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[Mike9311]

The biggest issue when looking for alternative pistons for these cars is the wrist pin diameter and compression height.

There are a ton of 86.5 to 88mm pistons out there especially from modern cars but they have really low compression heights and look more like F1 pancake pistons compared to our soup cans. This is also why Dan's looked cool. He either stroked or long rodded his creations (or both with his DProd). This lowered his compression height and therefore overall piston height.

Dan looked and researched like crazy and I have been doing it too as of late since I need a custom config. Our wrist pin size is rare as well as the Compression Height (Center of wrist pin to top of piston). This is why going with a longer manley rod (or other brand of which there are tons as well) is so enticing. Yes, you are forced to grind down the crank rod journals (also allows you to stroke if you want) but you get to use a smaller, more available wrist pin size and other pistons do become available as a choice because the compression height is smaller/shorter. They are not perfect but they become a option.

CarreraRSR those pistons are interesting because the Wrist Pin is smaller at .866" (22mm) vs stock .944" (roughly 24mm). You would need to bush the rod end with Alu-Bronze or similar which is totally doable. Saves some weight in the end

Gegge might chime in, I hope, since I know he has researched this topic to death as well over the years. He always has some interesting take of things
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[lildude4life]

I got my JE's via topend performance in CA. Went with 22mm wrist pin's and new pauter rods so I didn't have to deal with the odd wrist pin size. Also could then use standard ARP rod bolts as I know those are hard to find as well.

Only thing I wished I did first was have my machinist verify everything as I think I ended up with a bit more CR than I wanted as the deck height seemed off for some reason once everything was put together.
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"931 EFR" 81 931 S2 w/ EFR 6258 turbo, EFI, Haltech Elite ECU, 240whp

[safe]

wrist pin size isn't a big issue, you can have the rods rebushed to 22mm.
Compression height is a bigger thing. But there was BMW rods that was a bit longer, it "only" needed some sort of spacers to center them.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[Mike9311]

[hayeslewis]

Well I'm having a hard time getting pistons made due to all the delays so I'm looking at off the shelf options. I have some light weight rods that are actually bushed for 22mm pins, so the VW pistons are a option-but that will make for a perfectly cylindrical combustion chamber with an NA head. That cant' be good-or can it? Some other crazy ass ideas I have include pistons from the 2.2L K car and from the same folks in Detroit-yeah you're not going to believe this. Pistons for a slant-6

https://www.summitracing.com/parts/uem-skb268-1-0mm/make/chrysler

https://www.summitracing.com/parts/slp-244np30/make/dodge

Of course these are more starting points, the slant 6 piston is a flat top that would make for a 30:1 CR! But I've seen dished pistons for this engine...
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Hayes Lewis
1979 924 HP
1979 924 ITB/HP???
2007 Armada
2013 Hyundai Elantra
1972 MG Midget Vintage project
Unstable electrified three wheeled Bicycle truck

[anthonimartini]

hayeslewis, there is a shop here in portland oregon called Bearing services that i have had custom pistons made before. they get them made from a company called traum. it was about 1500 bucks for a old bmw E9 straight 6 so id imagine it would be at least a bit less for our 4 cylinders. he would probably want your block to he could bore it correctly though. if you try calling them tell them anthoni from avant garde collection referred you.
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ive saved alot of 924's
current:
79 MochaSchwartz 931
83 944
87 924S
Instagram @anthoni.jpeg
formerly known as turbellion, lost password.

[n_l]