Dr. Dynamics

Hi everyone,

I was doing the serach but its a whole information overload
I found a scrap 88 944S and was wondering if it would be a good buy to get the engine (still needs a rebuild) or do a 16V head swap tp break the 350-400hp barrier.

Thanks

ramius665

Short answer: it is possible and you can break 350hp with less head work than an 8V head.

Long answer: Adapting a 16V head will require custom intake and exhaust manifold solutions and custom pistons to lower the compression and account for additional valves. Where most people seem to fall short is either the custom fabrication or the cost associated with paying someone else to build these parts for you. From an engine management perspective, the tuning aspect is much less of a concern than it was even five years ago. As of right now, you could order a DIYPNP microsquirt box or a VEMS setup and have the harness and ECU ready to go by the end of next week. There are still companies (SFR and/or LR) who will sell you exhaust manifolds and/or intake manifolds ready to bolt on but they come at a very significant cost. Wossner has the specifications to make custom pistons but with alusil-friendly coating will still come in above $1k. If you're interested in pistons, give Karl at Racer's Edge a call, he can guide you to a proper selection.

The real benefit to a 16V head is the flow rates compared to the 8V head. In rough numbers, it's almost a 2:1 ratio at similar lift numbers. The ability to time the camshafts will allow you to better tune the powerband and the presence of a hall sensor on the exhaust camshaft would allow sequential fuel injection down the road if you desired to do so.

But again, the largest constraint is cost. If you were to pay vendor(s) to make the necessary components you should budget about $5k in parts, not including the turbo-specific factory engine bits necessary to make a generally OEM appearing/functioning engine.

Is it worth it? You'll have to ask the folks running 16V turbo motors. There wouldn't be so many people pursuing this type of build if it didn't have tangible benefits. My motivation for building a 16V turbo motor was the ability to make good power with an engine under less stress than a similar 8V motor. As alwasy, YMMV though.

Dr. Dynamics

Great help!!

General comments...
-I am currently running MSNS Extra so check on that one
-Not in a hurry
-I've always done the car myself

So basically it would be left to speak to Tim @SFR to do a header and an intake? plus the pistons

Now is the block exactly the same? meaning I coud do the build using the purchased block on a stand while still using the car as it is?

blade7

Depends what that head would end up costing you for starters, it may make more financial sense to buy just an S2 engine to convert. You would have the better block too.

Raceboy

Exhaust manifold can be stock 16v one. But you need to make custom crossover pipe (as I did, twin-scroll one) and of course use better turbo, preferrably with twin-scroll turbine housing.

As for intake, I would suggest making it yourself or have it made. Why pay 1000+ dollars if you can make it for less than 500. Of course it requires you or someone to make CAD drawing of the intake flange, have it cut, fabricate runners, velocity stacks and plenum and then weld it all together but if you are familiar with machining it is no big deal.
I have done quite a few intakes over the years on different cars, I personally enjoy making them. Much more than fabricating exhaust

ramius665

There isn't really a vendor I could personally recommend. SFR is known for long lead times (measured in months, sometimes over a year) and a complete lack of communication. But they're also known for great TIG welding. I have an SFR intake and it was warped on the flange. Rather than send it back and wait for potentially months, I opted to have a local machine shop fix it.

As far as the block, the 944S shares the same 2.5L block as the rest of the 944 line in 87-88. If you're lucky, your driver side balance shaft housing was drilled for an oil feed to the turbo but then capped. My 944S (1987) is set up this way. Depending on the condition of the cylinders you may want to consider either Nikasil plating or sleeves.

As Raceboy can attest, there is significant power to be had out of the 16V 2.5L motors.

Dr. Dynamics

What cams would be advised? I beleive the cams are damaged. Thats why the car is left unfixed

ramius665

Ooof. Maybe a bit more description regarding the donor car is necessary to provide any further useful advice. If there is/was a mechanical failure of engine part(s) then it's highly likely this isn't going to be a good starting point for a future project. If you can't verify the engine currently runs then you're risking quite a bit of effort to possibly spend a lot of money and still not have a running engine.

To your question though, the S2 camshafts have milder cam profiles which make a less peaky powerband. I'm hoping Raceboy will chime in with his experiences of a 2.5L 16V turbo motor because I can't comment from personal experience. I have a 944S and it doesn't really come alive until 4k. With the S2 cams, it should have a bit more power before then.

V2Rocket

S/S2 intake cams are pretty close, S2 has milder exhaust cam...
In all likelihood the S2's "milder" manner is due to the increased engine capacity more than anything else.

ramius665

I'm going to pin the blame back on the camshafts. The 968 has the same displacement but radically different camshaft profiles and is peaky like the S motors. It only becomes tolerable because of the variocam.

Raceboy

I have s2 cams on my 2.5 16v turbo with S head. And it needed quite a bit of advancing the cams for the torque curve to move lower, otherwise it would really wake up at 5k. Probably could use even more advancing but for that I would need to skip a tooth and then adjust it back a bit from the adjustable sprocket.