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ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

They are. Same big end, same little end, same stroke, same length. All of the critical dimensions are the same as stock rods except that the big end has a different configuration on the shoulders such that it will clear the block with no machining necessary. Take a look here for a refresher. There is no reason that anyone NOT doing a stroker couldn't use these rods for a stock rebuild.
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erstwhile owner of just about every 924 variant ever made

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

So how are you increasing the stroke? Are you having a custom crank made?
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Yes, already made. Two of them. Rod journals were welded with more material then offset ground to add .25" to the stroke.

This was the design intent right from the beginning. We were given bad information (intentionally???) by a couple of well known 924 performance shops that told us we would not need custom rods to build a stroker. What they neglected to mention is that no custom rods means significant grinding on the block. Tom and I both discussed and decided that custom rods with a smaller shoulder profile (stronger & lighter) was preferable to removing material from the block, and possibly ruining it, since there's not much empirical information on where the water jackets are and such. It was the better alternative for both of us, and Crower assured us they could make a replacement rod that met our criteria. They delivered.
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erstwhile owner of just about every 924 variant ever made

leadfoot · Posted: Thu May 14, 2009 2:16 pm Post subject:

suprised you haven't had your block xray'd
S.
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

Rich H · Posted: Thu May 14, 2009 7:40 pm Post subject:

OK opinions then please:

I have just got notice that my main bearings have just turned up (Cheers Dan! I've just got to pay import tax on them now

) so I'm going to start on my engine build soon, I was going for N/A with a tweaked CR by skimming the block, but my spare crank needs grinding anyway as it's scratched.

So, instead of skimming the block and grinding the crank how about weld and regrind the crank offset by ~1mm: better CR (Aiming for ~10:1) and slightly (Just!) longer stroke, probably have it balanced too.

Worth the effort or not?

Idea is to go for a road engine with a wee bit more go.

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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Arvidw · Posted: Mon Oct 12, 2009 5:16 am Post subject:

Does the exhaust manifold of a 2.0 NA fit the 931cilinderhead?
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)

Rich H · Posted: Mon Oct 12, 2009 6:14 am Post subject:

No. Been there done that.

It's not with the effort to try and fit the turbo head. Buy a turbo instead - I promise it's better value!
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

Arvidw · Posted: Mon Oct 12, 2009 6:33 am Post subject:

Okey, thanks for the quick answer!
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl)