Ed Bighi

A while back someone here on the list was asking about 4-valve heads. Well, I think I just stumbled onto something interesting. If anybody read through this month's "911 and Porsche World," there is an interesting article about Dean Polopolous and his custom made 911 based 4-cylinder conversions for 356's. That is an achievement in itself since at first he would cut the crankcases, cranks and cams of a flat-6 and reduce it to 4-cylinders and use it in a 356. Of course, one could use any injection, turbocharging and bigger diplacement kits for 911's on those to make a super fast 356.

Well the guy now has the crankcases already cast in 4 cylinder configuration along with billet 4-cylinder cranks and cams. Amazing stuff. But what really got me going was the article mentioning that his current project is one of these motors based on 3.6 components, with a 2.4 liter displacement, twin-plugs and 4-valve heads. That's right, 4-valve heads. Common sense would dictate that if those heads would fit on his flat-4, they would fit on a flat-6 since his flat 4 is basically a reduced 911 flat-6. I hope I am not getting excited over nothing, but I have my fingers crossed.

Chris Bennet

Years ago someone in Germany was selling 4 valve 911 heads. I think I read about it in Excellence magazine. The guy had big gold rings hanging on the wall of his establishment. They were some sort of award for lapping the 'Ring in record time or something.
-Chris

PorschePhD

Ed,
Not sure if Chris is talking about the same guy, but in the 80s there was a guy in Canada that had come up with a 4 valve setup. Several well respected people in the industry tried them and the flow as simply terrible. Great idea, but never got completed or stayed together and the gent stopped making them. I believe I know a guy that may have a set if you were looking for them.
Stephen

John Liu

I remember reading a thread (here or Pelican) where the posters stated that 4-valve heads on 911s have cooling problems, and pointed out that all factory four-valve heads have been water-cooled (959 and various racers).

Elephant Chuck

Your going to need 4 valve cams too. Those 4 cylinder cams will come up short.

A Quiet Boom

I've been amazed in the reading I've done about aircooled 911's that the factory never sought to implement watercooled 4 valve heads on the turbo models. The increase in longevity alone would seem worth it and they probably could use a very small radiator. When you think about it they could be one solid unit with the cam towers and heads for each bank cast in the same mold ala standard watercooled cars. Oh well another good idea that never made it to production.

Ed Bighi

The 959 had 2 water-cooled 4-valve heads. One on each side. The 962 had 6. The GT1 used the same ones as in the 959. So does the GT3 and 996 turbo since those cars use the crankcases from the air-cooled 964/993.

But I still prefer an entirely air cooled setup for simplicity and elecance in execution in an air cooled 911. Andial though, did put in a detuned 962 motor in a 964. I think the flow and cooling are issues that can be resolved with time and effort. You need the right person with the right money for that endevour. Somebody will pull it off and maybe Dean Polopolous is the man.

emcon5

The 935/78, AKA "Moby Dick" had them too, welded to the jugs, if I remember correctly.

Tom

Ed Bighi

They also welded the air cooled heads onto the jugs of the air-cooled 935's. I think they started that with the 3.2 twin-turbos. With that little modification, head sealing failure due to very high boost was a non-issue.