Carrera heads better?

[MikeHall]

Seems like I saw where the 3.2 heads are better than the 930 heads. I need to get my 930 heads rebuilt which looks to be around $800-$1000 but should I find some 3.2 heads to get rebuilt? Im not sure if im going EFI or not so would the 3.2 heads even work with the 930 instake setup? There is nothing wrong with my 930 heads but I would like to upgrade while in rebuilding if 3.2 heads are a upgrade.

Mike

[sand_man]

I think Craig 930 RS is running those heads on his 3.4L engine. I can't remember, maybe they're SC heads...

[DDDD]

I know that the 1976 930 heads are made out of better material, aluminum, I believe. So people like to bore those out.

I am not sure about the 1978 and up.

I think that it may make no difference whatsoever to you and you should just use the most convenient/cost effective solution. But I believe that the turbos are know for having more heavy duty heads.

A lot of the time, 3.2 heads are already sized correct for the upgrade, hence their advantage.

[MikeHall]

Yeah I guess thats true. I think the 3.2 heads have larger intake ports as well where the 930 heads have to be port matched to the 3.2 intake if I go EFI. Im just trying to figure all this out before I start having parts rebuilt.

Mike

[equality72521]

Originally Posted by sand_man

I think Craig 930 RS is running those heads on his 3.4L engine. I can't remember, maybe they're SC heads...

He's running SC heads, either 1978 or 1979 large port.

[sand_man]

Originally Posted by equality72521

He's running SC heads, either 1978 or 1979 large port.

Yeah, that's right...

[JBL930]

Turbo heads are made from RR350 alloy (it'll be printed underneath the head somewhere), the carrera heads are not. RR350 was developed by Rolls Royce (hence the RR) for cylinder heads in the last aircooled combat aeroplane engines. It's about as durable an alloy for heat that exists for the job, there are other ubber ubber expensive alloys that are equal or slightly better but RR350 is about as good as it gets, Porsche didn’t use it for fun, and that’s on a stock low boost engine! Make your own conclusion..........

[billjam]

Originally Posted by JBL930

Turbo heads are made from RR350 alloy (it'll be printed underneath the head somewhere), ...

Correct ...


Mike, I have also been looking at heads lately and after some input on other threads by Rarly and others, it seems that going with larger ports is NOT the way to go on our charged engines. The clear consensus is that maintaining air velocity through the inlet ports is important for retaining low end power.
Driveability is important to me so I don't want to throw away low end power just to get more power at the top end (can always get more boost!).
I haven't figured out to link to it, but I suggest you look at some of the posts on my recent thread related to "stupid inlet spacers" as there might be some useful info there for you.

Consequently, I have decided to stick with standard inlet spacers (32mm ID) and inlet port size. What I have done though is smooth out the various bumps in the ports and open them up a little under the valves to ease airflow in and out of the head. See the befores and afters below.
Still to be done is some polishing of the exhaust ports and the combustion chambers, but that is next weekend's task.

[MikeHall]

That info is good enough for me. Thanks for pointing out the good things about the 930 heads.

Mike

[juicersr]

Craig is a big believer in the big port 78/79 heads. As for advantages over the Carrera heads, not sure, there are plenty of big HP engines out there (Protomotive, WydRyd, etc. ) using carrera heads. My engine was built starting with a blank sheet by a reputable builder in Cali, he choose Carrera heads and Manifold over the 78/79 heads. Regardless, the consensus is that the stock 930 heads suck big time.

[juicersr]

Previous thread

The ideal Turbo head? 934? 935? Stock Turbo?

[JBL930]

I think saying 930 heads suck big time is nonsense, they may require more machine work than a carrera head to mate up with the carrera intake manifold, or they may need considerable porting to match your performance goals etc etc, but it is FACT that the carrera head is made from an inferior alloy. Carrera heads may well be ok for a street car that sees very little WOT, but for a properly built engine put through its paces on the track they simply wouldn't last.

[NathanUK]

Personally I wouldn't worry at all about using 3.2 heads as it always seems to be the P's & C's that fail or the heads lift before there is any failure of the heads material.

If you are not on a budget then get your heads how you want them and enjoy their superior material.
If you are on a budget sell your perfect 930 heads and buy some 3.2 heads if you are going to fit a 3.2 manifold.

[930gt-40r]

Well the big problem that I have seen with the 3.2 heads (Ive seen it dont mean it will happen to everyone) is that the twin plug conversions crack when introduced to too much heat where the 930 versions handle it better. The stock 930 head dont have to suck, they serve their purpose from the factory. The reason being is that the stock style turbos didnt throw off that much volume, therefor to keep the range of useable power as broad as possible, porsche used smaller intake ports to keep the velocity up. I went the route of doing all of the machine work to the 930 heads and they seem to work good. I cant complain about them.

[Craig 930 RS]

Hello to everyone, been out of town for a bit -

Your best bet are the 78/79 big port heads. Why?
Why would I want big ports on a 930 when the tiny ports work so well on an early turbo?
Why would I want to forego the toough 930 alloy for the aluminum SC heads?

Modern turbochargers rely more on good ol' volume than velocity.
Turbocharger design as well as efficiency has greatly changed over the years, and, with everything else optimized, larger port SC heads make about a 15-20 HP difference.

SC heads only offer a theoretical disadvantage over the tougher alloy 930 heads. Time has proven that there is zero problems with SC - or for that matter - Carrera heads. Structurally and functionally they look like new at rebuild time, ask me how I know -

For me it just makes easy sense to sell the 930 heads at rebuild time, buy SC heads and rebuild those.
You are out virtually no additional moneys, and get additional performance for no additional dollar outlay.

[Craig 930 RS]

Old post, gives you an idea as to cost:
78-79 911SC large port heads

[930gt-40r]

Craig, I think the real disadvantage comes when you twin-plug them (which I cant remember whether you have them or not) but what got me away from 3.2's or SC's was when I saw a set of 3.2's crack through the second plug tap to the exhaust valve seat. The machine shop says that the alloy is the last defense against cracks in this area. There is also the idea of going with 12mm plugs and I have now seen someone with 10 mm motorcycle plugs.

[Craig 930 RS]

Haven't heard that. Mine are TP, don't forsee any problems whatsoever -
Contact Steve Weiner - he's the gu of ru regarding my setup and this stuff in general.

[Akila]

Craig sold me on this option, but I am sooo easy! I am having a set machined as we speak. Polished & 3 angle cut. By the way Craig, there was someone looking for some RUF's on Renn, if you havent sold those yet.

[WERK I]

Originally Posted by Craig 930 RS

................Modern turbochargers rely more on good ol' volume than velocity........

Craig, I see you have been rewriting the basic laws of physics......again.

If you are going to twin plug the heads, do use the smaller spark plugs. If you got 930 heads, use them. Just have the ports cleaned up, matched up and flowed.

If any work should be done on them, the exhaust port can be opened up a little so there is no bottle-necks to the turbocharger.