73 MFI to CIS when did it change

[dmcummins]

Im just curious as to when they made the change from MFI to CIS. I have a 73, but not the original engine. I assume it originally had CIS as thats whats in it now.

My serial # is 9113102450

The engine that is currently in the car is from a 72 #6122522. Im having cold start problems and I'm waiting on a few parts from pelican to hopefully sort this out. I'm also going to do a leakdown ect to see where I'm at.

Anyway, I'm planning on at least buying a correct year longblock or case at some point and want to make sure I pick up the correct type.

[kilodawg]

I don't have your answer but my '72T has MFI and the build month was 11/72

[HarryD]

Porsche started using CIS for the 911T in the middle of the 1973 model year. In 1974 both the 911 and 911S had CIS and the 1974 RS Carrerra had MFI. All '72s had MFI.

If you have a '72 then you should have a MFI Car unless your engine was replaced. Besides the serial number on the engine nearby is a code that reads something like 911/xx. That will be the code for your engine type.

This site can help you decode the whole mess: http://www.elferhelfer.com/fzident/fzident72-73.htm

From this site, it shows you have a 1973 911T Coupe Body and a 1972 911T engine but since CIS did not come to Porsches until mid 1973, that was done after it left the factory.

Also, FWIW, your car came with Factory Air but where are the compressors, condensers etc?

Another bit of help:

Originally Posted by ossiblue

My understanding of the general rule is this, using the 1973 911S in your screen name as an example:

Your VIN would be 91133XXXX, with the fourth digit (3) indicating the year and the fifth digit (3) indicating the car is an S model.

Your engine number should be 633XXXX, with the second digit (3) indicating an S motor and the third digit (3) indicating the model year of car it goes in. In short, the fourth digit of the VIN should match the third digit of the engine # and the fifth digit of the VIN should match the second number of the engine #.

If you want to know if the motor in your car is the one that was installed in the factory, I believe that can only be determined by a COA. Having matching numbers, as indicated, shows the proper engine for the proper year and model of car, not necessarily the exact engine that came with the car.

You can follow the general rule, above, and substitute different model years for the fourth digit--0 for 1970, 1 for 71, etc., and the model type (fifth digit) will be a 1 for a "T", 2 for an "E, although I have seen a 5 in this location which was for a ROW "T". In the engine #, not only will the third digit (year) change, but the second digit may also--1 being a "T", 2 an "E.

Hope this helps. Others who are more expert will add refinements

[TVRLOTUSTR3]

I don't think your car is a 72. You don't have the oil door on the right rear fender.

[dmcummins]

Originally Posted by HarryD

Porsche started using CIS for the 911T in the middle of the 1973 model year. In 1974 both the 911 and 911S had CIS and the 1974 RS Carrerra had MFI. All '72s had MFI.

If you have a '72 then you should have a MFI Car unless your engine was replaced. Besides the serial number on the engine nearby is a code that reads something like 911/xx. That will be the code for your engine type.

This site can help you decode the whole mess: http://www.elferhelfer.com/fzident/fzident72-73.htm

From this site, it shows you have a 1973 911T Coupe Body and a 1972 911T engine but since CIS did not come to Porsches until mid 1973, that was done after it left the factory.

Also, FWIW, your car came with Factory Air but where are the compressors, condensers etc?

Another bit of help:

Thanks, It looks like my car originally would have been a cis car which makes sense. I assume the original longblock was trashed and someone swapped the 72 motor in its place. Looks like I need a engine # between 6133001 and 6136092.

I pulled the AC parts off as the hose's were rotten and nothing worked. How could you tell it was origninally a AC car?

[HarryD]

Originally Posted by dmcummins

Thanks, It looks like my car originally would have been a cis car which makes sense. I assume the original longblock was trashed and someone swapped the 72 motor in its place. Looks like I need a engine # between 6133001 and 6136092.

I pulled the AC parts off as the hose's were rotten and nothing worked. How could you tell it was origninally a AC car?

Glad to help.

How did I know you had AC?

Easy. If you look at your coil, there is a mounting plate that moves the coil closer to the engine. Porsche did that to avoid the coil hitting the Engine Lid condenser.

If you really want to get into the tiny details, visit the folks at the Early 911S Registry BBS (http://www.early911sregistry.org/forum/index.php)

[Bobboloo]

You can also see part of the bracket for holding the compressor next to the oil pressure sender.

The CIS system you have is definitely from 73.5'. That's the only year that the intake runners were made from steel. Starting in 74' they were all made from cast aluminum.

[jwerion]

I think what you are looking for is 2.4 liter 7R case as these where the ones used on the 73.5 CIS motors. All the later 7R cases will be a larger bore for the 2.7 liter motor. I have one of these cases listed on e-bay but I don't know the case number at the moment. If you are interested I can check the case on Sunday.