2.7L CIS to MFI conversion
 

I have a 1974 911 with a very tired stock 2.7L CIS motor with 110,000 miles on it. It's never been rebuilt, and as you might imagine I need to carry oil around with me and dump some in every time I get gas, which is often because it gets terrible mileage.

I've been considering options for rebuild:

1) The logical, cheaper choice: Wayne's book suggests 90mm JE pistons (CR 9.8:1) and 964 cams.

2) Converting the car to the 1974 Carrera 2.7L w/ MFI, and changing the wheels and flares and adding a duck tail. I like the look of the 74 Carrera.

3) Converting the car to the 1974 Carrera RSR w/ 3.0 L MFI, and changing the wheels and flares and adding the rear wing.

I'm having trouble finding decent info on converting an engine like mine to either the 2.7L Carrera MFI engine, or to the 3.0 L Carrera RSR MFI engine (I realize the RSR is probably a pipe dream since very few were made). But either way, does anyone have any info on how difficult and more expensive options #2 and #3 would be than just sticking with the CIS motor w/ new pistons and cams? This car is primarily for street use w/ occasional track use.

Thanks in advance for your help. These forums are very educational.

I can tell you from experience that it is expensive to run MFI and takes a lot of time chasing down parts. For performance it is easier to look at PMO carbs and probably less complicated. You need to decide what you are going to use the car for before you start making big changes. DIY rebuild for 2.7 is probably 10K to do it correctly with proper machining and parts. Might want to contact Henry for estimates and modifications but I think you will be surprised at how fast the dollars add up.

Street use = keep it mild. A 3.0 RSR with MFI setup to period specs would be horrible around town, use race gas and be way overkill.

For a street car, I would stick with the CIS cams and pistons and convert to Megasquirt.

If you think you get poor fuel mileage with CIS, MFI will cut that in half......I agree with John - Megasquirt...

You will need;

1. Pistons appropriate for the S cams

2. The S cams (with mfi end)

3. 2.4 S throttle bodies,stacks adn all necessary linkages (can be any plastic stacks/throttle bodies bored appropriately) Truthfully I would go a bit bigger than the RS spec.

4. any year injection pump recalibrated with the rs space cam

5. heads modified for injectors,not sure about valve size but will need port work also.

6. injectors

7. recurved dizzy


If I have missed something please add.

The MFI'd engines need special attention from time to time but are very rewarding when driven hard.

Where do you find info on the MEGASQUIRT system?