78 SC cis on a 2.7 motor

[carrera1975]

I just put in a complete rebuilt (jerry woods) 1978 3.0 ( 210 bench hp) in my 75 carrera,

964 cams
1981 p/c
ssi
2 into 2 sport muffler

I am now going add weber carbs. my 1978 CIS is in great shape as well as my 2.7, can I mate up my 78 cis on to my 2.7?

Thanks, this my first post here on pelican

[sammyg2]

Yes, you could. It would even run, but I doubt it would run right. CIS is tuned for a certain engine and takes into consideration compression ratio, displacement, cam lift and timing, and ignition timing.
I have never done this swap but I would bet your next paycheck that it would not meter the mixture properly and you would end up with improper metering and flat spots.
If you had a later version of the CIS with lambda it would self-adjust to overcome some of these problems.

[Jim Williams]

Why would you want to put the 3.0 CIS on the 2.7? My guess would be that the performance would be less.

Physically, you can mount the 3.0 CIS on a 2.7, but the components aren't matched. You may find that it seems to run "OK", but the 3.0 throttle body diameter is larger than the 2.7, and the air flow sensor venturi of the 3.0 is smaller than the 2.7. So it should be obvious that it really doesn't match up. The fuel distributors are also different, and the intake runners of the 78 3.0 are larger. It might take a dyno run with both CIS to discover the places on the torque curve where the 3.0 falls off.

[klaucke]

Some WUR tuning (i.e. with an adjustable WUR) could likely get you better than the stock 3.0 system, but still, it wouldn't be optimal. That said, its not like CIS meters that well, so you might be able to get the 2.7 to run pretty good. Also, you could to an EFI conversion like the T-Bitz kit, which would alleviate a lot of the idiosyncracies b/w swapping systems, although you might want to match the ports and intake runners.

[JP911]

I'm interested in your CIS if you decide to sell it. PM me if you're open to offers.
-Jon

[dd74]

Carrera 1975 - You are talking about two engines, correct?

I agree with the others: I'm not so sure this will work. Given the difference in the 2.7 distributor, and other differences - ignition (I think) for one, this may be a fruitless endeavor. With that said, I do know of practices where older CIS from '78-'79 has been adapted to later CIS engines, but who knows if that's even worth it, as several people have stated the CIS on '80-'83 engines are more optimal for the 3.0's cam profile and the engine's overall ability to breathe. In short, the smaller diameter runners in the CIS system seem to be the better ones.

Whatever the case, TBitz has a nice setup that works on a 2.7. And Webers would be a great addition as they add some power, have better fuel response and are lighter in weight than CIS.

210 hp out of a CIS engine is respectable as is. I'd sell the '78 CIS, and the 2.7, then save up for a better induction system. Maybe the money from both items would already cover Webers or a TBitz system.

Good luck!

[steand]

Or you could by individual Throttle bodies, and EFI system (tbitz or other) for max performance, and tuneability.

[Dan Mc Intyre]

Here is an idea for a hot 2.7 with a 3.0 CIS system I got from TRE Cup. He seems to think it'll work.

here is a recipe for inexpensive build up IF you have some skills at doing the motor yourself:
get a set of JE higher compression p/cs' no more than 10.5 :1
get your ignition distributor recurved to RS specs
get a 78-79 CIS complete injection system (from a carb conversion?)
get a set of SSI's or headerswith twin outlet exhaust
get your cams reground to 964 spec or get the 964 cams with towers
port your heads to 38 mm intake- leave the exhaust alone
when setting up cam timing- go for as much advance in the spec range as possible
you will have a motor that puts out a true 200 hp coupled with everyday reliability. So in the end euro SC performance from a lighter car at low $$ investment. And it will look "stock" to the average Porsche guy

Dan

Ok, lets talk 2.7

[carrera1975]

Thanks everyone who replied, This site is excellent.

I rebuilt my 78CIS it a shame to remove it, but the added 20hp will be worth it. I purchased a set of weber carbs ( new in box) manifold, linkage and air cleaners for $1,200.

I will think about my options with my org. 2.7.

One more question, should I keep my 2.7 as is because it is cardex'd to my VIN Number. 9115400294

I am not planning on selling the car anytime soon but I have kept all the org. parts that I have upgraded. Someday someone may want to have the 165 hp version again.

Thanks again
Carrera1975

[dd74]

Originally posted by carrera1975
One more question, should I keep my 2.7 as is because it is cardex'd to my VIN Number. 9115400294

I am not planning on selling the car anytime soon but I have kept all the org. parts that I have upgraded. Someday someone may want to have the 165 hp version again.

Thanks again
Carrera1975

If you can swing it, I'd keep the engine. Sometimes I wish I still had my old 2.7...if only just to look at...

[ckissick]

Even though a '75 is not in the same collectible class as a '73 or earlier, it may become somewhat collectible in a few years. Of course, a stock '75 2.7 is the about the worst engine Porsche ever built, but the problems are well known and can be remedied. I'd keep it.

A spare engine in the garage makes you look cool to your friends. I know, because I have a 2.7 sitting in my garage. My '70 has a '78 3.0 with Webers, and I highly recommend the setup.

[carrera1975]

Ckissick

What kind of hp are you getting with your 78 3.0 weber set up?

I have 964 cams, SSi, Dansk sport muffler.

thanks,
Carrera1975

[ckissick]

I have 20/21 cams and Bursch headers. Dave at TRE, who put in the cams but never ran the engine (I shipped it to him) estimates it might make 250 hp at the flywheel. Jerry Woods says that estimate might be only slightly high. Whatever it is, at 2110 pounds, it's fast.

[TRE Cup]

Keep your original motor- these cars are starting to enjoy more collectibility as newer ones become so generic

[dd74]

Originally posted by ckissick
I have 20/21 cams and Bursch headers. Dave at TRE, who put in the cams but never ran the engine (I shipped it to him) estimates it might make 250 hp at the flywheel. Jerry Woods says that estimate might be only slightly high. Whatever it is, at 2110 pounds, it's fast.

So you have CIS pistons, 20/21 cams, headers, Webers and this puts you at an est. 250 horsepower?

Jeez Louise - very nice...