Difference between 901/02 and 901/16 heads?

TargaFlorio · 07-28-2006, 03:59 PM

Hi guys,

Could someone tell me the difference between a 1968 911S and 1968 911T (EU model) head?

901/02 had
1991cc
42mm/38mm valves
36mm/35mm port size
CR 9.8:1
160hp

901/16 had
1991cc
42mm/38mm valves
32mm/32mm port size
CR 8.6:1
110hp

Obviously, the S had bigger ports but they both have the same valve size. Is the rest of the cylinder head the same? Was 50 hp bump achieved by 'simply' using different cams, pistons, crank and re-jetted carbs?

Cheers,
n.

klaucke · 07-28-2006, 05:04 PM

I'm not sure what the head's CC at (i.e. their volume), but according to Peter Morgan Original Porsche 911 , higher piston crowns accounted for the increased compression. I just wanted to note that it is not necessarily the head. Of course his text lists the valve and port sizes as the same between S and T, so be weary of information from this source.

Grady Clay · 07-29-2006, 09:06 AM

Nicholas,

Welcome to the Forum. You will find lots of help here. How about a picture of your car?

What is your goal?
Do you want to use the “S” heads on your “T”? Do you want to convert your T to an S? There are some even better ways to go depending on what you want.

I’m 99% sure the heads are identical except for port size. The most important feature is the combustion chamber volume and that is the same.

You are correct; the additional power comes from compression ratio, cam profile, port size and carburetor venturi size. The “S” crankshaft is more robust (forged & nitrated) but that actually costs some power. The S gives up some performance at low rpm in exchange for the great high rpm power.

Of course there are many other subtle differences between a ’67 –’68 911S 901/02 and a ’69 911T 901/16. I found some other differences with the 901/13 911T in ’68.

BTW, I really like your art. I have a fairly complete collection of Factory posters, ‘50s and later.

Best,
Grady

TargaFlorio · 07-30-2006, 11:32 PM

Hi Grady,

I'm still in the process of doing 'homework' about the 2.0 911 engines.

I think the 901/13 was the 911T engine for Sportomatics.

I also came a cross the 901/26 engine which was used in the 1970 914/6 Rally cars:
1991cc
40mm Webers
I 42, E 38 Valves
I 32, E 32 Ports
Same valve timing as 901/02
9.9:1 CR
180hp

Here are the specs for the 901/30 engine (the 911 Rally car for 1967/68 season)
1991cc
46mm Webers
I 39, E 35 Valves
I 32, E 32 Ports
Same valve timing as 901/02
9.8:1 CR
150hp

Naturally those were race engines that weren't built to be as tractable as a street engines and longevity wasn't really an issue.

I think it's interesting to see how Porsche has all these different variations on the same theme.

To answer your question: I guess I'm still deciding about what to do with a 1968 911T (EU version since there was no US 911T in 1968). I don't want to just up-grade a 'T' to 'S' specs. I have a personal preference for the 911T with the 'Rally Kit' that Porsche used to offer. I think it consisted of more aggressive cams, up-rated pistons (to raise the CR) and re-jetted carbs and a dual muffler. I think it put out about 160hp.

BTW, thanks for your kind words about my paintings. I just finished a commission for the Porsche Club 911T Registry (to see the 'new' 911T.org site click here http://www.911t.org )

Cheers,
Nick.

Grady Clay · 07-31-2006, 05:47 AM

Nick,

You are correct 901/03 not 901/13 (Sportomatic). This is why I like this Forum so much. It is self correcting!

I assume you have Bruce Anderson’s book and the two early 911 Spec Books.

With some careful research and a lot of looking, I’ll bet you can find the pieces to build something like a 901/30 ’67-’68 rally engine S/N 488xxxx. You would want heads from a 901/02 with ’68 casting dates. The Mahle 9.9:1 CR forged pistons & cylinders are out there somewhere. The 46IDA3C carburetors are available. The tall magnesium intakes will be a challenge. The 901/02 911S cams are easy. Twin plugs are now doable with the Jag cap. Using the cast steel “T” crankshaft will gain high rpm power and is appropriate.

This is basically a ’68 911R engine with milder cams. Fun stuff.

Of course you can build a 2.8 12.5:1 that appears exactly the same. HeHe.

Best,
Grady

TargaFlorio · 07-31-2006, 09:32 AM

Grady,

I've got a bunch of Porsche 911 books and a friend of mine in Europe (who also wrote a book on the Carrera Speedster) sent me some Spec sheets that he obtained from Porsche Werk.

I might stick to the 40mm Webers, the 46 IDA's may prove to be a bit much on the street.

Could you tell me about the twin-spark Jag cap? I've looked into twin-ignition systems from Carquip and Supertec. They employ a custom made distributor (like the original Marelli and Bosch) that has a 12 plug cap for the wires.

Cheers,
Nick.