Geneqco

Well, the time has come for me to seriously consider a 16v head (for my 951).

I have already done a bit of research on this but all I really have are some pretty vague figures. What’s really appealing about the 16v to me is the more efficient chamber design. From what I understand, because of this, you don’t need to run as much timing advance (all else being equal) so there is less opportunity for knock – ie, you can run higher boost and/or use a higher CR to start with. The stronger 3.0l block would also help here.

As for flow and costs… I’m pretty clear on the 8v… around 180 cfm stock and around 250 cfm for Stage 3 and I know the costs. I also have an idea of what 16v heads go for but don’t know their stock flow rate or the cost of working on them or solid lifter conversion costs etc. I’ve heard that they can flow well over 300 cfm with work but I’m not sure what’s involved to get them to that point. I’ve also heard that a stock 16v will flow much like a heavily worked 8v but not sure whether that’s true.

The only other thing I’ve heard about the 16v is that there may be some reliability issues with the chain guides and tensioners and that the variocam system in the 968 setup can also be the source of problems and catastrophic failures which sounds a bit scary.

Any info available on the 16v setups to help me fill in some gaps would be greatly appreciated.

TF

I don't believe it will just fit without some machine work. I think the water jackets don't line up.

Geneqco

Sorry, I should have said... this would be for a 968 or S2 block.

RajDatta

When we did a 16 valve turbo conversion, we opted for an S2 top end setup. You might want to consider that as well.
Raj

ryan@usaimage.com

The S2 doesn't have the problem Variocam. The tensioner is a cheaper, simpler item as well. As long as you replace the guide "slippers" as a maintenence items and the whole tensioner and chain @ 100k or before, the head is solid.

Ryan
87 944S
92 968 cab

FRporscheman

How is Variocam a problem? The Variocam tensioner is more reliable than the S2 tensioner, and if you don't want the variable valve timing, just leave it unplugged. Also, the VC tensioner mounts on 2 sides and is secure, while the S2 tensioner mounts on 1 side and has been known to get ripped off the head.

The only advantage I know of in using an S2 head is cost. This makes it a good candidate for setups with dual exhaust cams (i.e. chain delete + dual cam gears).

RajDatta

Arash, you bring up a good point. Its recommended that you modify the tensioner mount for added strength. This is a well known weak link with the S2 tensioner. They can sheer off in some instances.
Raj

968workaholic

If you use an S2 head with an S2 tensioner, there won't be an extra casting on the head to use as a mount for reinforcing the tensioner. Another plus of a 968 head is larger ports as well.