Bakanepa

I have a 1986 951 with oversize Wössner pistons and scratched bores, which needs some love.


I recently aquired a N/A 944S parts car with a block with beautiful bores which i intend to use. However, the 16v cylinder head on it has a broken tooth on both cams, so i can't sell it for much, but would like to use it on the 951 if it's possible without burning a buttload of money.


I already have a k27/8 laying around, so i'd need at least a new intake, headers, MAF kit.


My main question is about pistons. To remain in a sensible budget, i'd like to use my current pistons, i have both the stock S pistons, and some old stock turbo pistons. Can the N/A one be machined to a lower C/R with a thicker headgasket and still hold turbo power? Can turbo pistons be machined to fit a 16v head? The ones i have are tolerance group 1, while the block is a 2, so i'd probably need other ones. Would like to stay in a $2k budget, or should i forget the idea immediately

Raceboy

Both can be done (flycutting turbo pistons and machining 944S pistons), I use stock 944S pistons that I machined down 1mm and it has held up just fine for over two summers at 450-500 hp depending on boost pressure.

odonnell

Sell the Wossners to fund an external-drive DOHC setup.

Raceboy

Agree, if you already have ruined cams then external drive would be my choice too. And it can be nudget too, V2 Rocket came up with some good solutions.

V2Rocket

You can get the teeth repaired on the cams for like $500/pair at WebCam...I just had a pair of 944S cams worked on there a few weeks ago (different work though).

Or, I have a friend who has at least 1 good set of 944S camshafts laying around his shop who would sell them complete for a good price.

I'm with Raceboy - cut the stock "S" pistons like he did to drop the CR, maybe add the thick head gasket for a little more CR reduction (depending on the gas you can get and the tuning ability you have).

odonnell

The 16v is head is less prone to detonation, but cast pistons aren't going to take much. Going with an off the shelf tune is asking for trouble...after you pay for everything needed to adapt a 951 DME to do the job and get it tuned safely, you would end up spending near or more what it would cost to get a decent standalone. Raceboy and V2 can tell you all about VEMS, there are other options as well depending on what you're looking to get out of the build. $2k budget may get you home, but there is a lot of room for false economy here.

V2Rocket

944 NA/S/S2/968 pistons are hypereutectic-cast which is fine for a "mild boost" situation as long as the tune is good.

99% of OEM-produced boosted cars just use hyper pistons rather than forged because they can take the beating but fit the bore really well for sealing (emissions)...see Ford, GM, MB, BMW, etc.

Even the 951 pistons are "forged hypers" but certainly stronger simply due to the thickness of the crown.

Raceboy and his VEMS are "kick-***"

Bakanepa

I do like what i'm hearing. Unfortunately the Wössners aren't likely to be possible to sell, as i expect them to be destroyed. The dual cam gear setup sounds like a good idea, as when the tensioner failed, chain broke, broke the two teeth and ripped off the piece from the head where the tensioner attaches. Broke it on Nürburgring last week, welded it back and drove 3000km home, and as i pulled the valve cover i found a crack in it again.


Is there more information on V2's dual gear setup, found one thread with some info, but more detailed and the result would be awesome?! Any information on the dual gear setup is warmly welcome.


I don't know jack about engine management. My current setup is just a simple chip, AFM and DP wastegate 3" from the turbo and k26/6. If i was to go with VEMS for example, what parts will i need? What replaces the AFM? Approximate cost? I have some studying to do tonight on this.


My k27/8 is from a 964 turbo, I guess i have to combine it with a watercooled hot side from a late 944? What kind of power would be reasonable to expect from this setup?


It's not a disaster if i can't remain within 2k, but wouldn't like to double it.

333pg333

$2k to put together a 16v turbo motor??? I'll take 10 of them.

Paulyy

Yeah i don't think you'll get far with 2k.

Unless you're doing ALL your work. like ALL of it.
because you're going to need:
- buy or modify forge pistons.
- fix or get new cams.
- Can't remember if the 16v head has the same intake and exhaust flanges as the 8v. But if not, there's more modification and money spend.
- getting a computer to run it all. + tune.

+ extra for other stuff you haven't accounted for that will need replacing under maintenance.

refresh951

I agree except you do not need fix or get new cams. Now if your budget was $4.5K and you did all the work....

Paulyy

Broken tooth on the cams? I'm not sure a way around that. But then i haven't played with 16v engines.
4.5k sounds reasonable

refresh951

Oop, missed the broken teeth 5K

Voith

Exhaust is 3 bolt pattern instead of 2 and intake ports are oval not round, so double trouble.

Raceboy

With japanese cam and crank sprockets he can make external drive and leave the cams as-is. He can just buy longer timing belt and that's it. Even I had to buy Volvo 2.4 diesel timing belt due to the early NA block and manual tensioner+16v head combo. No big deal.

Regarding the pistons, people tend to forget or ignore cold hard fcats that I have ran for two summers with milled 944S pistons and 1.2-1.5 bar of boost on 16v head, depending if the road is wet or not and the motor doesn't seem to mind. If you have poor tune you can through whatever parts in it and it still fails.

Also Kristo's (Jõujaam) mint green 968 turbo had S2 pistons in it, was just fine at 680hp.