This! ⬆⬆⬆ EXACTLY!

Porsche had to go to water cooling to get 4 valves to cool in the 70s and 80s and if they could have avoided the complexity I think they would have at least tried to race an aircooled head.

So what did they do?

Well it seems to work very effectively…….

BTW - Here is Swindon's link from their Rennsport display:
https://swindonpowertrain.com/products/24-valve-porsche-911-m64-cylinder-head-kit/

“ The kit has been engineered to fit to a standard engine, and utilise the original cam drive and lubrication system”. Wow!

A bargain! ;)
https://webshop.swindonpowertrain.com/index.php?route=product/product&path=127&product_id=361
But seriously, I don't think we're going to see this kit on many street cars in the near future, who the heck can afford £35,000 for this set up ?

looks like a very desirable mod, but i also wonder how they solved the thermal problems that caused the factory to go to water cooled heads, they do mention materials, Ti valves and space age alloy may be the cure

Remember a lot of the air cooling issues were noise, water cooling was way quieter.

There are a few jurisdictions (Switzerland) where noise could have been an issue but there are a bunch of steps they didn't bother with to try and reduce it further.
But tthe hermal control you can get of the chamber and the whole combustion process that comes from water cooling makes control of emissions much easier (or even possible).

There are multiple advantages to using water cooling, not just keeping the heads cool. I'll guess that Porsche was at a point in development where they decided that the advantages were worth the expense of going that way. Higher boost also drove them in that direction. I don't think it would have been possible to continue with air cooling for boosted engines that develop 200 HP per liter.

All sorts of advancements. Many things come down to cost. You could machine a head today out of many things that you could not cast or machined 10 years ago. You could do titanium, magnesium, ceramic etc. if needed, with either with additive or subtractive machining today that you could not do cost effectively a short time ago. I think what is possibly with these old, old engines is still yet to be discovered, it just comes down to $$$$. future should be fun as more of these exotic things become more commonly available in general support of these old engines.

john

I think the primary reason to change to water cooling was to more accurately reduce emissions. A large majority of these cars are sold in Kalifornia. The leading state in the nation to elect idiots and strangle the economy.

So given that these engines are going 11k rpm, what is limiting my 1983 911SC? Rotating Mass, airflow, case rigidity? Any ideas?

I’m going to go with valve train and then rotating mass to strength ratio are the mechanical limitations. Even these 4 valve heads are airflow limited given that it doesn’t make the power it should for the RPM.

Valve springs, rockers, light valves and good rods with the correct oiling and supporting modifications gets you to 9k with a shorter stroke crank and 2 valve heads.

996/997 RSR go to 9000 and a lot higher on over revs with largely the same bottom end. We used to see 11,000 rpm over revs with the engine surviving on 996 and 997 Cups.

Stiffer case and crank are never going to hurt.

24 Valve Engine
 

Has anyone purchased one?