Oddjob

$1654.86 from a Dealer; still 17 brand new ones on the shelf in Germany.

hosrom_951

Is that for a bare head, or with the hardware (springs, retainers, valves etc).

DC-Auto is selling a complete head w/hardware for that price.

But having a bare head is what is needed, since you would need to replace the valves and springs for a turbo set-up anyway.

StyleLab

that is the bare head price

Oddjob

The factory new heads include the plugs, dowel pins, valve seats, and valve guides. The valves, springs, retainers and seals are not included.

RajDatta

How about the oil relief valve? I know its very expensive. If its a bare head, it would easily cost upwards of another $1k to make it ready.
Raj

931guru

Yes, the intake valves are unobtainium from Porsche, and nowhere else!

evil 944t

Thats ok, there is nothing special about them. Its very easy to put a better valve in there. You just have to be creative.

dand86951

Here is a dyno chart with 16V and 8V overlaid that shows the differences in torque and resulting horsepower vs rpm.

http://www.powerhaus.com/images/968t16v/dyno1.jpg

Geneqco

That's a great post - very helpful, thanks. What turbos were used on each?

Looks like 16v is quite a bit better off boost. Any thoughts on the overall package comparison: better off boost with mid range sacrifice for the higher top end?

Geneqco

Thanks Chris, I guess I'm trying to guage how much more efficient the 16v is in design. I understand the fast burn chamber design of the 16v means you can run less spark advance and therefore make it less suceptible to detonation. If you were to choose a few points on the timing map for each, assuming similar boost etc, how much less advance would you be running with the 16v? Or better still, what would be the advance for each?

Thanks

Porschefile

Haha. That's why you don't buy valves from the dealer. Any good quality 21-4N grade stainless valves from a reputable manufacturer (Ferrea, Manley, etc) will work just fine, and in many cases will be of superior metallurgic properties, heat dissipation and tensile strength. Stock isn't always the best or the cheapest.

The 944/968 16v heads are superior in every way, shape, and form to the 8v's except in terms of overall cost and custom work required. It's too bad that there isn't a larger market for the 16v stuff to make things a bit more cost effective. Personally, I think that if someone's going to spend say $15k+ on a motor then it's an absolutely horrendous and disappointing thing to throw a crappy, old, inefficient 8v head on it kind of like wearing a $10,000 suite and Nike's. The 8v's certainly make it easier as parts are easier to adapt (you can use lots of stock stuff), but they are significantly less efficient in combustion chamber design as well as overall airflow volume. Judging by what I've seen, according to LR and several others the stock 8v 951 heads flow ~180-190cfm intake and ~190cfm exhaust in stock form. For a turbocharged motor, those numbers aren't all that great, especially when you start modifying and reaching increased power levels. Now, I have yet to see a flow chart for any of the 16v heads but, I've heard a range of numbers thrown around by several individuals here around ~300-320cfm intake from the 16v heads, though I'm not sure on the exhaust side. Without having a flow chart, it's all speculation at this point, by I heard it from enough independant individuals that it seems plausible and at least in the ballpark. That's a significant amount more airflow volume then the 8v's, and would have hugely beneficial effects. The one very important factor I haven't heard any numbers on in regards to the 16v heads is airflow velocity. It could be they flow so much more due to over-sized ports, meaning significantly decreased airflow velocity (that's my theory) but, who know's. Either way, from a performance standpoint the 16v is ultimately superior. That being said, the 8v's still get the job "done" so they work just fine at the cost of a bit of efficiency.

Luke

With force induction... may as well stick with the 8valver.

Unless you want to spin the motor real fast and make HUGE numbers. (which a fast spinning 3 liter that's reliable doesn't sound financially feasible).

MPD47

Geneqco

Yes, airflow velocity is something I'm interested to know more about... looking at the overlaid dyno chart, it would appear to not be an issue for the inlet side - better TQ before spool up. However, it does not build TQ/Boost as quickly which suggests to me there is significantly slower exhaust gas velocity.

Any comments?

Fishey

That seems like a pretty strong statement for it to be so incredibly false.

well, except the huge numbers part..