CIS on a modified 2.4
 

Hi,
My father in law has a 1972 911T Targa that he wants me to do an engine for. I am planning a mildy reworked 2.4 with 2.2 E spec cylinders and pistons. The car currently has Webers and an MSD ignition on it and they are in good working order. Unfortunately my father in law and his son are having quite a lot of difficulty with starting the engine in it's current form as the driving season in northern Michigan extends from freezing to freezing. I am well familiar with CIS injection and would prefer to just fit the CIS from a later engine on it and see if that clears up the problem for them. However most of what my father in law has read has been critical of the CIS system.

Here are my questions:
Can I fit CIS engine a still make a mildly entertaining engine for him? I am not out to create a rocket ship but don't want to kill the performance totally either. If I can do this which cam grind would you recommend?

CIS is a good system provided everything is right:

1) Control and System pressures from cold to hot.

2) NO vacuum leaks.

3) Injectors have the correct spray pattern.

4) Thermotime switch (in early versions) is working properly.

Max cam grind in any CIS engine would be the 964 one.

The only issue with CIS is the lack of new parts. Bosch & Porsche discontinued all support a few years ago and we are all on borrowed time with these fuel systems until there are no more good used ones to recycle.

Now,..............Webers run VERY well when properly setup & adjusted, however they lack a choke or cold-start system and rely completely on the accelerator pumps for starting enrichment. Further, it takes some instruction for someone to learn how start them from cold and without guidance, will be very frustrating.

LOL,...Your F-I-L may be my age and I'd be happy to explain to him how to start them from cold (and hot).

I can start it but they just lack the feel for it. I used to teach for BMW but I don't think I can teach that. But, the plan is to do the rebuild in the winter next year so any tips would be appreciated. Maybe if they can get reliable with the Webers we can keep them.

I totally understand what you are saying, however that simply means some additional education is needed for "enlightenment". I do this all the time with my clients since many of them lack the same experiences that I have (I'm an old guy and have been doing this since 1961).

All this means is that you or someone needs to invest the time to teach some fundamentals so they understand what a carburetor does and in basic terms, how it works. I've always had success doing this in terms that people can understand so I know its possible. It just requires patience and explaining things in non-technical terms.

Remember now, you aren't teaching them how to adjust or fix things, you are simply giving them the theory of operation and what happens when they press the pedal. :) :)

good and bad?
 

The carbs will use more fuel but work well enough( if in good condition) and provide a nice power curve,IMHO cis is fine when its working,I also think used systems can be a bit of a risk unless removed recently from a good running car,stuff goes bad lying around after all.
Just need to ask are you running stock air cleaner ?

Steve,
I would like to hear your starting procedures. I am pretty well versed on what it takes to rebuild what I need to on the CIS so that end of it does not scare me too much. I grew up working in a foreign shop where we routinely rebuilt the parts we needed.

Forgot to reply to Porschetub: Yes, stock air cleaner.

I would think that a 2.7 cis would be needed if you went that route. The 1973 2.4 cis used injector ports in the heads, but the 2.7 had the ports in the intake runners. The cis is sensitive to cam choice and from what I've read the 2.7 S cams are the only upgrade that would work over the stock 2.4 cis cams. Fuel pump would need to be obtained also. Does the fuel tank have a return line? Would you need to install a later cis fuel tank for the swirl pot and return line? I am interested to see what others think about swapping to cis, and wether or not it would work with the E spec pistons and cylinders.

72t
 

If the 2.4 is a USA 1972 they came with MFI. That would provide good cold start and bring the motor back to stock.