930 convert to 3.2 heads?

[porschadoc05]

Hi all, curious to know if late 3.2 heads would be a nice upgrade on a 930 build?

Thanks in advance for any guidance.

[Ken911]

930 heads are made from a different alloy RR350. It has a higher ability to withstand heat than the 3.2 heads.

[jpnovak]

3.2 heads can handle the heat no problem.

IMO, there is no point to do this unless you are chasing more power as part of an overall plan to increase induction and exhaust flow. Your engine is an air pump and you must optimize all aspects of the in/out flow to make it most efficient.

[K24madness]

I’d stick with the RR350 930 head and have em ported.

[T77911S]

do the bigger ports increase turbo lag?

im trying to reduce and bought another turbo that spools faster, but would like bigger ports but don't want to go backwards.....too much

[porschadoc05]

Thank you all for the input. Decision made.

[RarlyL8]

do the bigger ports increase turbo lag?

Sizing needs to match other aspects of your build/goals. SC/Carrera heads are a nice bump for the 930 as they are not so large as to significantly influence lag but larger than the smog ports of the 930. For optimal reduction of lag the port needs to be large enough to support your power goals but no larger. Cams need to focus on torque, such as the SC grind. Header design is critical, the primaries need to be no more than 1mm larger than the port (laminar flow) and reduce volume by the time they reach the turbo (velocity). Equal length is best if possible, at the correct pulse harmony for peak torque/power. When the system is tuned everything works together.

[philip j]

3.2 heads are a awesome upgrade... all depends on your goals. Leave as they are, or the sky is the limit...

[nocarrier]

Are you using a 3.2 intake manifold? The gasket sealing surface is a different shape.

[spuggy]

Originally Posted by K24madness

I’d stick with the RR350 930 head and have em ported.

That's what I did - although plenty have run 3.2 heads at very high power levels without issue.

On the topic of temperature, I find it interesting that Motec says my head temps are much, much, higher after the car has idled for a relatively short period (5-10 minutes) than they get at any other time....

[Tippy]

The 3.2 heads are a huge upgrade in my book.

The 3.2 heads will take the heat (boosted mine to 1.6 bar). This is getting to be an urban myth about the heads not taking the temps.

[Ollies930]

All the 935 heads I have seen (pictures on internet) have been of regular alloy, not RR350. Those heads survived for 24 hours at 600-750 hp. Porsche probably decided on the RR350 alloy on Turbos, expecting their European customers to be cruising on the Autobahn or the like at very high speed for extended periods of time. The RR350 alloy probably gave them the added safety margin needed to let their cars run for 75,000 miles or more without needing to rebuild the engines more frequently, which would be unacceptable. This is of course just me second guessing why the factory did what they did.

[spuggy]

Originally Posted by Ollies930

All the 935 heads I have seen (pictures on internet) have been of regular alloy, not RR350. Those heads survived for 24 hours at 600-750 hp. Porsche probably decided on the RR350 alloy on Turbos, expecting their European customers to be cruising on the Autobahn or the like at very high speed for extended periods of time. The RR350 alloy probably gave them the added safety margin needed to let their cars run for 75,000 miles or more without needing to rebuild the engines more frequently, which would be unacceptable. This is of course just me second guessing why the factory did what they did.

Ah, this again - the topic that just keeps on giving. (not being sarcastic; I learn something everytime I google stuff on this)

The 935 heads I've seen photos of are all marked as using Y-alloy (Yttrium) heads, like the 2.4S (but not the T, E etc) heads (Y-alloy heads? Your 2.4S has 'em).

Seems from that thread that all heads from the 2.7S up to the 3.2 (and including SC) were y-alloy heads - except the 3.3 turbos.

As far as the difference between RR350 and "regular" heads, to quote myself from this thread The ideal Turbo head? 934? 935? Stock Turbo?

If the alloy used in standard air-cooled heads is really AMS4220 as Bill V suspects in the thread I linked in earlier, then the difference in rating betweem RR350 (aka AMS225B) and AMS4220D is the difference between 600F and 400F according to the specification:

(link mentioned was in this thread Truth or Rumor: 930 vs. 3.2 heads - and when I wrote that, I didn't know that y-alloy even existed.)

A delta of 200F is a pretty substantial difference - 50% hotter again. Read the spec for RR350 (its on wiki/in those threads); unlike y-alloy (which was developed specifically for aircooled aircraft cylinder heads), RR350 was developed for bearing housings in jet turbine engines, IIRC..

Although it was not unknown for aircraft manufacturers to use RR350 for their cylinder heads either...

However, the fact that guys are running well over 600HP with 3.2 heads with no issues would seem to indicate that the heads just don't get that hot.

Composition of the head alloy just doesn't seem to be an issue as y-alloy is fine- heck, the factory used it for the 935....

So the right thing to do is get your port sizes bigger/right-sized, you can probably use any head you like - YMMV. Others have, w/ no issues...

As far as second-guessing what the factory did, and why, that's always fun, right?

The 76-77 3,0 930s also didn't use RR350 heads (I did not know that until just now), only the 3.3 turbos (which I presume includes the 965, as there seemed to be only incremental changes to that).

Even more interestingly, the factory also used RR350 for the 993 GT2, GT2 EVO and 3.6 turbos, (even when the bean counters were circled), despite RR350 being expensive (proprietary tech licensed from external supplier) and more difficult to machine...

You could argue for the 930 that this was early days for turbo street cars, and the factory just played it safe initially; widely known that the 930 was originally a homologation special with an intended run of 400 cars for sale to the public so that the factory could go racing in Group 4 (and according to Starke, factory was worried they would struggle to sell even that many, and believed that almost all of the cars would be bought by race/club drivers and live as track rats- rather than being, as they were, widely bought by doctors, dentists, athletes, lawyers, gold medallion man etc. and driven on the street)

And some things about the 930 - like the very cold plugs - were apparently dictated by EPA/DOT approval; changing them after the fact would have necessitated re-testing - so they just never did.

However; they almost certainly had to re-test for later cars - like the 993s; which lost the cold plugs - but kept the RR350.

Why? Darned if I know - it must have seemed worth it to them at the time...