4 valve 911 heads??

[speedingbullitt]

Hey...does any one know what became of the aftermarket 911 4 valve heads. The picture in Bruce's book calls the advantec?? I have to look again to be sure. I also rember seeing an article on them in European car magazine 10 to 15 years ago. Any one have info on this subject?? If I remember from that article some one bought the rights to the head and was in canada but more developement work was being done in germany. Was heat the issue...or some thing else?

[Porschephd]

No heat was the issue. They would not hold up. Or at least that is the story. Great idea, just never was perfected.

[Porschekid962]

the porsche 959 was air cooled and had 4 valve heads. why not adapt those?

[ChrisBennet]

Originally posted by Porschekid962
the porsche 959 was air cooled and had 4 valve heads. why not adapt those?

The 959 was air cooled but I think the heads were water cooled. Not sure.
-Chris

[911SCfanatic]

That's what I've read also--the heads were water cooled.

[Porschekid962]

thats even better!!! just like the 935 and 936 that made gobs of power, now we need to find a set of 959 heads and cam towers oh the craziness!

[KobaltBlau]

And a way to put a water cooling system in the car for the heads... Why not just put in a GT3 motor?

yes, 956 and 959 heads were 4v and water cooled. I don't believe porsche has ever made an air cooled 4 valve head. Motorcycles sometimes have 4v air cooled heads, it definitely tends to increase the angle between the valves to get decent cooling capacity, which sometimes screws up the combustion chamber geometry. I think honda '60s F1 motors also had air cooled 4v heads.

Here's a relevant older thread:

which reminds me: why can't air cooled eng have 4 valves ...

[Porschekid962]

So which cylinders can you bolt the 959 heads to??? Sounds like this would be a pretty fun project!

[KobaltBlau]

In frere's book they look like regular Mahle cylinders with no head gasket, like carrera 3.2 cylinders, but they definitely might be special.

I think it would be easier and cheaper to put a 996 GT3 engine in an original 911.

[snowman]

I have talked to a Porsche engineer on this subject. He stated the following: " you cannot get over 280 reliable HP out of a Porsche without going to water cooling". Based on what Porsche has sold over the years I do not see any reason to doubt this statement.

[911pcars]

I'd be very happy with 280 hp if it required 4 valves/cyl. Should have fewer issues with valve float, better breathing and better valve control all the way up the (probably higher) rpm range. What's max HP on a 2.7-3.0 w/2 valves/cyl.? Pretty shy of 280 I should think.

Other than added complexity (and cost ), I don't see how adding 2 more valves per cylinder in itself produces more heat. If an engine produces 80 more HP, that in itself creates the heat, 2 valves, 4 valves or Turbo. I realize things can get a little warmer with increased compression, but this wouldn't be unusual for twin valve cylinders at 10:1 anyway.

Still, there's no substitute for cc's.

MHO,
Sherwood

[ChrisBennet]

Originally posted by 911pcars
Other than added complexity (and cost ), I don't see how adding 2 more valves per cylinder in itself produces more heat.

My understanding is that it's not that it produces more heat so much as that it can't get rid of the heat with 2 more big holes in the head.
-Chris

[KobaltBlau]

Originally posted by ChrisBennet
My understanding is that it's not that it produces more heat so much as that it can't get rid of the heat with 2 more big holes in the head.
-Chris

Yes, and all the associated valve gear. Less room for fins, especially in the central spark plug area where you really need them (to cool the valve seats and the head surface between the valve seats).

[1fastredsc]

Originally posted by snowman
I have talked to a Porsche engineer on this subject. He stated the following: " you cannot get over 280 reliable HP out of a Porsche without going to water cooling". Based on what Porsche has sold over the years I do not see any reason to doubt this statement.

Don't turbo's put out a hefty amount of more power?

[KobaltBlau]

I assume the engineer and snowman were referring to naturally aspirated engines, the figure is certainly in line with that.

[911pcars]

I think we can agree that boosted engines run hotter than NA engines. The cylinder head temps are higher as are their combustion and exhaust gas temperatures. So, relative to a non-existent 4-valve 911 engine, would the temperatures of a turbo engine be higher or lower? If turbo temps are higher (should be), then that might be acceptable for a 4-valve engine putting out 280 HP. Perhaps not acceptable, however, for a manufacturer like Porsche to develop. They would expect much longer service life from a NA engine. Plus, they had water cooling as a backup for the next bump in HP/torque.

For the enthusiast, a shorter life span may be acceptable, implicit by the number of modifications available in the aftermarket, many of which increase power and place more incremental stress on an engine.

I doubt we'll see a 4-valve kit developed since 300 HP is readily attainable with 3.4, 3.6 and larger engines and at a more affordable cost than a 4-cam head conversion kit would probably end up.

Sherwood

[snowman]

My guess as to why Porsche sells boosted engines at higher power than NA engines is that operation at the higher power is somewhat transient, ie you are not on the boost all the time. More HP equals more heat. MOre heat equals shorter lifetime. two valve, 4 valve, 5 valve whatever, its the HP that makes heat.

[Porschekid962]

Could the 959 heads be bolted onto lets say a 964 3.6 litre engine? NA engine though.

[911pcars]

I don't know if 959 heads are available, what they might cost or even if they'd fit on a 911 crankcase, but one could probably develop water cooled heads for less.

Now there's a little project for someone.

Sherwood

[1fastredsc]

Originally posted by snowman
My guess as to why Porsche sells boosted engines at higher power than NA engines is that operation at the higher power is somewhat transient, ie you are not on the boost all the time. More HP equals more heat. MOre heat equals shorter lifetime. two valve, 4 valve, 5 valve whatever, its the HP that makes heat.

Or maybe more of a compression/high rpm thing. After all, your not always at WOT either. Plus this is considering emissions is a problem too since factory engineers cannot consider running the motor "open" in there design unless they are on the race team.