1973 1/2 cis

plumber · 06-09-2010, 07:18 AM

What are the disadvantages to this motor & injection system for this year?
The cis was changed in 1974 for the 2.7ltr.
I hear the parts are hard to come by & this motor should be avoided, what's the consensus?
I think the cams were changes for the T motor with cis in 1973 is this a problem?

mikeferg75 · mikeferg75's Garage

I love the motor (when it's working properly) I have owned 3 73.5 T's and they make wonderful drivers.

But you are correct, they have many half year only parts and can be hard to put right, if the car is a project. The entire CIS is unique to that half year, so is the gas tank ect. Some retrofitting can be done, but not much.

plumber · 06-09-2010, 10:04 AM

So if the car is complete & not a project it's a good car untill something associated with the engine &/or CIS has a problem.

mikeferg75 · mikeferg75's Garage

Yes, but a PPI by someone who knows early cars is still a must. You can adapt things to make the cis "work" but it's not always optimal.

sithot · 06-09-2010, 04:44 PM

The CIS T is a no brainer, imho. No injection pump to deal with. No throttle bodies to be rebuilt. No PITA tuning procedures. Tuning it is a one screw affair. Don't worry about the "fuel distributor". They rarely go bad and if they fail its due to a lack of care and the most likely culprit will be water (or really bad gas!). The CIS cars don't like water AT ALL. If it's been poorly cared for the metering plate will get pin-holes in it and you'll know it because it will smoke like a mosquito fogger.
You cannot radically hot-rod them because the CIS doesn't react well to hot cams due to the pressure waves created in the airbox.
It's a bullet proof system for the most part with nothing more than one moving part. Were it not for stricter emission regulations it may have gone for a few more years. It WAS used by the Turbo cars all the way until 1994. Enough said.

Good luck.

Tom

plumber · 06-10-2010, 03:25 AM

Thanks for the info.

Fidalgo911S · 06-10-2010, 07:35 AM

Fuel filters are hard to come by as well.

sithot · 06-10-2010, 08:07 AM

Pelican shows them: Porsche 911 CIS Fuel Injection - Page 1
(updated fuel filter setup)

If you cannot get it here A U T O H A U S AZ has the same thing. (0450 905 016*) or one without fittings (021 suffix) This depends entirely on whether you have the updated fittings or not. Restrictions kept me from leaving a link but you can figure it out.

SSF and PCNA are generally your sources for all of this stuff if you ARE a Porsche parts wholesaler.

Tom

Fidalgo911S · 06-10-2010, 08:34 AM

Good info. I have the old filters on my '74 but have yet to persue the options yet. I still have a small stash of the old kind. Thanks,

Nate

Sunroof · 06-15-2010, 04:48 AM

Plumber,
I have had my 1973.5T/CIS for over 10-years now and pretty much replaced several of the systems. The CIS despite the number of components is well matched with the 2.4. Parts are easy to find for these cars and better yet several companies offer rebuild parts like the CDI unit, fuel distributor, and warm-up regulator for starters. The real unique part of the 73.5T model is the fuel injectors which go directly into sleeves on the cylinders unlike being inserted into the intake runners on the 1974 and up models. No big deal here!

The warm up regulator can be updated to the newer versions with a retrofit (fitting kit). The fuel filter can be updated to the new filter thats easy to install and is not that expensive. I highly recommend the fuel filter update.

Indeed, the 1973.5T has very unique features only unto itself (gas tank, no thermotime switch, hand throttle, first fuel distributor, rear mounted fuel pump, etc), but take it from a 1973.5T owner, I have yet to be challenged to replace any parts thus far and believe me just about everything has been replaced or restored on my car. The only complaint I have with this model is the "hot start" issues. The fuel pump is mounted to the rear in the left wheel well. So you have a good stretch to pull the fuel back. The OEM pumps came with an internal check valve, which helped a bit, but not enough. So you have to add an external check valve on the replacement units and on hot days as the fuel volatilizes, getting those cylinders to come alive takes a bit of time to recharge the injectors. In 1974 and forward the pumps were mounted forward just above the rack.

The 1973.5T is a very unique car in that its the last of the "longhoods". Its 2.4 block has never been known for overheating issues, it's a strong runner and with the 915 transmission is an absolute kick to drive. Okay its does not have the speed of the "S" nor the "E" but in city traffic and mountain roads its a blast to drive and will holds its own. I think the 1973.5T is a great car and will continue to be a popular model to own and enjoy.

With Pelican support and a good list of parts vendors, manuals (Waynes 101 Projects for example), etc, in my 40+ years of Porsche ownership, owning and maintaining a Porsche has never been better!

Good luck
Bob

blau911 · 06-15-2010, 05:27 AM

Bob, after that informative and lengthy post, I believe a pic or two of your car is appropriate.

Quote:

Originally Posted by Sunroof

Plumber,
I have had my 1973.5T/CIS for over 10-years now and pretty much replaced several of the systems. The CIS despite the number of components is well matched with the 2.4. Parts are easy to find for these cars and better yet several companies offer rebuild parts like the CDI unit, fuel distributor, and warm-up regulator for starters. The real unique part of the 73.5T model is the fuel injectors which go directly into sleeves on the cylinders unlike being inserted into the intake runners on the 1974 and up models. No big deal here!

The warm up regulator can be updated to the newer versions with a retrofit (fitting kit). The fuel filter can be updated to the new filter thats easy to install and is not that expensive. I highly recommend the fuel filter update.

Indeed, the 1973.5T has very unique features only unto itself (gas tank, no thermotime switch, hand throttle, first fuel distributor, rear mounted fuel pump, etc), but take it from a 1973.5T owner, I have yet to be challenged to replace any parts thus far and believe me just about everything has been replaced or restored on my car. The only complaint I have with this model is the "hot start" issues. The fuel pump is mounted to the rear in the left wheel well. So you have a good stretch to pull the fuel back. The OEM pumps came with an internal check valve, which helped a bit, but not enough. So you have to add an external check valve on the replacement units and on hot days as the fuel volatilizes, getting those cylinders to come alive takes a bit of time to recharge the injectors. In 1974 and forward the pumps were mounted forward just above the rack.

The 1973.5T is a very unique car in that its the last of the "longhoods". Its 2.4 block has never been known for overheating issues, it's a strong runner and with the 915 transmission is an absolute kick to drive. Okay its does not have the speed of the "S" nor the "E" but in city traffic and mountain roads its a blast to drive and will holds its own. I think the 1973.5T is a great car and will continue to be a popular model to own and enjoy.

With Pelican support and a good list of parts vendors, manuals (Waynes 101 Projects for example), etc, in my 40+ years of Porsche ownership, owning and maintaining a Porsche has never been better!

Good luck
Bob

Sunroof · 06-15-2010, 07:26 AM

blau,
You not the first one to request this! I have yet to take any digital photos to download, but I can tell you that the previous owner did a bare metal restoration and repaint and kept it in original Sepia Brown. It has the "S" trim package complete with the chrome wheel well trim pieces. I added the gold 911T and P.O.R.S.C.H.E script on the engine lid that really enhances the appearance with the Sepia Brown. In my early days of Porsche ownership, getting those hand painted center caps for the polished fuchs was the thing to go after! Luckily for me, it came with those too. Add like new amber fogs, chrome light trim rings, and an original rust free body and you have gorgeous example of the mark.

I will try and get something posted soon.

Bob

techweenie · techweenie's Garage

CIS is a good system when it works. So many things you can do to diagnose it yourself, and there's basically just one adjustment. As for the WUR, it's a simple unit that can be rebuilt. God forbid you flood the engine. Just plan on pulling all the plugs.

I've had over 30 911s -- including several 73-1/2s -- and the CIS cars are economical at the sacrifice of 'crispness.' But the torque is good. Keep in mind that 140 HP in a 2272 lb. car will quickly teach you not to do any stoplight racing with current econoboxes.

zioo · zioo's Garage

Tom--thanks for that information which indirectly provided me material for my 1984 911 restoration project-zioo, Ca