johntorg

It looks as if it was a bit of a false alarm. After looking at the tensioner assembly it appears to have the Variocam setup. I just did't recognize it. I'll check the engine code to be sure, but I think all is well.

Thanks for all the help.

fast951

John, Which car are you working on black or red?

johntorg

John, actually neither. Its a friends 944 SuperCup car tthat has a 16V 968 engine and blew a headgasket at the track. Both the red and black cars are doing fine. I still have some tuning to do on the Motec in the red car and I will re-charge the AC and use it s a street car for a while. Its actually running well under boost and cruising, but hesitates just a little on throttle tip in. The black car with your chipboard is also running well, but I have to permanently install the SMT6 and wideband, which are currently wired in, but sitting on the passengers floor.

johntorg

Help. The block is an M44/41. What is that? S2? The headgasket is identical to the one in the 968 kit. I also need the torque specs for the cam pulley, cam cover, cam bearings etc.

333pg333

That's an S2 block.

johntorg

Thanks, Its back together now.

gt37vgt

Given the choice I would use a 968 engine .which apparently has forged pistons bolt a gt 30 or 35 to it not open it up and run it on e85

Chris White

Not a good idea...the 968 has weaker connecting rods, the variocam is not a good set up (Cam lobe separation) for a turbo. The 968 pistons are too high a compression ratio for a ‘bolt on’ turbo.

The original post did not mention how much work was going to be done. Here is a list of the differences between the S2 and 968 -
968 has piston squirters S2 does not – can be added for $300-$400
968 has lighter and weaker connecting rods, S2 has the same connecting rods as the 944 turbo.
968 has higher compression ratio pistons (lighter too). Not good for bolt on turbo
968 has Vario cam – not set up for turbo charging – it’s not a true ‘variable’ system, its an on/off set up with a 15 degree change in the intake cam timing. Needs to be programmed differently for turbo use
968 has a hydraulic belt tensioner
968 head has bigger intake and smaller exhaust valves

If you are going to really build a 3.0 turbo motor it doesn’t not make a lot of difference since you will need to make a lot of mods to make it work.
Another note – if you not going to a stand alone system keep in mind that the 968 ECU is a LOT different than the S2 set up.

Jeremy Himsel

Slight correction. The S2 rods aren't the same as the 951 rods and I would not use them in a turbo application. Here's a picture of the difference. The first one on the left is a 90 S2 rod, second is a 89 951 rod, and the third is a pauter.

I used a S2 block for my conversion and added the squirters. The hardest part was sourcing the squirters.

Chris White

Actually those are pictures of the 944 series rods - 1st is a cast rod - it came on turbos and NA depending on year. second is a forged rod - is also came on turbos and NA depending on year...here is a break down....sort of!

82/83 NA - forged rods
84+ na cast rods
86 and some 87 - forged rods
87-89 - some cast some forged. Factory manuals even say you can mix them together in the same engine...!
Turbo S - I have seen both cast adn forged rod in these.
S2 engines...I belive mostky cast but I would not be albe to say for sure, Porsche likes to mix things up.
968 - completly new rod design - much lighter and not as beefy.

fast951

MY 82/83 NA rods are forged, but do not look like the 951 rod.

Every 951 engine I have seen had the forged rods as in the picture. It will be interesting to document the engine code for any 951 without forged rods.

Chris White

I have found that only the 86 turbo engines are 'guaranteed' to have forged rods.
The early 83/84 na rods are only slightly different than the turbo rods – at least the sets that I have seen (I don’t take apart too many early NAs!)
I have been inside several ‘original’ turbo S motors that had cast rods and model year 87 is about 50/50 so far.

Jeremy Himsel

Chris, are you saying that the later 951's or some in general, came with a cast rod or forged rod or some came with the first rod in the picture. While I've been in plenty of these motors (I'm sure not as many as you), I've never seen one that had a rod similar to the S2 rod pictured. I typically don't check the code on rods to see if they're forged or not (unless it's a complete build or the rod is being pulled).

I have a hard time believeing Porsche would use a rod that narrows twords the wrist like like the S2 rod does in a FI application.

Chris White

Yep, the narrow rod on the left is typical of all cast rods...and I have seen them in many later turbo engines (not my first choice either!!!)

Duke

The 968 does not have smaller exhaust valves than the S2, they have the same size. The ports are also larger and it's a better flowing head. The larger ports does not necessarily be better in a N/A configuration but should gain better results than the S2 head with forced induction which I think is proven.
Also, the 968 Variocam has been used sucessfully in a turbo application so I don't see why that is should be a drawback.