project Weber Carbuerators Into 1973.5 CIS Motor
 

I am going to put Weber Carbs on my 2.4 CIS motor... (please do not try to tell me how great CIS is ... (it is out) Except the ALUMINUM COLLARS that the injectors and rubber Was in.... There in is the problem!! Can anybody tell me how they removed the ALUMINUM COLLARS and how You PLUGGED the hole ?????? At this point I have not taken the engine from the car, nor have I removed the heads off of the engine...(which I am sure will bring disparaging remarks) Help from someone WHO HAS DONE this will be truly appreciated... Thank You in advance !!!!!!

drop the motor; remove pistons & cams and replace with ones for carbs

Usually an allen cap screw is threaded into the rubber injector holder. PN 911.110.922.00

Other options include:

- custom brass or aluminum plugs that press into the top of the injector holder tube.
- remove steel injector insert and then plug using these method.

You have been looking at this conversion since 2011. Why the extended delay?

must be from old gas

Sometimes these things require deliberation. I’ve been thinking about EFI on my 73 for about as long! ☺️

By the way, my 73 was converted from MFI to Webers and the injector openings were closed with threaded plugs. When I dream about EFI, I think about re-using those for the EFI injectors.

I can help with that. :)



http://forums.pelicanparts.com/porsche-911-technical-forum/809214-mfi-efi.html

BTW, the 73.5 CIS heads will also accept EFI injectors. Works the same as my adapters but without the adapters since the factory already installed them.

One of my barriers is that although I still have my original throttle bodies, they are shot. So, in addition to an ECU and all the other stuff, I'd need to get throttle bodies.

That just sparked a thought...

Could I keep my Webers as just throttle bodies (after blocking all the fuel inputs) and use the injection ports in the heads ?

EFI requires a way to sense the air flow. Individual throttle bodies do not accomplish this.

Not True. But ITBs do require a port added to detect vacuum. Works just fine without TPS. You just have to know how to tune around the "wall"

im not following??? if the 73.5 CIS mirrors the later versions aren't the injectors seated in the intake runners that would be removed for carb based manifolds? or could you be referring to the plugs required in the heads like the 74-79 air pump equipped cars after you remove the spider manifold ?

sorry if im way off base not being familiar with the earliest CIS systems. ive removed CIS for carbs on two early, large post 3.0L motors over the years so those are more in my wheel house.

I think the best thing to do for the OP would be to buy a 3.2L and either swap it in as is, or hotrod it while driving with the 2.7 CIS then swap. Sell the CIS motor later.

OK, did a bit of research and found this EFI conversion thread. http://forums.pelicanparts.com/porsche-911-technical-forum/1018391-2-4l-mounting-cis-intake-efi-conversion.html

I have a better understanding now, so my suggestion is place a WTB add in the classifieds and get a proper carb manifold. you can get the isolation spacers that block off the groove in the head intake and insulate the carbs from both heat and vibration from the motor.

If this is the case, then I have been schooled. Thanks!

The 1973.5 CIS motor is unique in many ways. One of them is that the injectors are in the heads not the intake runners which started in 1974.

1973.5 induction (note the injector ports in the head):

http://forums.pelicanparts.com/uploa...1577054468.jpg

1974 induction (note injector ports in the runners):
http://forums.pelicanparts.com/uploa...1553035313.jpg

Excellent visual reference Harry.

Sorry for the novice question, but am I correct to assume that the need to detect vacuum makes it a non-starter to use Webers as ITBs?

Novice question #2 - could ports be added?

Harry is quite right. The 73.5 was a special beast with heads more similar to the MFI cars, few of which came to the US. I haven’t studied that era in depth (mine is. ‘74) but I’m guessing that just like the rest of the CIS cars you’ll need to change pistons and cams to see any real improvement in performance. The CIS system needs a specific cam profile that does not work well with other induction systems.

I have a nice pair of 964 Camshafts with only 150 miles on them. These would work well with you motor with carburetors.