Fabio421

I thought this might be of interest to some of you. I have three different heads that I will show here. The size and shape of the combustion chamber may be of interest to some of you. I also measured the exhaust port sizes. It's interesting to note that the two 928 heads have stainless steel inserts in the exhaust ports while the 944 Turbo has what looks to be ceramic liners in the exaust ports.

#1 1980 US low compression head. This head was machined to accept the larger "Euro S" sized valves. The exhaust valves are sodium filled and came from a 951. This set of heads was built for a turbo on gasoline project. The idea was that the larger valves should flow better but not have the higher compression ratio of the Euro S heads. It should net about 8.5:1 on a 4.5 liter bottom end and a bit higher on the 4.7 liter. I may not use these heads now because I've decided to run E85 ethanol. E85 doesn't heat up the valves or engine nearly as much so the soduim filled valves are unecessary. The E85 also doesn't need the lowered C:R becasue of its much higher detonation threshold.

#2: 928 Euro S head

#3 944 Turbo Head

IcemanG17

great data.....I was reading a 944 article the other day, I think at Lindsey racing & they were saying that stock 2V 944 turbos flow MORE out the exhaust than the intake....I also think the exhaust has a stainless steel (or something similar) liner?

Fabio421

I think this info deserves to be in this thread too.

U-928

I'm guessing not all 2V head have the liners. I know for sure my 4.7L US heads don't. Sorry I don't have the pre-ported opening diameter.

danglerb

US 1980 heads are 4.5L motors.

Fabio421

What is the purpose of the notch cast into the combustion chamber on the 928 heads? I'm talking bout the notch that is between the valves and directly below the spark plug hole. Any idea?

BRB-83-911SC

Interesting, those notches. My Euro S heads did not have them (early 84, 928.104.348 3R). The area around the plug hole looks different too. 40mm exhaust valve, 45mm intake valve. Here is a pic before cleanup. They have since been cleaned and installed, but apparently I did not get any post cleanup pics.

Fabio421

Is it possible for you to cc your heads? That combustion chamber you posted looks larger than the Euro S head I show above. As far as I know, it shouldn't be. Also, what is the part number on the heads.

Thanks

GlenL

My Euro S heads, which I've had off 5 or 6 times, don't have that notches either.

After you mentioned it I went back to those pics. Whatever could that feature be for? Last second attempt to increase head CC?

U-928

He posted the part number right in the post you quoted. And seeing as they are installed, I'm guessing cc-ing them is out of the question.

Any idea why when Porsche went from the 4.5L to the 4.7L's they ditched the inserts in the ports?

Fabio421

Doh!! I didn't see that. I guess I didn't fully absorb his post. Sorry about that.

Do you agree that the combustion chamber looks larger and is shaped differently?

U-928

I figured you just didn't see it.

I don't know about larger, that's hard to tell. Don't know what the volume of that little missing wedge is on your Euro S heads.

Could also be a little deceiving as Brians head surface isn't clean like yours. I think the carbon build up may be making it look more different then it actually is. That said though, I do think that the area around the intake valve comes up as "steeply", for lack of a better description.

Anyone else watching this thread have a similar head to Brians that could do a cc check?

Fabio421

The Euro S heads I posted above are p/n 928.104.348 2R. I just checked and I do have a set of p/n 928.104.348 3R heads that I can measure but it will be a little while. I have them on an engine thats on a stand. I'm using that engine to moch up my fuel system for my Megasquirt3x conversion. I should hopefully be able to pull them off and take a look at them in a couple weeks. I think I cc'd those heads at one point but I don't know what I did with the #'s. I'll look in my notes and see if I can find them.

I also have another set of 2R Euro S heads that I can pull off another engine this weekend and confirm that they are the same as the ones posted in the OP, although I wouldn't expect them to be any different.