We're in the process of putting rods in our 997.1 and going for more power. While the engine is apart I took the time to put both the intake and exhaust camshaft from the 997.1tt and 996tt on our cam measuring equipment to see what the difference is.





It seems that people say they are different and it's one of the reasons why the 997.1tt makes more power and has a better power curve than the 996tt. What do you guys think? I'll put the answer along with cam specs for both later this afternooon.

Best regards,

Martin Musial

 

Disappointing that no one has responded here! There are those of us who are very interested in what you are up to Martin .

 

Looking forward for results...

 

Sorry I started a thread in the 996turbo section also and forgot to update the one here.

And...here we go.



They are exactly the same. Here is graph of intake and exhaust valve lift vs crank degrees. It looks like there is only 1 intake and 1 exhaust profile. There are two of each it's just that they lay over each other exactly. Disregard the lobe center-line and lobe separation angle, i did not measure these (you really can't unless you time the engine per Porsche manual and then measure in the engine), just the lobe profiles themselves.



Here is the cam card, again disregard the LSA and Lobe center-line angle. I'll chime in more on the cam profile tomorrow.

-Martin Musial

 

Excellent, there should be more posts like this.

 

Intake and exhaust valves are the same. Part #'s are the same in the Porsche parts system and we verified by looking at the two heads.

Chambers look the same, the ports look the same also. The 997tt is for sure a different casting and it the intake/exhaust ports look to be .010"-.020" larger on the exit but that could be a casting/core variation.

There is some more external webbing like people have mentioned. The valve job, and more specifically the blending of the bowl area to the seat is nicer on the 997tt.

There is something interesting in the coolant passages on the 997tt head. It has a different port configuration on the exhaust side and there is coolant passage that leads to an area behind the quench pad (the area behind the exhaust valves). It looks like they did this to help keep exhaust valve seat/valve temps down and reduce hot spots on that side.

As far as power potential/VE the heads look to be about identical including hardware.
I one thing I'd like to check is the cam timing between the 996tt and 997tt. There are no dowel pins or keyways to fix cam timing to the cam gears. This is very strange and you basically have to time the cams in the engine and then lock the cam gears to the cams. This takes any tolerances out of the system and you should have a perfectly timed engine with cams every time you put it together. I'd like to see if they specify the same timing on the intake cam for each engine. There could be a potential difference if the 997 was timed to allow more cam retard and the engine could make more power up top because of this.

-Martin Musial