mahle rings 930

[81Kremer930]

We are in the process of rebuilding a 81 911 turbo car. Upon the breakdown, the vehicle had 2 broken rings, but everything else internally looks good. The case is split, the crank will be polished, bearings replaced(all). I have read that when the rings break, the pistons, cylinders, and rings all need to be replaced. The cylinders look great, as do the pistons. The car has been sitting for awhile now, don't know how long, but with cobwebs on the brake calipers/wheels, etc, I'd say for sometime. If so, which rings to use.... The only way I can find the Mahle rings is from the dealer(expensive as hell).... or can the Goetze rings be used?(these can be found a lot of places, and are much more friendly economically)

[spuggy]

Rings can break from detonation; 930 rings are hard - and thus brittle.

This is the car with the dial'o'death and the boost gauge that shows 1.2 bar on the tell-tale? Uh, right...

[81Kremer930]

That's correct about the boost gauge.... From what I have gathered that's way too much boost for a stock motor. The car has sat for some time as well... Could be detonation, bad gas, too much boost, etc. Luckily everything else looks good! I was curious to know if the cast replacement rings would be alright to use... or should I look into replacing them with the chrome/steel Mahle rings?

[JFairman]

I think you should ask this question on the engine rebuilding forum. There's alot more good experienced knowledge on subjects like this over there.

I thought Goetze rings were origonal in air cooled 911 motors. I know Mahle makes pistons and cylinders but never heard they make piston rings.

[WERK I]

One thing often overlooked during rebuild is piston ring side clearance. If the side clearance is out of tolerance, you are throwing good money after bad. It is just a matter time before the rings break again if there is excessive side clearance.
Here's the specs;

Top compression ring: 0.070 - 0.102mm(new) 0.2mm (wear limit)

Second comp ring: 0.040 - 0.072mm(new) 0.2mm(wear limit)

Oil scraper ring: 0.020 - 0.052mm(new) 0.1mm(wear limit)

[vas930]

Originally Posted by JFairman

I think you should ask this question on the engine rebuilding forum. There's alot more good experienced knowledge on subjects like this over there.

I thought Goetze rings were origonal in air cooled 911 motors. I know Mahle makes pistons and cylinders but never heard they make piston rings.

MAHLE Group | Piston rings

[Tippy]

TotalSeal made my rings for $250