SC heads on a 930

[gpitts714]

I am considering replacing my stock heads with big port heads from an SC. Can anyone tell me if this is a simple bolt on modification? I am also planning on installing SC cams. Any information regarding this modification would be greatly appreciated.

Thanks

[Flieger]

930 heads have a better, more heat-resistant alloy. Bigger ports mean worse performance at low speeds and low boost.

[911nut]

Others on this board have run SC heads with no issues.
The larger ports are a must if you want to make big hp numbers but as mentioned, low speed performance will suffer. Fueling is also an issue if you are staying with CIS; changes to the fuel head will be required.
SC cams are the wrong choice for big port heads. Cams with lots of duration will take the most advantage of the big intake ports.

[aseem]

What about the Carrera 3.2 heads? I think they are usable as well. Then you can use the 3.2 intake as well.

Any one with experience?

[DPHANS]

Hej Gutten.
I have SC heads and SC camshafts from 204hp engine, and this works fine.
I added with twin turbos and a "poor mans" CIS system.
PS. you must have a comp,ratio at 7:5

DPHANS

[cgarr]

Don't know about the alloy? They looked pretty much the same to me except for the port size and they run the exhaust valve a bit looser.

[gpitts714]

Thanks for the replies so far. If SC cams are not a good choice what is a better choice? From what I have read, 964 cams do not work well until higher RPM's. Should I just stay with the stock cams?

Thanks

[spuggy]

Originally Posted by cgarr

Don't know about the alloy?

The 930 heads use a (trade-marked) alloy under license from Rolls Royce known as RR350 - this symbol is cast on the 930 head. RR350 is also known as AMS225B, and used for bearing support housings in more than one gas turbine motor. Which sounds like a fairly hostile environment.

Bill V says in one thread that he suspects the standard alloy in N/A heads (pre-993) is AMS4220. AMS225B (RR350) is rated for use up to 600F and AMS4220 is rated up to 400F.

Might just be over-engineering by the factory (like the 10 pound recirculation valve assembly). Many folks - including the big HP guys - seem to be running SC or 3.2 heads without issues.

That said, the factory apparently used RR350 for 993 heads (together with ceramic exhaust ports).

they run the exhaust valve a bit looser.

Isn't heat transfer from the exhaust valve primarily through the guide? I thought a turbo failure mode was the guides wear beyond spec, the exhaust valve stem locally overheats and the valve head drops off into the combustion chamber. Ouch.

The 935 had an oil channel drilled into the exhaust valve guide which I believe was intended to address precisely this problem - but apparently it's only really essential for the Mulsanne Straight..

[spuggy]

Originally Posted by gpitts714

Thanks for the replies so far. If SC cams are not a good choice what is a better choice? From what I have read, 964 cams do not work well until higher RPM's. Should I just stay with the stock cams?

Thanks

You'll get better mid-range with SC cams than 964. If you're sticking with CIS, I'd use the SC cams and not sweat the compression. It'll give you much more safety margin under boost and you'll never notice the difference off-boost anyway.

Twin plug is a no-brainer, according to Steve Weiner.

[Kraftday]

Lots of recent cylinder head data shared and outlined here:

2010: An EFI Hot Rod Odyssey

Thanks to Tom!

[Flieger]

Originally Posted by spuggy

The 930 heads use a (trade-marked) alloy under license from Rolls Royce known as RR350 - this symbol is cast on the 930 head. RR350 is also known as AMS225B, and used for bearing support housings in more than one gas turbine motor. Which sounds like a fairly hostile environment.

Bill V says in one thread that he suspects the standard alloy in N/A heads (pre-993) is AMS4220. AMS225B (RR350) is rated for use up to 600F and AMS4220 is rated up to 400F.

Might just be over-engineering by the factory (like the 10 pound recirculation valve assembly). Many folks - including the big HP guys - seem to be running SC or 3.2 heads without issues.

That said, the factory apparently used RR350 for 993 heads (together with ceramic exhaust ports).



Isn't heat transfer from the exhaust valve primarily through the guide? I thought a turbo failure mode was the guides wear beyond spec, the exhaust valve stem locally overheats and the valve head drops off into the combustion chamber. Ouch.

The 935 had an oil channel drilled into the exhaust valve guide which I believe was intended to address precisely this problem - but apparently it's only really essential for the Mulsanne Straight..

Good summary of useful information.

[911nut]

Originally Posted by spuggy

You'll get better mid-range with SC cams than 964.

Mid range, as in 4000 rpm? My SC didn't come on the cam until then and it wasn't very much fun to drive.
If your going to go to a cam with overlap (which hurts low speed performance) and more duration, why not go all in with the 964 cam like the factory used in the Turbo S?

[spuggy]

Originally Posted by 911nut

Mid range, as in 4000 rpm? My SC didn't come on the cam until then and it wasn't very much fun to drive.

No, I'm not talking about "on the cam", and I don't consider 4,000 RPM "mid-range" for a 930 - my 930 when "almost stock" (but with SC cams) made peak power @ ~5700, what do your dyno charts say?

Motors with SC cams don't need to be "on the cam" or "on boost" to be drivable. You floor the throttle at 2000 RPM, they do something, they make torque, they go faster.

An RSR isn't "on the cam" until 5,000 RPM - you would be extremely unhappy driving that in traffic, because it makes no power at all until it is "on the cam".

964 cams - it's not a race cam, but they are more oriented towards top-end performance than SC cams. They were designed for an EFI motor - which helps you give up less below the power band and can get away with this.

If your going to go to a cam with overlap (which hurts low speed performance) and more duration, why not go all in with the 964 cam like the factory used in the Turbo S?

AFAIK, the factory used SC cams on the 930S?

You can use 964 - but you give up more mid-range in favor of a tiny bit more top-end - which, on a turbo motor, there are lots of other ways to make up anyway.

[WERK I]

Originally Posted by spuggy

...........................snipped for space........................
AFAIK, the factory used SC cams on the 930S?
.................................................. .........

The 930S (circa '87-'89) used the standard 930 cams that came in all 930 engines.
The Sonderwunsch engine (rated 330BHP) had different cams, but I don't know what the cam profile was. It does have the SC casting numbers on them, but don't know if the the profile was tweaked by the factory for the engine. I forgot to look at the end of the cams to see if there was special stampings when I rebuilt the engine.

I do know it comes on "cam" wonderfully around 3K RPM.

[Flieger]

I agree with what was stated above. The small ports and cam profile for the Turbo were meant to get back some torque down low in the rev range which had been lost due to the low compression. At higher revs, the boost cures all.

[lite75]

I ran 964 cams before converting to efi. They worked great, even in the mid range on a 3.0. You do need to raise the comp otherwise the mid range will suffer.

[zcoker]

I have custom cams by Elgin, a sort of super SC and, man, do these cams put you back into the seat and pull all the way into infinity. Low end is a blast and so is top end, kind of the best of both worlds. It is the timing of the cams that makes a huge difference, not just the cam itself, or whether it comes on at a particular rpm range - this can all be altered or timed to the engine configuration.