3.1 SC engine?
 

So,after purchasing this car about 3 weeks ago, I went to take a pic of the engine code and # last night at the recommendation of a fellow Pelican . Upon doing this I discovered something very interesting... Group911 showed me an article that has me pining for more information. I have scoured the web and Pelican forums but everything seems to have dropped off a couple years ago. Has anyone found anything more about these engines? Are they as rare as previously believed? My stamp is a little different than Jim Williams', is it still the real deal? Have anymore been found? Still believed to be limited to 100-300?

http://forums.pelicanparts.com/uploa...1333944440.jpg
http://forums.pelicanparts.com/uploa...1333944461.jpg

One of the Porsche magazines had an article on the 3.1L a couple of years ago. I will look through my stacks and see if I can find the article.

I believe they are also identifiable by the lack of cooling fins on the skyward sides of the cylinders... like the turbo cylinders. The stamp looks like the one in the magazine article I read.

Tsunamiboy,
Was it Excellence?

78SCRSMAN,
Do you remember which magazine?

Yes , 3.1 !!!


Very rare engine and very powerful.

Excellence :: Point One : The Forgotten 911 SC-L 3.1

It was in Excellence (A Magazine About Porsche Cars) Might I suggest you visit a newsstand... soon!

78SCRSMAN,
I've seen that article online but I did not see any pictures of the markings? Were there additional pics in the actual magazine?


DonnvWarner,
Did you post pics or something? it's just showing up as Xs to me.

It's value is reduced quite a bit in its current state. You've got some work ahead of you to bring it back to originality. Do the car and engine match? Terrific find though...

KNS- has anyone even determined a value on these? I was considering a 3.2 manifold as opposed to original CIS. Given the obscurity and apparent lack of knowledge on these engines, do we know how much of a difference it would make?

The 3.1 was a clever way for Porsche to increase displacement w/out needing to manufacture all revised pistons and cylinders. They used the 97mm 930 cylinders and had special 9.5:1 pistons made. You couldn't use the 930 pistons because of their low compression and also the 930 pistons use a larger wrist pin, which would mean the SC rods would have to be rebushed to 23mm in the small end.

As rare as the 3.1 may be, the 3.2 short stroke has been more widely accepted due to its "overlap" with the 3.2-3.4 Carrera upgrade. They both use the same cylinders and piston diameters, with the difference in the pistons being the compression height and pin diameters.

Because most of these cars are in Europe, you'd have to do some detective work to see what these cars are trading for over there. It's greatest value will be as a complete and original engine in the car it was sold with.

KNS,
Understood. Mine is not it the original car. It is an '80 engine in a '79 US SC.

All the listings and info I'm come across from Europe have either been deleted or are in German. Anyone know German and interested in some research? I'm really surprised the research seemed to die a couple years ago.( On Pelican at least) I haven't checked out any of the other forums yet.

It would, however, stand to reason that the 3.1s might be a bit more valuable in the US market since their are obviously very few that made it over the ditch. With a speculated 100-300 in the world and probably less that 10% of that in the US, who knows... I didn't really purchase this car as a collector but more of something fun for the weekends.. scratching my head at what to do now..

Put the engine back to a condition that's as close to what it was originally as you can. You may not find all of the special CIS parts but others could be made to work.

I'd get rid of the yellow paint on things that weren't originally painted that color, but that's just me.

I'd go through the rest of the car and make it 100% too, as I'm sure you'll find some stuff that's less than optimum. If I remember correctly, it has later 964 style wheels on it. I'd ditch those for something lighter. I'd also consider wheels with an offset such that you'd be able to get rid of the spacers that are probably there.

I'd also take a bit of weight out of the car, deleting things like the A/C, rear seats and anything else that I didn't need for weekend fun use.

JR

Here's the thing. Since I'm starting from scratch on the intake my plan was to upgrade to the 3.2 and EFI. This is never going to be a concours car and the car is not original from the factory with the engine. Knowing more about these engines and if there is any value in taking the time and money to put back to as original as possible will play a big part. I'd rather not have CIS if I don't have to. Unfortunately, in the 6 or so years of availably documented existance in the US it doesn't look like any has ever gotten very far or confirmed much.. most is just speculation. It's amazing that these are potentially very rare yet the information and knowledge is next to nothing..

There's really nothing all that wrong with CIS, if it's tuned properly. Most complaints about CIS come from guys that have systems that are a long ways from working properly. I think that you'd have better luck going down that road than trying to adapt an EFI system to an engine not designed for it. Tuning EFI is harder. Whatever you do, I'd avoid aftermarket EFI.

It's your car, so you get to choose what you do. I'm just offering my opinion, based on what I've owned and driven over the last 30 years. I've usually prefered a well-tuned, near stock car to those that have been heavily modified. Even though there's a lot that's not stock about your car, it still is not too far down the road, so...

There's not a lot of information about the engine that you appear to have, since nothing much was officially put on paper and the people that were involved aren't talking. Still, I'd take that engine over a normal 3.0 or 3.2 in a heartbeat. It's unique enough that I think it ought to be saved.

Have fun,
JR

Dang, can't find the issue now. I just remember seeing that 3.1 stamp in a picture somewhere. Perhaps here.

Someone in a previous post said to try and put it back to original... Maybe I missed something but is it not original as is? (the engine I mean) other than the pistons and cylinders the only other thing they may have changed was the fuel distributor. I would say check the P/N on the fuel distributor and get under that thing to see if the 97mm cylinders are indeed in place.

Also someone mentioned not as much value if the car doesn't match the engine. In this case, there is likely no way to be certain as it was a dealer option. Obviously this car didn't come with this engine but if it had, there would be no way of knowing for sure unless there was some supporting documents.

If it is indeed a true 3.1 and you just want a fun car to drive, I might consider selling the engine to a collector and just buying another engine... perhaps a 3.2 or whatever. You might be able to end up with a fresh (rebuilt) engine.

78SCRSMAN,
Unfortunately the CIS and 3.0 manifold was removed and replaced with, of all things, a Holley. So the fuel distributer etc is missing. I have considered what you are saying so that is a definite possibility as well. I love the history and rarity of it but not sure if I want to take on the commitment that this engine deserves.

78SCRSMAN,
I'm sure this is an absolute noob question but, how would I go about checking the pistons?