cpt_koolbeenz

Does anyone know the stock ring material and coating for our cars? I am looking for aftermarket rings for use with our alusil blocks... I would use stock rings, but my bore size is 101mm. I crossposted from the normal 944 board since I think most people on the turbo forum mean business... (Not that the regular 944 board is bad... but I'm sort of biased.)

Thanks,
Chris

m42racer

I,m sure the stock Ring material is Ductile Iron, but I,m not sure if the Top Ring is a Moly faced ring as well. You can use either a Ductile Iron plain ring or better would be a Moly faced Ductile Ring. DO NOT use a TOOL STEEL or CHROME FACED RING. Although these rings are better suited to Turbocharging, they should never be used with Alusil coatings. The problem may be finding the ring width you need in that bore size.

Ski

Chris, your not going to use the ones that came with your pistons? We just pulled the head on the track car to do a check on the block and the cylinder bores were perfect.

cpt_koolbeenz

Thanks m42...

Bret-
The rings are crap... they do not fit the pistons properly. The rings are a 3.953" ring with a .020" oversize. That brings the final size to a 3.973". A 101 bore, as mine is, is 3.976" or a 3.978" file fit... Why a 3.973" ring came with 3.976" pistons is beyond me! I am a little annoyed because my ring gaps are .025" <- thats pretty huge! Porsche's wear limit is .030"... I am already there! I talked to Tom, he said everything fits... he has had no problems with the kits... Well, if nobody checked their end gap specs, then there would be no problems... I don't know if you have big gaps with the 100.5's, but mine are unacceptable (have you measured your gaps?). So, there goes another $130 for a new set of rings... No chance in selling the old ones, because they don't fit ANYTHING!

I bet your rings are 3.953" and your bore is around 3.956" and you have almost the exact same ring gap as I do (.025").

Ski

The ring gap was .012 according to Duffin Machine in San Antonio, or that's what they reported to us on the track car. Maybe Tom can call and intervene with his vendor and get you a new set, worth a call again, the vendor can certianly do a closer tolerance the next time I would think.

m42racer

I would be more worried about a 0.012" gap than 0.025" on a Turbo engine. Rings lose tension and close the gap normally. Your problem may be the back clearance. 3.976" is a size made, but in what widths I'm not sure. They must be available if the Pistons were made.

fast951

Chris, You might want to get in touch with MySwiss. He had similar problems but finally sorted it out.. I think the issue was with the piston size not the ring, but I don't have the complete story.

cpt_koolbeenz

I told my builder to get the 3.953" rings in a .030 oversize. That would give me 3.983" ring and my builder is going to file fit them to a .016 gap size. That should work... They do make a 3.976" ring, but the ring widths do not match my pistons... The pistons have 1.5 1.75 and 3.5 ring widths IIRC.

The pistons, in my mind, should have been made just .024" larger to be a 4" piston... There are unlimited options for 4" pistons! Oh well... it is a learning experience. I will do things differently next time!

Thanks John - I will talk to MySwiss - I think he also had the 101mm pisons.

cpt_koolbeenz

m42-
Do you think the second ring is cast iron? The only sets with duct iron top rings have cast second rings... I assume cast iron rings will still work with our blocks?

Thanks,

macnewma

You might want to ask a Porsche engine builder what they recommend. Try Neil at Performance Developments or try contacting Memphis Motorworks.

Max

APKhaos

So, what the deal about re-ringing the Alusil block without honing the bores?

- I've heard several 'knowledgeable' sources say that Alusil bores should not be re-ringed without honing.
- David at Lindsay tells me that I can re-ring provided the bore is in good shape [dimension & wall condition].

My 34K mile race engine comes out tomorrow for head gasket, rod bearings, and general freshening. If the bores are clean and wear is in spec [should be at 34K] then I'd like to install fresh rings. So, this is the last burning question right now.

pk951

Piston ring gaps in shop manaul grove1 -0.20- 0.40 0.80
grove2 -0.20- 0.40 0.80
grove 3 -0.30- 0.60 1.20

Volume 6-turbo

m42racer

The second ring will almost always be a Cast Ring. It can be as the forces are typically less. It is often a torsional twist type, or even a reverse twist type. No problem. As for re ringing an Alusil Block without honing, no problem as long as the cross hatch is still evident. Polished bores should have the cross hatch put back. Simple procedure about 30 secs per bore. This should not be confused with honing the bores to bring back the surface after resizing. The cross hatch effect is all normal stuff. Trying to promote the hills and valleys in the surface to help the rings to bed in.

APKhaos

Thanks M42 - let the re-ring begin!

cpt_koolbeenz

"I told my builder to get the 3.953" rings in a .030 oversize. That would give me 3.983" ring and my builder is going to file fit them to a .016 gap size. That should work... "

Well, I went this route with a Hastings/Perfect Circle/Equiv. duct. iron top ring and cast second ring... My builder called me tonight telling me the engine is together and everything fits perfectly... Phew! Only four extra days and $130 out and I (with the board's help) remedied a certain person's (he shall remain nameless) FUBAR. That person kept assuring me "everything fits" with MY kits... That seems to be true except if your name is cpt_koolbeenz or MySwiss and you order 101mm pistons from incompetent "tuners." Sorry for my ranting... Long day - little sick of engine problems!

Thanks guys!