Early 911S? Heads

[811SWB]

I'm in the process of building a 2.0L Modified Street Engine and I originally wanted to use the larger 1969 911S heads which I can't seem to find. I came across a set of carburetor heads which have a casting number of R901.104.305.02. I could not find this casting number in any of my reference books, here are the specs I was able to retrieve:
Cast# R901.104.305.02
Fuel Type: Carburetor
Intake Valve: 42mm
Exhaust Valve: 38mm or39mm
Intake Port: 35mm
Exhaust Port: 33mm
Production Date: 6-66
Cast Mark: K1819B

These heads are close to 1967/68 911S Specs but both ports are slightly smaller
35/33mm vs 36/35mm and they have the earlier 1964-66 casting numbers and markings.

Does anyone know what 911 engine type these were used in?

[Flieger]

With all those numbers you should get an answer right away by searching or posting here:

Early 911S Registry

[Jon B]

You have '67S cylinder heads. They are slightly different than '68S heads, which had cast provisions for air injection nozzles.

Cylinder head castings:

R901.104.303.04..... Standard 911, '64-'67
R901.104.305.02..... 911S, '67
901.104.305.OR....... 911S, '68

[Steve@Rennsport]

'69S heads are now VERY rare and difficult to find.

If you have the budget, those heads can be fitted with the larger '69S seats and the ports flowed to match (or better). The hard part now are valves which must be custom made.

[811SWB]

Is there a difference between 1967"S" heads and the ROW 1968"S" heads?

What are the port size openings for the 1967?

What are the port size opening for the 1968?

[Jon B]

Specs for both '67 and '68 911S heads were identical, but castings were different. Model year '68 heads had cast provisions for air injection nozzles. Photo below is a '68S cylinder head, with cast relief for injection nozzle. US '68 model 911's were equipped with air injection, but there was no official US model '68 911S.

Original 1967/68 911S cylinder heads DID NOT have 36mm intake, 35mm exhaust ports, in spite of what some modern books state. The original port sizes were 35mm intake, 33mm exhaust. Second photo below is from the Porsche 911 Workshop Manual, page SE2. Unfortunately the metric port figure is a typo; the inch dimension listed corresponds to 33mm. I've never seen a factory publication, printed in the day, that lists the port sizes as 36mm/35mm for these early heads.

[blue72s]

Hey Jon B,

I know this is an old thread but I have a question - were there any differences between the '68S and '69T heads (casting no. 901.104.306.2R) besides port diameters (32mm intake / 32mm exhaust)?

Was the '69T head made from the same Y-alloy as the '68S head, and did it have the same combustion camber volume?

[Flat6pac]

The valves were different. The 69 S has one year only valves.
Bruce

[blue72s]

Thanks Bruce but I asked about the '69T heads, not the '69S ones.

[ajwans]

Jon, you are correct again. I just measured my 67S heads and found exactly what you said 35/33mm ports. I have the Y-alloy K1819c part without the air injection port.

andy