Apex

Can anyone shed light on something I hear from time to time, that the 968 engine was 1/2 of the 928 V-8?

A friend of mine is rebuilding a 928 engine and I was looking at all the "action" in his garage this morning. He's pulled all four camshafts and sure enough, each seems to have a variocam mechanism like our 4-cylinder, 2-cam head. Same brown pads and all.

I thought the 968 was the first variocam-equipped car.

If so, might it be more accurate to say that a 928 is a 968 3-liter doubled? Did the 928 build on 968 technology, or was it the other way around?

RajDatta

Jeff, what you are looking at is the chain tensioner. They look deceptively alike. The mechanism they use is very similar to 944S2 where the tensioner just provides static tensioning. The variocam tensioner provides dynamic tension by tensioning the upper or the lower half of the tensioner and in regards, advances or retards the timing on the intake camshaft. The exhaust camshaft stays static and is driven by the cam belt. Essentially a 928GTS is half of a 944S engine(2.7 16 valve x2 = 5.4 16 valve). The pads on an S and an S2 are same part numbers but the tensioner itself is a little different and the amount of tension it provides is a lot less on a 928 cam chain.
I have a neat idea for the 928 guys. I see them boring and stroking their engine to 6.0 liters all the time. Why not just use 2 968 heads with the variocam, use a 968 harness to trigger them, split the signal to both banks and see what you come up with. I would say atleast 450-460hp with atleast 450lbs/torque. See what your friend thinks.
Regards.
Raj

Jay Wellwood

In as far as using the 968 heads on a 928 block - there is a bit of mismatch for the oil and water ports that provides a problem.

One of the 928 owners did bore & stroke the motor and incorporated the 968 cam gear on his cams. Then he welded the cam gears such that he could make adjustments on the dyno and determine the best setting. Once this was done, he permanantly fixed the gear on the intake cam.

There is a variety of configurations for the 928 motors - boring out to 104mm and increasing the stroke to 95.75mm yields ~6.4 liters. These configurations are getting ~500rwhp and ~500 ft-lbs. These numbers are not the result of increasing the displacement though - there are a few 'other' things that go into it.

RajDatta

Jay, I would be interested to learn what other trick are incorporated. That must make one hell of a car to drive. 500plus rwhp is a heck lot of power.
Raj

Jay Wellwood

Raj-

Mods to the exhaust (removing the Rear Muffler) (Cat Bypass tubes) (Headers - although this don't really do much) are a few things.

Minor changes to the cam timing - advancing the cams really just shifts the curve up though. Don't think that this can be done on the 4 cylinder motors - but I haven't verified this yet.

Using the GT Cams provides quite a bit bang for the buck as well. There are some custom profiles out there - but I'm not certain as to the actual bang for the buck.

Right now, there is alot of experimenting with mods to the Intake with pleasing results.

Besides those listed above - there is the Supercharger guys - they too are also getting big numbers using the forced induction route. Numbers are consistently around and slightly above 500 rwhp (current leader in this group is 525 with ~12 psi boost!).

Apex

Sterling you are certifyably insane! We don't believe your over-modest protestations about "not being a mechanic" either!

But... you have an amazing car, that's for sure. Lots of love being poured into that baby.

Thanks Raj and others for your replies!

flash968

what you heard, and i hear as well from time to time, is talked about in "Porsche 924-928-944-968" by David Vivian - on page 66 it talks about the 944 engine being a sliced half of the 928 engine

then the generational progression to the 968 engine happened from there