77 3.0 CIS, to carburate or not to carburate?

[jwakil]

I have a 1977 3.0L CIS engine in my car, no O2 sensor or cat. I've been thinking of going the carburetor route, for simplicity, less clutter in engine, and more performance. The CIS system is just too finicky in my opinion. Too many variables to get out of wack or try to keep in synch, too hard to diagnose, and takes up too much space. What are the opinions of CIS vs carburetor for those who have experience with both? What would be the cost of retrofitting a CIS with carburetor?

[Scott R]

It looks like you don't have emissions testing where you're at so carbs won't be a problem for you. The only thing you have to get used to is the cold start up. without chokes are any type of warm up regulation you have to that yourself.

[911st]

Carbs= crisper throttle response, 10 more hp but seem like more, lower MPG. Makes for a very fun car. New PMO carbs should be pretty trouble free. 911's with carbs had a manual throttle lever between the seets to help with warm up.

Should have a good header exhaust system to go with it and might want to look at recurving the distribuitor. About a $4k investment I think.

Webbers can take some work.

On the other hand, you could send your CIS Fuel Distribuitor and WUR out for a rebuild ( www.CISflowTech.com ), have the injectors cleaned and tested, and get your system in to to new shape for about $1k if you can do the work yourself and probably not have to mess with it again for years to come. Nothing wrong with a good running CIS system along with a good sport exhaust system.

[azasadny]

I switched my car from CIS to Webers several years ago. I bought the Webers here on the used parts board and all required hardware from other sources and I think it was $1600 by the time everything was purchased. Tab Tanner from Autobahn Garage in Findlay, OH installed everything, got them tuned up and that was in December 2006. They haven't been tuned since and run great! Nice exhaust sound, improved throttle response and much cleaner engine compartment. I recommend the conversion if your CIS is a mess because the cost to repair/replace the system can easily go higher than $1600, especially if the fuel distributor is bad, link mine was. I only drive the car during warm weather in MI, so they don't need to be adjusted.

[Laneco]

Had a 3.0 CIS that I drove for a couple of years. Put the engine in a different car and went with PMO carbs. I really don't think there is a better carburetor on the planet than PMO. Set 'em and forget 'em.

The catch is, you got to set them. If you go this route, buy the new linkage and have the carbs setup by someone who knows what they are doing. A freakin' monkey can get these to run, but you need a bit of black magic talent to get any multi-carb system perfect. I drove our car two years with the PMO's on. It ran just fine. Then had Guy's Porsche in SLO adjust them - holy smokes, it ran like a cat with a hot sake enema!!! There is the difference between a monkey (like Steve and I) and a talented professional...

Now about CIS. It gets an unfair rap. I've been driving CIS cars for years. With no vacuum leaks and sound parts, CIS starts easily and offers very good driveability (though compared to carbs, it feels a little flat footed). I think a healthy CIS system is probably as trouble free as brand new PMO carbs and a whole bunch less trouble than a set of 40 year old Webers. Well, unless Mr. Beeker has overhauled them - LOL! If this is a dedicated street car, honestly, I would stay with the CIS.

The Webers are not as nice on a street engine as PMO's. PMO's are really an extroardinary carburetor. Bear in mind if you buy them new, you'll spend well of 3K plus the tuning costs.

angela

[azasadny]

Angela makes some excellent points. My CIS was in terrible condition and multiple components were in need of replacement. I didn't have access to PMO's and found a very nice set of Webers that Tab rebuilt and tuned for me. I bought new linkage, rain hats, fuel pressure regulator and fuel pump. I sold many of the old CIS components and got back some of the $ I spent for the Weber conversion.

[jwakil]

Gunter, as my post says, the engine is a 1977 carrera 3.0 (Euro), with CIS. Body is actually an 83.

[topcarbon]

Zeniths here with the 2.7

[boyt911sc]

Originally Posted by jwakil

I have a 1977 3.0L CIS engine in my car, no O2 sensor or cat. I've been thinking of going the carburetor route, for simplicity, less clutter in engine, and more performance. The CIS system is just too finicky in my opinion. Too many variables to get out of wack or try to keep in synch, too hard to diagnose, and takes up too much space. What are the opinions of CIS vs carburetor for those who have experience with both? What would be the cost of retrofitting a CIS with carburetor?

jwakil,

If you are willing to spend that kind of money that was suggested to get a set of PMO's, I would sell the motor plus $$$ budgeted for PMO to buy a 3.2 motor in good working condition. Unless you really wanted a carburated engine. Good luck.

Tony

[RWebb]

carbs will be much more fun with just a set of SSIs on your car

to really get power and more fun, you need new pistons & cams - which means a lot more $$ to get that lot more fun

[lindy 911]

I think it depends on how you're going to drive it and what you expect. I have a 3.0 SC ('78) that has Weber 46s, headers, twin plug MSD, GE 60 cams and 10.5 : 1 pistons. I also stripped anything that wasn't essential like A/C, cruise control, spare tire, any wiring that wasn't absolutely necessary and so on. I think it's about 2250#s now and although I have not dynoed it I think it's running about 250 hp to 275 hp at the rear wheels. This car is scary fast.

I was also told about how finicky Webers can be but have not found that to be the case. There was some tuning to get them just right but nothing to terrible. I know I've gone a lot further than what you have asked, but I don't think you will regret the swap.

Lindy

[911st]

Not sure but the 77 3.0 I think is a special motor in that the case is different than on the SC's.

As such racers want as they can put a 66mm crank in them and spin them up to very hight rpms.

Might be able to sell it and put the money toward a 3.2, 3.3 turbo, or other motor.

[esotoracing]

EFI (other than originality or cuz you already have them, why even consider carbs or cis)

[Karaya]

I'm glad for all the positive replies for the PMOs as I also am going the PMO on the 3.0 route. Mine are coming soon and I can't wait to get things going although my car is still receiving painting and body work, I've got the engine at home and doing that myself.

[Gunter]

Originally Posted by jwakil

Gunter, as my post says, the engine is a 1977 carrera 3.0 (Euro), with CIS. Body is actually an 83.

The post didn't say Carrera or Euro.

Interesting engine to get an extra 30-40 horses without too much trouble and not go overboard with $$. (And no carbs)

Good luck.

[jwakil]

I didn't think the cost would be quite as high ($3-4k), although I really like the clean engine bays of the carburetor engines. From the posts it sounds like the carburetors would need as much fine tuning and trouble shooting if not more than the CIS. I think I'm going to stick with my CIS and try to learn more about how to optimize it. Maybe I can trade up to a motronic later on.

[brads911sc]

Good choice. A better move might be the Bitz EFI kit if you want a lower cost solution. Alot of people swear by it. When you are ready to spend the bucks, do PMO ITB with EFI not Carbs. Just my .02.

[BReyes]

Jwakil,

It sounds like it may benefit from service by a Porsche technician who is CIS expert. He may have to put in some serious hours but it may be worth it. You say you have "sport exhaust", possibly known as SSI. Then it has potential to be a great lil street car.

At what point would you normally shift into higher gears? Ever any fancy foot work? That is where your skills may input. You know CIS can be kept in the revs? Could some weight reduction help you also? Does your muffler flow well? Your lil 3.0 should start right up, run strong up on to the power curve, right foot, heel, toe, etc for that grin on your face.

CIS is good if it checks out and you get drive it every so often.

Regards,

[Bmxrams80sc]

switched to carbs and im never going back! Gives the car a more lively feel. I never have trouble with cold starts either, just turn the key, let the pump run for a little bit, one pump of the gas pedal and she fires right up!

[RWebb]

Originally Posted by esotoracing

EFI (other than originality or cuz you already have them, why even consider carbs or cis)

b/c carbs are cheaper & can be fixed in lonely places

a top quality EFI system is a wonderful thing but also very spendy