3.6 heads
 

What are the significant differences in the 3.6 heads from 89 to 98. Dimensions, performance? Thank you, Bob

Here's pics comparing 964 and 993 head. 993 head is one with valves. From a dimensional standpoint the complete intake port on the 993 head is much bigger (kind of hard to see in pic). ...don't mind flowers in the background. :-)

http://forums.pelicanparts.com/uploa...1644016723.jpg

http://forums.pelicanparts.com/uploa...1644016723.jpg

http://forums.pelicanparts.com/uploa...1644016723.jpg

http://forums.pelicanparts.com/uploa...1644016723.jpg

Yes, you can see the diameter difference and it doesn't take much of increase there to make a considerable volume increase. Looks to be a late 964 head. Thanks for the response and the flowers are a nice touch. Bob

There are early and late 993 heads. The late heads have larger valves. All 993 heads are made out a better aluminum than the 964 heads.

Bob - I have blank 964 and 993 heads. What dims do you want? The 993 heads in pic have 51.5 / 43.5 valves.

Those appear to be RoW heads in both instances, lacking SAI

here's the SAI port for US engines


http://forums.pelicanparts.com/uploa...1644279956.jpg

note that the 993 heads have all 4 stud holes for both early and late pattern headers, 964 only has the early pattern
http://forums.pelicanparts.com/uploa...1644016723.jpg

993 heads are cast w. RR530 alloy as was used in 9430 heads, 964 is a baser alloy w/ less heat resistance, though 993 heads do appear to be more prone to cracking unless reinforcement welding is done

http://forums.pelicanparts.com/uploa...1644280213.jpg

964 ports are all 41.5/38 unless you have the 964 3.8RS which are46/42
964 valves are all 49/42.5 except 3.8RS which are 51.5/443.5

993 nvr ('94-95) ports are 43/39, vram('96-98) are 43/39, RS is 46/42, RSR& Cup is 46/42
valves are nvram 49/42.5, vram 50/43.5, RS is 51.5/43.5, RSR & cup is 51.5/43.5

964 heads have 9mm valves and 993 have 8mm.

Do 993 heads also have the ceramic inserts in the exh ports?

Yep on the ceramics

Xtreme heads are the ticket!!

+1

xtreme heads
 

So is a Lamborghini, but both are beyond my means. To quote Smokey Yunick, '' there are 2 types of racing, expensive and then VERY expensive.''

I like the other line. "What part of racing Porsches did you think was going to be cheap? The racing part or the Porsche part?"

I believe Bill V shared this document years ago and I saved it to my google drive. It's got some interesting information

https://drive.google.com/file/d/0B7Bo-8bAu9G9NUY3YUJQcjFJTW8/view?usp=sharing&resourcekey=0-wMe-9TYRISmq7Hi3nqVJpw

993 has the bigger intake part like the guys mentioned- increased from 41.5mm to 43mm. Also the cooling fins were made thinner to increase cooling (more air flow) and also made the head nuts and the spark plug connectors thinner to let more air through the cooling space?

Also notice that for whatever reason, the studs in the head were eliminated for the mounting of the camshaft housing and instead the 993 heads use socket head screws.

There are two types of economy when building competition engines, false and real. One has you buying something less expensive up front. The other, has you buying something more expensive up front that will save you money and headaches down the road. Xtreme heads are the later.

You should buy what you think you should buy. I just put an option out there…

My understanding is that the problem with the stock castings is they crack when the horsepower approaches 400 hp in racing applications. Xtreme heads are pricy but a good investment if you’re looking for performance and longevity.

I was originally planning to get 993 heads redone by Xtreme but Bill talked me into his heads because he thought it would be much better and so glad I did.

And maybe buying his heads you will get them faster? He has had my 930 castings for a full CNC port/ big valve, new seat etc. for 8 months. Supposed to be done soon..... we will see.

Between Gunterworks and Singer and everyone else, I think he pretty darn busy these days.

My heads were delayed too but Bill said it was a supply chain issue with the valves