CIS Throttle Body Re-bush

[porschedude996]

I’ve been looking for information and parts to re-bush the throttle shaft on my 1983 911SC. I can’t seem to find anyone that has done it. I have about .010” shaft play. I think it should be in in the .003” or .004” play/clearance. I think i’ll have to throw some brass in the lathe.

[PeteKz]

Paul Abbott does this for Weber carbs, so he should be able to do it for the throttle body. However, you are pretty good on making parts, so you should do it yourself. As you probably know, the hardest part will be getting the shaft centered in the worn bore, because the wear will be oval and off center.

Performance Oriented

[porschedude996]

Hi Pete, thanks for the lead. Since my post I took the body apart and found it was easy to remove bronze bushings. A 3/8-16 tap fit perfectly and with my tapping block to keep things square, I only needed two threads to get them out. The first one spun out with just the friction of cutting the thread. Second one I went the same depth and it pulled out. No damage at all, not even a nick on the body. Things got easier than that. I was able to source Bronze Graphite 8mm x 11mm x 30mm. If the tolerances are what they say, all I need to do is chuck one up in my lathe and part two at 7mm lengths.

Originally Posted by PeteKz

Paul Abbott does this for Weber carbs, so he should be able to do it for the throttle body. However, you are pretty good on making parts, so you should do it yourself. As you probably know, the hardest part will be getting the shaft centered in the worn bore, because the wear will be oval and off center.

Performance Oriented

[PeteKz]

Excellent. Now you've got me thinking that I should go check my CIS throttle body...

[porschedude996]

If you look down the bore you may see some bright spots where the butterfly has touched the venturi. But of course the standard pushing the shaft back and forth.

Originally Posted by PeteKz

Excellent. Now you've got me thinking that I should go check my CIS throttle body...

[Jay Laifman]

I just did a smoke test on my 73.5 and found trace smoke coming out of the throttle shaft. I also sprayed some starter fluid on the throttle shaft while it was at idle. It caused the idle to drop.

So I'm looking at whether I should do this to mine. Anyone know if there are parts available? If I should instead try to find a replacement throttle? Mine has 180,000 miles on it.

[porschedude996]

Measure the OD of shaft, and the ID of the Casting bore. Mine was 8mm shaft diameter and the casting bore was 11mm. I was able to find standard stock material and machined to lenght.