Help Me to Identify These Heads?

[tom1394racing]

I have this set of heads in my stash and I am stumped in trying to figure out the application.

Casting # 901-104-306-2R
Casting date - 2&3/70
Casting type - K1819d
Ports - 32/33
Valves - 42/38

They would seem to be 914-6 2.0 liter heads except they they are machined to fit 84mm cylinders. I am guessing that smaller combustion chamber in the 2.0 head would give a nice CR boost for a 2.2 or 2.4 build but I would think that the small valves and ports offset the CR boost.

Anybody ever seen anything like these?

[Dpmulvan]

There 2.0 liter 911 heads

[Dpmulvan]

1969 911t

[Dpmulvan]

or 1970

[tom1394racing]

Originally Posted by Dpmulvan

There 2.0 liter 911 heads

That is what I thought at first. Except that cylinder-to-head sealing surface is machined to accept an 84 mm 2.2/2.4 cylinder not the 80 mm 2.0 cylinder.

[Henry Schmidt]

Originally Posted by tom1394racing

That is what I thought at first. Except that cylinder-to-head sealing surface is machined to accept an 84 mm 2.2/2.4 cylinder not the 80 mm 2.0 cylinder.

Machining 2.0 heads to fit 84 mm cylinders was/is done all the time.
Back in the day, 2.0 pistons and cylinders were more expensive than the 84 mm Ps&Cs and by this simple machine process you ended up with "more power" because of increased size.
Compression becomes a problem because the increased diameter required a slight chamfer be machined in the head to mate the cylinder to the chamber.
Then there's the issue of the deeper chamber (1.75mm) on the 2.0 head and it has a different valve angle.
All told not a great conversion. That is why we invented the 81mm cylinder with the 84mm sealing surface.
The result is a more stable platform and no compatibility problems.
We also reproduce the 906 cooling tin to ensure that these cylinders with increased cooling fins operate at the correct temperature.
The net thing is to increase the valve size from 38/42 to 39/45 69 2.0 "S".

[tom1394racing]

Thanks for chiming in Henry

I figured you would have the answer.

[Dpmulvan]

Seems he be the man