snakepitt1

I have a 1973 911T Targa, 2.4L MFI. I have been thinking about swapping the MFI set up for Webbers. The MFI system is starting to run lean again. It was adjusted and tuned by Pat Williams German Auto in Memphis about 500 miles ago and has started going lean again. I realize that techs who know MFI are literally dieing off, and there are very few souls left who have the experience to keep one of these systems properly tuned. So, to that end, I am thinking seriously about replacing the MFI with a set of Webber carbs.
Question: How difficult?
Question: How much am I looking at financially? (I would retain the MFI should I sell the car)
Question: What kind of performance feel would I or should I notice? If any

Thanks,
Scott Harris
1973 911T Targa 2.4L MFI

Steve Weiner-Rennsport Systems

Hi Scott:

Well sir, I do understand your dilemma. Its quite true that the core of experience with these MFI systems is quite small now, and many enthusiasts have as much (or more) experience than most Porsche technicians anymore.

There is no question that a good carb setup is easier to maintain, IF,........IF its installed and setup correctly; they do run very strongly.

That said, IMHO it will be cheaper to rebuild your throttle bodies and pump, than it will be to buy the $ 3000 PMO kit and you should consider both sides here. I would not sell or dispose of the MFI setup on the car, regardless.

Your decision will be based on economics and how mechanical you are.

BTW, I'd strongly suggest that you install the '73 spoiler/bumper to balance the tail you have. At speed, your car becomes a "motorboat",....

snakepitt1

Thanks for the honest response steve. I have a 911S front bumper going through the final stages of paint prep and paint before mounting. I'm doing the work myself, so it takes abit longer.
As far as the carb cost, Pat Williams in Memphis would be doing all work for this conversion and since he has worked miracles on my car in the past, one more minor one should be simple. Pat doubles as head mechanic on the white lightening AMLS Porsche team. Last time I sopke with him he was at Sears Point. He has the carbs in his shop and quoted the whole job at less than 3 grand. It's alot of money, but with the MFI running again way too lean, exhaust temps climbing to a point where the muffler was able to melt thermoplastic from 4" away and oil temps are basically uncontrollable, this swap will allow me to enjoy my car for long rides without fear of a fire or some other unforseen problem. For the record, I will retain the MFI system as long as I own the car.
Thanks

snakepitt1

bump

pwd72s

All else equal, I'm thinking you will experience a slight power loss if you go to carbs, and you will notice slower throttle response. It would be wise to keep the MFI in either case.

art

If you are a bit more adventurous you could build an EFI system. You can get the throttle bodies from TWM, and a computer from Haltech, SDS and probably others. The T engine should run well with it and you will have ultimate driveability, emmisions and reliability. You will need patience to set it all up, though it is not as bad as the MFI fiddling and once you get it functioning the changes are mostly programming.

I have found a few sites talking about the MFI, and you could get the manuals that cover it and become an expert for yourself and others.

Whatver you do, make sure you take time to gain the knowledge so you are not relying on others.

Art

Art

Tom F

I had a '72 T that had both MFI and Webers (at different times!). The MFI was definitely more driveable, but I don't think that there was any performance gain compared with the Webers. I would go with MFI, but be prepared to spend a lot. The little details, like the toothed wheels for the cam and pump, were really expensive. Just as Steve Weiner says, the cost to restore you MFI will likely be less than, or at worst the same as, the cost of the carb conversion, but it will probably be better to restore the MFI. You might want to find a Mercedes Benz old timer to work on the car. MB used a similar Bosch MFI system (actually a much better installation) from the 50s to the 70s, and it appeared on many more cars, so you might find a great availability of experienced people. Good luck with your project.

Steve Weiner-Rennsport Systems

Hi Paul:

Just a quick note on this subject,......

All things being equal, MFI & carbs make about the same power if the venturi's are the same size. Carbs make a bit more low & mid-range torque and MFI is a bit better on the top.

Carbs definitely have crisper throttle response as long as they are configured and setup properly. MFI has a bit of lag to it by comparison and especially when everything gets a little wear in it.

lateapex911

I'm leaning to the retain the MFI side of the fence in your case. Last I checked the guy in Redwood City CA ...Gus???....was still doing them.

If they are done right, with good parts in spec, they say they run great and last awhile.

Maybe this is a good time to do the MFI (with a good guy with the right flowbench, changing out the space cam, etc), and redo some items on the engine to bring it up to E specs for the rest of the 3K?

Just a thought... might get more bang for your buck.