911 Sc 3,1

[Hansv]

Hi there, Porschefans;

As a longtime Porschaholic (not an owner yet, but working on it) I'm a regular reader of this forum and it never fails to surprise me in showing an almost limitless knowledge of all things Porsche. For that reason I decided to turn to you guys & gals to help me in my quest for information. The subject of my curiosity is a rather obscure 911: the 1979 SC 3,1. This version, that was probably a sort of evolutionary step in the development of the later Carrera 3,2 is basically a hi-performance version of the 180hp-EuroSC. It's barrels are of the 97mm 3,3l Turbo-size, but feature a 9,5:1 compression ratio. Combined with a retuned CIS and a different exhaust system this resulted in 210hp at slightly higher revs plus a useful increase in torque. Interestingly the engines, of which 100 are rumoured to be built an sold in complete cars, were already equipped with hydraulic distribution chain tensioners.
A variation on this theme could be the performance kit the factory would install as an option on 180hp-Euro cars, of which some 1100 were supposedly sold.
Any information on this car or engine would be very welcome.
Some info can be found through these links, one in French, the other in errr, well English of some kind....
http://www.club911.net/article.php?sid=147&mode=thread&order=0#3l1
http://users.compaqnet.be/skyimages/porsche2/p911/SC/911sc31.html

[Jim Williams]

Hansv,

Well, you came to right place.......

I have one in my garage being rebuilt as I type this. Since I cannot trace the car's journey from the factory to me, I cannot verify that the engine as I bought it represents what the factory produced, but I believe that it does.

Since I don't read French, I have no idea what the the first link's description is telling us. I do recognize some of the numbers, like 97.

Since the second link is, I think, a Belgian site, a few words seem to have been invented by the author, but they seem to sort of make sense.

I bought the engine sight unseen, as a rebuilt 3.0 liter. It was not a 3.0, nor was it rebuilt. The seller had no idea what he was selling, and I of course, had no idea what I had bought when I opened the crate. When I related to him what I found when I uncrated the engine, he apparently thought I was making a lot of it up, and refused to hear any more. I wanted to send the engine back, but he would have none of it. At this point, I had never heard of a 3.1 liter engine, and thought I had bought some something put together with some leftover parts. There is more of the story, but it is not pertinent to your question.

I have taken a lot of photos of the engine as it came apart, and have more as it is going back together. I can post some of the photos if there is any interest. The engine number stamped on the case verifies the 3.1 configuration. I cc'ed the engine and calculated a 9.8 compression ratio. The actual numbers could be 9.5, but I feel pretty good about my number. The CIS components appear to be mostly stock for a '79 SC except for the Fuel Distributor, which has numbers on it I have never seen before, and I've seen a lot of CIS engines.

It came to me with the pressure-fed chain tensioners, but I assumed they had been added to the engine, as I was unaware that these tensioners were in exsistence 5 years before they appeared on the '84 cars.

The exhaust system on the engine as received appeared to be a severely rusted stock SC set of heat exchangers with no heater boxes. These promptly went into the trash heap.

Oh, and I can verify the 97 mm cylinders (with the higher compression pistons).

I have a performance graph which Mr. Adrian Streather (author of the SC book, The Essential Companion) sent me. He said that he heard rumors that Porsche produced such an engine but had no verification of it until I told him of the one I have. The HP curve does peak at 210.

I am putting the engine back together stock except for 964 cams which I hope will allow enough piston-to-valve clearance with the higher dome pistons. The cams in the engine were stock SC.


(Edited to correct some spelling errors)

[Kraftwerk]

this is better than that di vinnci code story, very cool!
Jim, does the engine have any numbers on it that distinguish it as a 3.1 rather than a 3.0?

[Jim Williams]

Here's the *3.1* stamp:



And here's the performance curves, courtesy of Adrian Streather:



The engine number is *6393858*.

[Jesset100]

More Pictures

[RarlyL8]

What a hoot!
I had never heard of a 3.1L until you told me that story a few months ago Jim. Now someone is asking about it? Just when I thought tech had died and been replaced by "show me your tires" threads. Pretty good first post there, I think we can skip the "why didn't you try the archives" jab for the noobs.

[island911]

Originally posted by Jesset100
More Pictures

+1

great stuff!

[Fishcop]

Fascinating!

[Kroggers]

Cool stuff. More pictures please.

[livi]

Amazing! A thrilling thread.

Be interesting to hear what the "old" guys around here know about it.

We need an informer in Stuttgart. Like an old janitor that has swept his broom along the corridors in Head Quarters since Butzi and the Boys.

[K-Jetronic]

...and here we have one for sale....

http://www.marktplaats.nl/index.php?url=http%3A//koopjes.marktplaats.nl/auto_s/porsche/33163303.html

[Hansv]

Hi there, Jim;

Now that's the kind of info I was hoping for. Great to find you have an actual 3,1! I'm not sure yours rolled off the assembly line with the hydraulic tensioners, because the 100 engines were sort of a testbed for them. Could be yours is a rare factory hi-po engine that did actually make it to the (EU)options list in 1979. I can imagine the tensioners having been replaced somewhere later in it's life. It is also kind of surprising to me that one of these gems made it to The Colonies. All I'd found out so far suggested them having been sold in Europe only. The complete cars (as seen in the French article) were never even sold through official channels and were to be serviced bij selected European dealerships only.
I'm trying to convince the editor of '911 & Porsche World', a British Porsche magazine, to do a feature on this Holy Grail and the extra data just might do the trick.
Thanks a lot and keep us posted!

[Hansv]

Hi there, K-Jet;

Spaarndam, eh? It's a small world....
That's the actual ad that made me start this search. I already posted some questions on www.porscheforum.nl about the same car and it's engine. On a German site I found another one, but that was already sold.
http://www.diezwei-sportwagen.de/Autos/scgruen/scgruen.htm

[javadog]

This is an interesting thread. For years, there has been information in some of the Porsche books about a 3.2 liter engine that the factory offered as an upgrade to owners of a new 911SC, starting in 1979. The story is that the work was offered through the factory repair department and included 98mm Mahle pistons and cylinders and a different fuel distributor. The displacement ended up as 3186 cc and the claimed power was 220hp.

I wonder if the facts reported in the books were slightly in error and the pistons used in this upgrade were really 97 mm? It seems odd that Porsche would offer two different upgrades that were so similar. Does anybody know of a car that got this upgrade (the 98mm one) at the factory?

JR

[Hansv]

Hi there, Javadog;

I've heard of these short-stroke 3,2's. As a result of European 180hp-SC-owners being disappointed in the performance of their cars (and to no surprise; it's predecessor Carrera 3,0 combined 200hp with a car weighing less) a lot of tuners jumped in and created faster versions using the 98mm Mahle pistons you mentioned. One of the best known in Europe was the Ruf SC/R, that was even built in a small series. It could very well be that the factory steered away from the experimental 3,1 with 97mm custom pistons with the 98's readily available, but I don't know if they actually ever offered these themselves as an option or a kit.

[Hansv]

Hi there, Javadog;

Enter this link, scroll down en you'll find a 3,2SC. No further info, so I don't know if it's a factory special, but it just might fit the bill.
http://www.flat6.com/projects.shtml

[Hansv]

Hi there, Porschefans;

After careful studying Morgan's Finest once again I
came up with two option codes that may give a clue;
M148: modified engine 930/66 and
M702: High-performance engine 930/66
but no further information is given.

[javadog]

A 930/66 is a 3.3 turbo engine for ROW cars from the mid-80's. I'd say that the 3.1 engines were probably built from a 930/03, 930/09 or 930/10.

JR

[Hansv]

Hi there, Javadog;

You're right; perhaps Morgan's "the Original 911" isn't such a bible after all....

[javadog]

I agree. He thinks the 930 got Motronic fuel injection in 1986. The pictures are nice, though.

JR