mystery heads

[gumba]

911 104 306 date stamp 5/71 twin plug. intake approx. 37.2mm, exhaust approx. 34.9mm
Thanks for any help.
'74 rsr w/2.8 twin plug

[Nitrometano]

If you look the date, maybe the heads come from a 2.2 engine.

[BURN-BROS]

Are the spark plug holes the same size? Do they use the small spark plugs?

[gumba]

The plug holes are the same size. Small plugs Bosch f3cs.

Thanks,
Harold

[BURN-BROS]

Harold,

This is stuff that you probably already figured out but I'll throw it out there. Sounds like factory racing heads. Ports are smaller than RSR so maybe ST heads. Sound like you got some good parts out of that race motor.

[gumba]

Thanks for the help. I don't have a clue about the heads. The plugs are 14mm so they may be a stock early head someone twin plugged. I was able to look up the serial number on the cams, and "Camgrinder" confirmed it. I figured based on the cams I should keep investigating the rest of the stuff. My plan is to have the motor rebuilt and stick it in my '73 targa for the time being.

[BURN-BROS]

Can you post pics? Take extra care of the crank too. You never know what it could be...

[BURN-BROS]

Here is a pic of a 935 head for reference. note size of spark plug holes

[gumba]

valves are approx. 45/40

[BURN-BROS]

The larger sparkplugs make this a standard head modded to twin plug. Generally they use the smaller plugs to keep as much head material as possible for heat transfer.

[gumba]

That's what I thought. Thanks for all the help.