blade7

Are you implying iron is equal or superior to Alusil or Nikasil for a 944 cylinder surface?

951and944S

Of course, any piston can have coating applied.
The pre-send requirement for the Swain is to glass bead the piston to bare aluminum surface.

My top running engine in the Sp2 I show here in race vids is stock cast pistons coated with Swain PC9.

It's the last engine I will do with cast but all you have to do is use the factory clearance since it's the exact same piston still.

When you move to forged, you have to pay attention to any difference in piston/cylinder clearance recommended by the manufacturer, taking into account them film build thickness of the coating you use when fitting to final cylinder dimension.

What I would do additional to skirts, is have DLC or equivalent done to the ring groove area.
This lessens the stiction of the rings when transitioning between between upward and downward moments where they otherwise might not keep optimum ring seal with only ring tension to keep them expanded.
Ring mass can have an effect here and I don't see anyone talking about the SB Chevy piston rings being 25% more mass than the 944 stock rings @ 1.5mm v 2.0mm for the top ring and 1.2mm v 1.5mm for the #2 ring.
Gas porting the piston either vertically or radially and/or adding a machined semicircle void between the top two ring lands adds an insurance margin against ring flutter (less than optimum sealing, increased wear) which is a product of engine speed + stiction + ring mass - ring tension.
Adding ring tension is counter productive...

T

V2Rocket

I had thought that only wossner and mahle had an alusil compatible coating. Have heard of swain And others over the years but no success stories in 944 or 928.

interesting...

Jay Wellwood

How did you read that into my response?

Merely shared real world experience that we've both read posted by Shawn.

blade7

You seemed to be endorsing the hybrid stroker iron liners. Which cylinder finish/material would you prefer?

Humboldtgrin

Jay Wellwood

What I'd prefer is to better duplicate the experience documented. My apologies for reviving your old thread that I thought may prove beneficial for information regarding recent sleeving experience.

blade7

No apology necessary. If the plated ali liners than Penguinracer mentioned work, I learned something new. I'm still interested what your preferred cylinder material is though?

951and944S

Just a follow up because I mentioned but didn't have full info at home.

PoyDyn (Polymer Dynamics) is the piston skirt coating company that CP/Carillo recommends for their forged piston to be compatible in Nik/Alusil.

In Houston.

http://www.polydyn.com/pistons

T

V2Rocket

Any leads on alusil type rings that would fit a generic piston?

Carl Fausett

Two things:

Arias has been sold to CP Carillo. We used to get all our piston forgings from Arias, but they are Carillo forgings now. That is an improvement. We were surprised to find that some metric pistons sizes were no longer available to us after the switch. We use Wiseco pistons now and are happier than we were with the Arias ones. Coatings for Alusil (usually none) and Nikasil are different.

Same with pistons rings. Because the Nikasil has a harder surface, the piston rings for it need to be softer and are usually a form of cast iron. Alusil, although tough, is easily scratched and relatively "soft". Because of this, rings for Alusil are harder, and often chromed. Order your rings when you order your pistons, from the same supplier and at the same time. That's the best way to get it right IMO..

951and944S

Total Seal

Ductile-moly top ring, cast second ring, and a chrome faced 3 piece oil control ring.

By "generic" if you mean @ 100mm bore, part number for above at EBS Racing Don Weaver (don@ebsracing.com) should be -

steven74

I can second PolyDyn. I used to help on some dirt track sprint cars that always used PolyDyn for over 20 years and they know their stuff. Many positive reviews from area engine builders too. I live about 20 minutes from them and can assist with any local Houston work.

V2Rocket

was wondering if TS or anybody made a alusil type ring set (is it barrel shape? or something like that) in "Regular size" like 4"/101.6.
if there's an easy way to buy an off the shelf SBC piston and ring set, coat it and stick it in alusil barrels.