I don't want to install new rings that are starting out only slightly tighter than the old ones. What do you guys recommend? Hastings, OEM, Total Seal? Does anyone make file-to-fit rings for these engines like ones available for an iron block? Actually I'd be happy with these gaps in an iron bore but not in aluminum jug. I'm sure these will be "OK" but I don't want just OK. .006 is awful tight though on tight end of spec. I would probably go with 10,12,12 thou. top to bottom.

racing97 · 05-07-2016, 03:52 PM

Unfortunately all their specs are for Cast Iron blocks you can't go wrong with .010 or even .008 on the top but they make what they make and in Hastings which is the bulk of aftermarket rings that Piston makers supply, they will have to give you a larger ring to bring the gap in then you are going top have to grind it. Try always to buy Factory Rings right from the Dealer and make sure your Pistons are cut for standard grooves. Specify the Stock dimension if you are have pistons built, by the way the ones they gave you will work and not as bad as your think if you are not trying to get 100,000 out of the rebuild.

Regards

boosted79 · 05-08-2016, 05:58 AM

Thanks, I'm going to call hastings and see what they say their gaps will come in at, maybe buy one set and measure the gaps. I have no problem hand-fitting each ring to get it right. I just can't see installing new rings that are already worn vs. the Porsche specs. Will I feel the difference in the seat of the pants dyno, probably not, but it will def. show up on a leakdown. The side clearance is perfect, this is on the 80k mile pistons.

Mark Henry · 05-08-2016, 07:44 AM

You should be OK,
Ideally yes you would want a tighter spec, but I doubt it would cause issues.
.006 is fine on an aluminum cylinder.

If you go with a hastings set be sure they are OK on nikasil, as they do not like the spring loads of the iron cylinder rings.

BURN-BROS · 05-09-2016, 07:35 AM

Be careful when gapping the aftermarket rings, Most are not the same material as the ductile iron Goetze. Personally I do not go any closer than .012 on the top ring with Nikasil.