914-6 creation with 69 911S motor, Carburetor or 69S MFI? Options

[ClayPerrine]

I had (and still have) a 2.4ST motor with MFI on it. I ran it my six conversion for years.

MFI runs great, and sounds tremendous. But unless you have someone to either teach you how to set it up and tune it, or you can pay someone to do it, then it is a bear to keep running correctly.

The thermostat on the MFI pump can be setup to work with heat exchangers. I was lucky, I got a set of 916 heat exchangers for mine. but it is simple enough to add the proper pipe to feed hot air to the pump. As for the engine tin, It is not hard to modify it to work with MFI. The only piece you have to modify is the right rear where the pump drive is located. I cut the tin and built a cover out of the 911 cover that worked great.

The cold start system is very primitive. It is nicknamed "the firestarter" for good reason. I never hooked it up. So starting the car on really cold mornings was a real process. I kept starting fluid in the car, and I had K&N watershield air cleaners. I would spray a shot of starting fluid under the air cleaners and try to start it. It would cough, sputter, spit and run on 4 cylinders, gradually adding cylinders as it warmed up. Oh.. and a hand throttle is an absolute must when running MFI. You have to use it to hold the throttle open while it warms up. About 10 minutes of letting it warm before trying to drive it.

But once it was up and running, it was a blast to drive. Phenomenal throttle response, and the sound would raise the hair on the back of your neck up. It sounds like the 917 in the movie Le Mans at full song.

I have a 69 911S MFI pump, and I considered putting MFI on the 4.0L motor. But I wanted a car that I could turn the key and drive, so EFI won out. I do miss the MFI sound and throttle response.


There is a video of my car with MFI out on Youtube if you want to hear it. It was wet that day, so I couldn't really open it up. Too much wheel spin.


https://www.youtube.com/watch?v=UHzPt2H5h0Q

[Cornerlot]

My previous 914-6 had a built 2.8L with RS spec MFI. Yes, it was difficult to cleanly start cold. It was fitted with a manual enrichment switch on the dash; "ignition on, hold cold start switch for a count of 8 with full throttle then engine crank to start". It was easy to flood and often idled badly or stalled when cold. The MFI pump is also a potential source of oil leaks.

Never ran the engine with carbs, so I can't say for sure about improved warm engine performance other than the throttle response was pretty sharp. Was it worth it, not really. Well set up Webers will do most cars quite well.

[Jett]

MFI all day. My '69 911S was one of my favorite rides, that motor was incredible

Beautiful car! I have onky watched a video of the motor rev’ing and was shocked at the acceleration.

[Jett]

I had (and still have) a 2.4ST motor with MFI on it. I ran it my six conversion for years.

MFI runs great, and sounds tremendous. But unless you have someone to either teach you how to set it up and tune it, or you can pay someone to do it, then it is a bear to keep running correctly.

The thermostat on the MFI pump can be setup to work with heat exchangers. I was lucky, I got a set of 916 heat exchangers for mine. but it is simple enough to add the proper pipe to feed hot air to the pump. As for the engine tin, It is not hard to modify it to work with MFI. The only piece you have to modify is the right rear where the pump drive is located. I cut the tin and built a cover out of the 911 cover that worked great.

The cold start system is very primitive. It is nicknamed "the firestarter" for good reason. I never hooked it up. So starting the car on really cold mornings was a real process. I kept starting fluid in the car, and I had K&N watershield air cleaners. I would spray a shot of starting fluid under the air cleaners and try to start it. It would cough, sputter, spit and run on 4 cylinders, gradually adding cylinders as it warmed up. Oh.. and a hand throttle is an absolute must when running MFI. You have to use it to hold the throttle open while it warms up. About 10 minutes of letting it warm before trying to drive it.

But once it was up and running, it was a blast to drive. Phenomenal throttle response, and the sound would raise the hair on the back of your neck up. It sounds like the 917 in the movie Le Mans at full song.

I have a 69 911S MFI pump, and I considered putting MFI on the 4.0L motor. But I wanted a car that I could turn the key and drive, so EFI won out. I do miss the MFI sound and throttle response.


There is a video of my car with MFI out on Youtube if you want to hear it. It was wet that day, so I couldn't really open it up. Too much wheel spin.


https://www.youtube.com/watch?v=UHzPt2H5h0Q

sounded great! Thanks for sharing!

My mechanic is a legend race motor builder and tuner, but he does talk of retirement.

[Jett]

My previous 914-6 had a built 2.8L with RS spec MFI. Yes, it was difficult to cleanly start cold. It was fitted with a manual enrichment switch on the dash; "ignition on, hold cold start switch for a count of 8 with full throttle then engine crank to start". It was easy to flood and often idled badly or stalled when cold. The MFI pump is also a potential source of oil leaks.

Never ran the engine with carbs, so I can't say for sure about improved warm engine performance other than the throttle response was pretty sharp. Was it worth it, not really. Well set up Webers will do most cars quite well.

Thanks. We have the carbs as backup (IMG:style_emoticons/default/smile.gif)