Advice on 911E Engine Rebuild with Carburetors

[chris belyea]

I recently purchased a 1970 911E outfitted with Webers rather than the MFI. The engine has about 140,000 miles on it and there is oil on the 3 of plugs so I know the valve guides are going or gone. The engine does backfire and pop quite a bit so I don’t know if it’s carburetion, fowled plugs or both. I am considering a rebuild. Can anyone tell me what the pros and cons of sticking with carburetors vs. MFI and what modifications/setup I should do during the rebuilt to accommodate carburetors?

Thank Chris

[Schwarzeritter]

It really depends on what type of driving you are going to be doing, furthermore what your expectations in terms of performance are going to be. Could you elaborate a little more on what it is you are trying to overall acomplish?

[chris belyea]

My driving is mainly around town. I'm not looking at racing. I think at a minimum, I'd like the engine to be setup to drive and have fun. I'd rather not have to tweek the engine every few weeks because it's a super high performing engine but at the same time, I'd like to keep performance as close to what it was originally. If I can get a little more power out of it without having to spend every weekend in the garage making adjustments, great.

Does that help?

[Henry Schmidt]

The pro and cons are fairly simple.
The MFI system offer better throttle response and more consistent tuning.
It also offer originality and for some Porsche owners that is paramount.
The cons are expensive to acquire a complete, functioning system, difficult to tune properly and horrible fuel mileage (in some cases fuel yardage )

With the carbs you get easier tuning and they're cheap because you own them.
The down side of carbs is they tend to stumble under aggressive cornering, they have no provisions for cold start, they need constant tuning and they always smell like gas.

The second part of your question is also fairly simple. 911Es are very well suited to carbs. I would think about upgrading the cams to Solex or Mod Solex because they seem to be the best compromise for carbureted engines.

[larrym]

you should read this - http://rennsportsystems.com/letstalk-2/5-how-to-make-your-porsche-faster-na-engines-1/

you will also find some parallel discussion of potential interest on this thread

Is installing a 70.4mm crankshaft into a 1969 crankcase just plug n play?

as an old-timer I like webers cuz i can fix & tune them - i don't have the special tools & testers to work on injection

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