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Thread: 1973.5 cis injection replacement

  1. #1
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    Aug 2013
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    1973.5 cis injection replacement

    cis injection on a 2.4, Wanting to replace with weber carbs.
    Ive got the carbs, Manifolds and linkage.
    Not sure about the fuel pump, Fuel Regulator, Ect.
    Do I need to change the injection fuel pump or can I
    buy the PMO fuel regulator from pelican and have it
    tone down the P.S.I from my current fuel pump?
    Any Advice, Suggestions, Experience Greatly Appreciated!
    Car is a 1973.5 911T 2.4 with cis injection.

  2. #2
    Banned
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    Gotta ask why you would do this?

    Piston dome shape and cam profile does not lend itself well to carbs.

  3. #3
    Quote Originally Posted by Frank Beck View Post
    Gotta ask why you would do this?

    Piston dome shape and cam profile does not lend itself well to carbs.
    Car was parked for twenty five years, Got
    The engine to fire up and run by pouring small
    Amounts of gas down pop off valve.
    Injection is Brittle, Frozen and in need of
    Expensive replacement NLA parts.
    Just want to get engine running and
    911 drive able.

  4. #4
    Senior Member
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    New York
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    This came up on Pelican, and I was told the CIS cams work well with Webers.
    I got rid of the Webers on mine and went back to CIS. Much better for every day driving. I've seen quite a few 73 cis systems come up over the years. I currently have 2 setups, the second one cost about $200. It was dirty and needed a lot of clean up. but the components were all good. Many parts for the '74 are interchangeable, aside from the intake runners and injectors. I was able to get the piston rings from PartsKlassik. NLA everywhere else. They told me they had Goetze do a run just for them.
    Pelican classifieds seem better the parts, not many cis on this forum.
    E Sully
    1973.5 911T

  5. #5
    Junior Member
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    Aug 2013
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    Thank you E Sully for your input, I'm going
    To attempt to buy the CIS parts that I need
    And keep it original. Obviously I'm a complete
    Noob!

  6. #6
    Senior Member
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    Aug 2011
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    New York
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    Princess,
    You're this far along, try the carbs. You may like them. There is nothing really wrong with the Webers. Webers are fun and it adds a more sporty sound to the car. Minor drawbacks, cold starts are a little difficult without a choke, gas mileage will be lower, it will take a bit to get the jetting right.
    I don't know if you are doing the work yourself, or paying a mechanic. I do 90% myself with helpful hints I pick up searching the forums, and talking to the guys at the local Porsche shops. I found the cost of Webers to be more than fixing the CIS. Most have been used quite a bit, and having them rebuilt by the qualified shops can cost quite a bit if shafts are worn, passages and jets are clogged, etc.
    Scan the Classifieds for deals and pick up the bits and pieces for the CIS when you find good deals. Like anything else, diffferent people sell at different prices. Like I said earlier, every once in awhile I find parts from people like you that switched to carbs, or swapped out to a 3.0 or 3.2 and sell the CIS or complete engine cheap. Others want big dollars since it is a unique 6 month only setup. If your engine is original to the car, saving it will keep it's value higher down the road. Like I said, I ran Webers, I also rebuilt and ran a 1986 3.2 in the car for a few years. The thing I like to do is save all the original parts, and any modifications must be easily reversible. I'm older now, and while it was fun modifying things in the past, right now I'm restoring it all back to original.
    http://www.ebay.com/itm/Porsche-911-...8385c9&vxp=mtr
    http://www.ebay.com/itm/Porsche-911-...72810d&vxp=mtr
    Last edited by ESully; 08-24-2013 at 08:59 AM.
    E Sully
    1973.5 911T

  7. #7
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    Aug 2013
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    Great Advice E Sully, And Greatly Appreciated!
    My Jetronic is complete but all of my lower pressure(Soft)
    Fuel lines are Brittle and need replacement.
    Researched the system and really like it.
    Replaced my Fuel pump and got my engine to
    Run but the amount of fuel leaks I found was enough
    To shut down progress until I replace them.

  8. #8
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    Aug 2013
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    Dealing with injection ports in Heads

    So I started to take off my injection so that I can try and Diagnosis what is needed and thought id mount my carbs to see if I could
    get the 2.4 to run and drive.
    My question is what do you do about the injectors? I know I can pop them out but how do you Plug the holes to run carbs?

  9. #9
    Senior Member
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    New York
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    I took one of the injectors to a shop by me and had him machine plugs out of aluminum using it's dimensions. He charged me about $75.
    Name:  CIS0031272982651.jpg
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    E Sully
    1973.5 911T

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