Are Heads position dependent ?

[drwhosc]

I have a 2.2 engine, and I have collected some spare parts. A long story, but I now only have 4 heads. the engine is an MFI, and wondering if I can find two heads do I have to worry about their position, or are they all interchangeable.

Thanks

[SIMI BOB]

Every cylinder head on an individual 911 motor (and 912) are exactly the same, and interchangeable from one cylinder, or from one side, to the next.
Pretty sure that all 2.2 and 2.4 heads have the same combustion chamber and 46/40 valves. The T and E have 32/32 intake and exhaust ports. The S has 36/35 in 70 and 71, and 36/36 ports in 72 and 73.
The exception here is the 70 914-6 head, with 42/38 valves.
Bob B

[Kris Clewell]

I imagine as long as the combustion chambers etc as mentioned are the same, you'd just have to check the deck height so they all torque down the same to all the cylinders. A machinist would be able to check the heights for you.

[SIMI BOB]

Kris,
Deck height is usually referred to as the distance from the top of the piston to the top edge of the cylinder, which is easy to measure with flat top pistons, and not so easy with the Porsche domed pistons. Also, each cylinder should be measured from the base flange to the top edge to make sure they are all the same for a given side of the motor.
What probably is very important here is that all the heads have the same measurement from the cylinder seating area to the rocker box seating area. If some of the heads are fly-cut, there could be enough difference from one head to the next to cause the rocker box to not seat on the heads and cause an oil leak, or in an extreme case bend the rocker box.
If I were "drwhosc", I would procure two used heads and then send the whole set to a competent shop for rebuild, and make sure all the combustion chambers have the same volume and the measurements from cylinder seating surface to rocker box plane are the same.
Bob B

[Kris Clewell]

I just figured it would be good to have them all seat properly and evenly on the cam tower.... guess I used the wrong term.