Carrera 3.2 heads vs the 930 turbo 3.3 head
 

Can anybody tell me what the difference between the Carrera 3.2 head and the 930 turbo heads. Is it the valve size. Was wanting to twin plug a 930 engine but had opportunity to get twinplug 3.2 heads. Would these work. thanks for the input. I would like to retain the original set as original. thanks rob

some reading material ...

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/524341-3-3-vs-3-2-cylinder-heads.html

http://forums.pelicanparts.com/porsche-911-technical-forum/189448-truth-rumor-930-vs-3-2-heads.html

could someone list the inlet/exhaust valve size:

930 3.0
Inlet = ?
Exhaust =?

930 3.3
Inlet = ?
Exhaust = ?

3.2 heads
Inlet = ?
Exhaust = ?

Valve sizes are all the same from 3.0 to 3.3.
Bruce

So 49mm inlet and 36mm exhaust valves on all 3 heads ??
I read in other posts that the heads should have difference in e.g. exhaust valve size...
Could some one confirm
thanks

Hi.

The valve are same size, but the port size are different 3,2 are 40 mm and 3,3 turbo are 32 mm.
And I think I hear Henry talk about the materiel is different, 3,3 are better.

Daugaard

Thanks, I understand the port shape/size is different on all three heads
Alu is different on both the 3.0L and 3.3L 930 as I understand
having the valves at same sizes both in/out should make it reasonable to port existing 3.0L 930 heads and twin plug

A couple other differences too.
The 1976 930 heads exhaust ports are 34mm or 2mm bigger diameter than the 1978 heads onward. Maybe the 1977 heads too I don't know.
Not in the stepped inlet area where the headers fit in but inwards just beyond that. I have some and measured them with calipers.
It also states that for the 1976 930 heads on the specification page in Wayne's engine rebuild book.

Another thing is the 1976 930 heads machined for 95mm bore cylinders do not have the "RR350" cast into the head like the later 97 mm bore 3.3 liter heads.
I don't know if that means they didn't start using the P51 mustang aircraft Rolls Royce Merlin V12 engine RR350 aluminum alloy for the heads until after 1978 and the years after that or maybe they just didn't start casting it in there until '78.

Out of curiosity I'd like to know if the '76 930 heads use the same alloy as 3.2 Carrera or SC heads or do they use the higher temp compatable RR350 alloy.. and those letters and numbers just weren't cast in until 1978 onwards.

My guess is nobody really knows and it will remain a mystery and it doesn't matter for a street car anyway.