911 trannie clutch fork question

[speedo]

My racecar is a 71 and uses the 70-71 interim "pull" type trannie...meaning the clutch fork pulls the throwout bearing away from the pressure plate. This occurs as the shift cable pushes the bottom of the clutch fork towards the engine, while the top of the fork pulls the throwout bearing forward, or away from the engine. My problem has been the adjustment of the clutch cable. To get the clutch to release, I have to adjust the clutch fork to where the lower edge (below the pivot) actually rubs against the spinning pressure plate. If I tighten the clutch cable to where it doesn't rub the pressure plate, it won't release the clutch. I know I can stack or remove washers from behind the clutch fork ball pivot, to move the fork closer to or (as in my case) further away from the pressure plate. I am figuring I need at least an extra 1/4 inch away from the pressure plate. If there are not several washers stacked behind the pivot...that I can remove, my other options would seem to be to remove enough material on the back side of the fork where it contacts the pressure plate, but that would obviously weaken the fork. It has been suggested that I heat and bend the fork, but I am concerned that as it is a cast part, that too may weaken the fork. Is it possible that the fork is not correct for the trannie?

Anybody else face this problem and come up with a remedy? I would like to come up with a couple alternatives before I drop the engine and trannie.
TIA for your advice.

Speedo

[speedo]

Anybody? Free old spark plugs if you make a credible post.

Speedo

[john walker's workshop]

Sometimes that pivot ball unscrews itself. I,ve also seen bent forks.

[pors1968]

Just guess do you have part 911 116 774 01 hafl 70-71 are missing and the spring fork to trans one inche spring.Had same problem these two parts solved it.

[speedo]

Originally Posted by pors1968

Just guess do you have 911 116 77 401 hafl 70-71 are missing and the spring fork to trans one inche spring.Had same problem these two parts solved it.

What am I missing...

Speedo

[Phrog]

Look at diagram attached to spring part list. Most likely you do not have the spring and conical washer just as pors68 described.


Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

[speedo]

Top of the page...
1970 Porsche 911 T Coupe/Targa - Clutch & Flywheel - Page 4
The back lower side of the fork hits the pressure plate. I wonder if I can look up through the hole in the bell housing and see the washer and spring behind the fork?

Speedo

[speedo]

I do indeed have the conical washer and flat spring installed, behind the fork. The fork however is free to float on the ball pivot approximately 1/8th inch fore and aft. Is that play normal? I would have thought it would be held more snugly and still allow for it to pivot. Pressure plate looks normal too, although I am going to pull it off to measure the thickness of the clutch disc...on the outside chance it is too thick. Not likely, but if it were too thick, it would be harder for the fork and throwout bearing to get the pressure plate to release...maybe forcing the lower edge of the fork into the face of the pressure plate in the process?
Also noticed that the throwout bearing has a lot of fore aft movement as it is mounted in the pressure plate. Checked another engine and it was rather tight. Wonder if extra slop there could make it more difficult to get the pressure plate to release the clutch disc. At rest, the face of the pressure plate should be flat, yes? Not convex or concave?

Speedo

[Matt Monson]

Check to see if the tines on the fork are worn out and flopping around on the TO bearing.

[speedo]

The pivot bolt was not loose...just seemed like with the bolt torqued, the fork seemed a bit loose on the pivot. Problem is the opposite of the clutch package being further away, if anything seems too close. I may have discovered the problem(s): the throwout bearing has too much fore aft play and the clutch disc looks to be a slightly smaller and thicker disc. Spec book has a new disc at 8mm and mine is 9mm+. And in examining the disc, it is slightly smaller in diameter than my other discs by 10mm. Could it be a 69 clutch disc? I compared it to a new 69T disc, and it is the same thickness (9mm) and the same diameter. I am guessing a little slop on the fork pivot, coupled with a bit of wear on the throwout bearing, and a disc that was too thick...all would contribute to an over-adjustment of the clutch cable to get the fork-throwout bearing-pressure plate to release the fat disc, and the over-adjustment allowed the fork to contact the face of the pressure plate. Clutch forensics...

Speedo

[speedo]

But I would have thought thinner is better in my case. Remember the problem started with me having to "overwork" the clutch fork to get the pressure plate to release the clutch disc...resulting in the fork hitting the pressure plate. If the pressure plate released the clutch disc earlier (ie. with less fork movement), would that not be beneficial? Less movement would mean less likely to hit the pressure plate with the lower end of the fork? I am thinking back to the 69 clutch disc differences...where the S disc was thinner than the non S discs. I can remember hearing that if one were to accidently use the thicker non S disc, it would be difficult for the pressure plate to release the disc. Is this correct, or am I backwards? Spec book states 8mm plus or minus, with a wear limit of 6mm. I am thinking with the thicker 9mm disc that was in there, I need that extra 1mm...or the correct 8mm disc.
This make sense? I also have the opportunity to replace the steel pressure plate with an aluminum one...swap over the ring gear, and a tight TO bearing. Neither one looks to have been machined and I am guessing they both share the same specs so the thinner clutch disc should work with either PP?

Speedo