Chambers of Cylinder heads 911S and 911E (1967-1969)

[Elferhelfer]

Hello together,
I joined the forum some time ago, but up to now I was less active. Actually I could need some help from you, because I have some question about differences in the chambers of cylinder heads. I couldn’t find proper information about the dome chambers of the 2.0L engines. I know the differences about the valves and ports, but I don’t have proper information about the domes.

I would be interested in the difference between the dome chamber of a 67S, a 1969S and 1969E. Do they have the same shape and volume?

I am asking, because I have a 1969E engine, where I would like to install high compression pistons.

It would be great, if you could help me!

Best regards
Florian

Here are some pictures of the following heads:

911S from 1967 901.104.305.02


911E from 1969 901.104.008.00

[edmayo]

To the best of my knowledge all the 2.0 liter combustion chambers were the same size, given allowable tolerances. Of course anytime you're building an engine, combustion chamber and piston dome volume must be measured for accurate compression ratio results.

[66S]

We substituted one NOS 69S head in a set and found it had an appreciably lower volume than the others which were not flycut. That surprised me but there are production variances.

[Elferhelfer]

Thanks a lot for your answer. For the 911S from 1969 it could make sense, because the compression rate is quite „high“ with 9.9:1.

What would be the best way for measuring the dome volume?

In my project I would like to go for Wössner pistons, which have a compression of 10.5:1. I would like to install the pistons and check with little balls of plasticine for clearance.

[SIMI BOB]

Cut a piece of Plexiglas the same diameter as the outside edge of the top of the cylinder, so it will fit into the recess in the head. Drill a small hole in the center. Apply a little Vaseline around the edge where it mates with the head to keep it from leaking. Install a spark plug. Measure volume with a burette filled with cooking oil. The burette needs to hold at least enough oil to fill the combustion chamber, probably about 50cc. Measure all six heads.
Bob B