throttle linkage slack problems

[Nick912]

Hey All,

I am rapidly nearing the end of my '67 restoration, and I realized today that with the accelerator matted my throttle was only opening a small amount.

Got underneath the car and found that the "slack" is in the coathanger-like fitting on the end of the linkage piece that attaches to the button fitting on the tranny bell crank and runs up through the engine sheet metal to a ball and cup fitting on the forward side of the fan shroud on the engine.

The button pops into the loop of wire at the rear end and then slides forward, but it only slides about halfway in that loop, so when I hit the gas pedal all of its travel goes towards sliding that button down the rest of the way on the wire loop, only at the end pulling it forward at all to open the throttle a little bit.

Apologies for the involved description, but I have tried to take up "slack" by screwing down the ball fittings in various places but it's not enough. Should I just twist the end of the coathanger-type fitting to shorten it up? ALL suggestions welcome!

Thanks!


Nick

[WFBowen]

Nick:
(re: illustration below)
Make sure that the long rod from the front bellcrank (at the pedal assembly) is shortened up and that the rods go all the way into 32 & be certain that there's no slack in that coupler. The bellcrank and rod mounted on the rear of the fan housing are often overlooked. The proper angles of all of the bellcranks are important not only in getting full throttle, but the rate at which the throttles open, so it's worth some frustration in getting everything right. My current 912 works fine with the angle of part 35 rotated just slightly clockwise from the position illustrated.

That said, in the 70's I had an early 912 with the same situation. After hours of messing with it, I ran it up to Glendale (Ca) to these factory trained German Porsche mechanics (they raced a 904 and worked on the best of the 911's.) I didn't even have to finish my description of the problem when one of them just got in, ran it on a lift and cut part #36 between the slot and the arc in it. He then took all slack out and held it in place with some tiny vicegrips. Then he checked for full throttle and brazed it together in its new position. Problem solved, but it wouldn't impress a concourse judge crawling under there.
Hope this helps,
Bill.

[Nick912]

Bill,

thanks for the info and the diagram, I think I'll most likely go with a variant of your option B because if i rotate part 35 enough to take up the slack the arm will be near 6oclock and further rotation would interfere with part 36 (they would just jam against eachother having run out of lateral motion).

Thinking i might be able to separate the coathanger part of part 36 from the arc part as it looks like they're pressed together. Just shorten it an inch and half and then repress them and tack 'em together.

Cheers,


Nick

[djdsc]

The most often over looked adjustment is the link that connects #35 up to the cross bar mounted on the front of the fan housing. The vertical link behind (in front of) the fan shroud should be almost as long as you can make it, so that the bellcrank #35 on the fan shroud has the proper range of travel. Changing that will affect all of your geometry in relation to #35. There are at least 5 points of adjustment just from #s 24, 25, 26 to #35.

[w6zo]

Let's think about this - it must have worked right at some point. Why would you need to radically change things to make it work right again? Go through it from front to back. Most often the bushings in the pedal cluster are non-existant. Probably the most common problem. Replace #32 with the modern replacement part - the most common point of failure after the bushings. It just doesn't make sense that you would have to bend up the "coat-hanger" unless it was to compensate for another problem somewhere else, does it???

[Nick912]

Ended up only needing about 3/8ths of slack taken out, so I unscrewed the ball cup at the end, nipped about 3/8ths off, threaded about another 1/4inch of the rod, and replaced the ball cup. So far so good.

Thanks for all the input!


Nick