progenitor04

has anyone ever shaved, port, and polish there head? becuase im thinking about doing it and i need to know my limits on doin them and if theres a template of some sort..if any one has any info on this it would good

Bill Gregory

As I recall, Bruce Anderson talks about head modification in his "Porsche 911 Performance Handbook".

Geoffrey

Which engine are you referring to? In general, 911 engines allow for 2 cuts of .010" each for a total of .020". Regognize that you'll increase the compression ratio slightly, lose some valve to piston clearance which may be an issue if you run larger lift camshafts and weaken the sealing surface due to the cooling fins and lack of material of the fin closest to the head surface.

ngoldrich

Also, be very careful how much of the material you remove from around the valve guide. I have seen people remove too much and the remaining aluminum actually cracks; leaving the valve guide not properly supported and leaking oil into the combustion chamber. It destroyed the set of heads.

Norm

IrocMan

I agree with Norm, working on air cooled 911 head is a very delicate thing.
However there are different strategies to have a better flow

IrocMan

We forgot to ask for what engine it is !!!
Maybe it's to tune a 944 engine ?

IrocMan

There is a safe limit I have for a 911 (pre 964) head.

here a 3.2L engine being rebuilt and a bit tuned :


with valve in place for the flow bench at different lifts before to make the finishing :


at flow bench this gives a good gain without removing too much material.
You have to spend about 30 min per port with a good set of tools.
The valve lift and shape restrict the amount of air passing through the intake. The butterfly is also a restriction and must be optimized.
Note that a good valve and cam design are very important to take advantage of tuned ports.

Luc

progenitor04

thanks for all the information but its a 1987 944 N/A im sorry i should of said this before i guess i didnt realize it