Wacky MFI questions... again

[tadd]

Ok, threes a charm!

So I took the jump and purchased a 70/71 'S' MFI pump from evilbay last night and am planning for the next few steps...

BTW this will eventually go on a 69T to be upgraded to S specs (cam & pistons).

Q1: Has anyone done a rebuild themselves? I have done two diesel injectors on the kitchen counter (much to the chagrin of the misses ). I realize the gasoline pumps are more complex, but after having waded thru the manual it does not seem to bad if you know how to use a dial gauge and a digital caliper. It wouldn't be too bad to build a small test stand to spin the pump with an electric motor to dynamicly set the pump output although I don't know what to use instead of gasoline (right scary that would be), kero maybe?

Q2: Did anyone mount the pump in another spot than off the cam? Reading posts about the 'devil bolt' are not encouraging, so why not hang it off the nose of the crank as another accessory (after changing the pully ratio of course) so you can get to the darn thing.

Q3: Why is the TB linkage so damn complicated? Even porsche on the 73-74 RSRs ran the butterfly shaft 'long axis' and then used a bell crank to rotate the motion 90* to interact with the pump. With all the flies on one shaft the entire bank is naturally 'in-sync' and balance between the banks would be a single tierod adjustment. I guess my thinking is that it wouldn't be too hard to make my own TBs and then top them off with some V stacks. I have seen complete MFI systems for sale, but I haven't come across any TBs since they seem to crack.

Thoughts?

tadd

[kenikh]

Originally posted by tadd
Ok, threes a charm!

Q2: Did anyone mount the pump in another spot than off the cam? Reading posts about the 'devil bolt' are not encouraging, so why not hang it off the nose of the crank as another accessory (after changing the pully ratio of course) so you can get to the darn thing.

tadd

Since the cam rotates much more slowly than the crank, I don't think you'd have a great deal of luck driving the pump off of the crank, even if you did change the wheel sizes. I'd bet it would be a ***** to time and tune if you weren't able to time it off of the cam.

[davidppp]

Hello there.

I never heard of it..and the weight further back in the car is not ideal..but it will work IMHO.

Obviously you need a 2:1 reduction.but apart from that.no problem..

Kind regards
David

[tadd]

Oh, come now... I just finished a thread about people wanting to make copies of the protractors for tuning MFIs at a reasonble cost. This board has some amazing DIY work. The thread on machining your own twin plug heads was great, and I can't wait to try it... Heck, folks are going on about casting their own cases and doing the finish machining which on a casting is darn tricky!

But you can't tell me that NO ONE hasn't rebuilt their MFI pump that does not get paid to do it.

I would never consider asking a pro who makes his living doing such things, to answer, but someone in this vast porsche world must have done this once or twice and be willing to share their experiences.

I am going to jump into the great abyss regardless when my pump comes, but it would be nice to know what to watch for.

Cheers,
tadd