78mm crank in S2 engine what’s new compression ratio

[944m3]

Yup, I have a running ‘87 951.

[blade7]

People have skimmed the S2 pistons, and it can work that way. I know someone that used a standard 968 bottom end, and forged Porsche rods, and that worked too. You would be limiting the amount of boost you could run though.

[Bergerac]

That’s what I’m working out in my head, what can I afford to do right. That being said, I do take inspiration from Peep and others I’ve read posts from. You can do a lot with just stock parts. Won’t win Le Mans but will work just fine for your grocery run and occasional track day.

At the end of the day, it’s just a hobby though, so I’m willing to make a mistake or two.

The other thought that has crossed my mind was selling the S2 engine and just going with a 944S 16v head that bolts on to a 2.5 block. (Yes I know I will still need custom intake and crossover). I can keep the internals I have now, just flycut the pistons for valve clearance, maybe upgrade rods with lighter Molnar rods.

If anyone has one laying around, let me know. I might be interested.

I'd be careful with the 2.5L 16V heads, the early ones had a casting fault and were prone to cracking from what I've read.

[michaelmount123]

Either the S or S2 cylinder head can be used on a 2.5, but the S2 would need a water passage modification. I've done lots of these. However, I've gotta think the turbocharged S2 engine will make the biggest smile for the buck. Yes, would need rods, pistons, intake, and several 951 components to complete the build.
Suggest you chat with those that have done it. Tom, Thom, others.

PS: Yes, the S heads are prone to cracking at the head stud boss. Would suck to encounter this once it's all together. The heads will pressure test okay, but leak once the head is torqued on the block. BTDT.

[stitch2k1]

@OP
I have a rebuilt 2.7 head I would be down to trade straight across for your S2 head.

[944m3]

Appreciate the offer, but I think the mythical 16v turbo is my goal.

[stitch2k1]

Appreciate the offer, but I think the mythical 16v turbo is my goal.

It's a lot cheaper to run an 8v. Unless you're shooting for 600hp there is no real gain by 16v from what I have researched.
If you change your mind let me know, I could always use more S2 parts.