The Maestro's Quiz 11 July 1996 It was a Typically Beautiful July Day in Sambo Se, in the Year of Our Ford, 1996. The Maestro was a-Concoursing his Pristine 1969 Shevrolay Peek-Up Truck when the phone rang. It was a phone call came from a 912 Owner in Need. And a 912 Owner in Need is, indeed, in NEED! "Oh, Maestro said the Voice on the Phone (VOP). "I fear I have a problem that I fear only YOU can solve. Could you help me? PLEASE! "Yes, my son, that is why we are here at the business end of (408) 727-1864. To solve your insoluble Porsche Problems. What be YOUR problem?" "Well, I just changed out my Clutch Disk, Pressure Plate and Throw-Out bearing in my 1967 912 and I've got this really weird problem. Everything was OK until I tried to let OUT the clutch pedal, Then there was a horrible screech!" Horrible screech, thought the Maestro instantly bringing up the file on clutch-related Horrible Screeches. Most clutch screeches are associated with 356B 180mm Clutch Disks whose springs or rivets hit the inside of the 180mm Pressure Plate. Other screeches are from a mis-matched pressure plate/Throw-out bearing combo- like using a VERBOTEN combo of a 356A VW Throw Out bearing with a 356B pressure plate. But with a 912, all the pressure plates are the SAME! So how could there be a Horrible screech when the clutch pedal was let OUT? That's Part 1 of the Quiz: What was the Horrible Screech??? The Maestro's Quiz, Part 2: What was the Horrible Screech that happened when the 912 Owner let out his clutch pedal? Well, when the guy pulled the engine out a SECOND time he found that the Clutch Operating Fork was HITTING the Pressure Plate right at the outside circumference of the "bulge". THAT was causing the screech. "The Clutch operating fork was HITTING the outside circumference of the Pressure Plate???!!! Thought the Maestro's Center of Higher Reasoning: "I've NEVER seen that before!" "Tell me my son, is the Pressure Plate truly a 912?" "Yes, Maestro. I compared it with the old 912 pressure plate- it's identical." "And the Clutch disk? Is it a Real 912 too?" asked the Maestro. "Yep I eyeballed the Clutch Disk too- and it's identical to my old one." "And what else has been CHANGED?" asked the Maestro. "Did you have your flywheel machined?" "Yep," said the VOP. "And before you ask- the Flywheel Depth was set just as your Books say- 22.5mm (0.886") for the 912." "Hummmh," said the Maestro, now locked in Deep Thought, his somewhat twisted brain doing teraflops. "And," continued the Maestro. "The Throw Out Bearing IS a 912 type, with the "ears" being large dowel pins that appeared to be "pressed" into the Throw-out bearing, not say a 356B or C?" "No," said the VOP somewhat disgusted. "It really IS a 912 Throw-out bearing. I'm certain of that. I've even replaced the Plastic pieces that fit over the "ears" of the bearing. And I've replaced the Plastic bushing in the center of the clutch fork too." "Humnmnh," thought the Maestro, now teraflopping about madly. "You're right- this really IS a Unique Problem." "Yes," said the VOP. "That 's why I'm calling you. Got any ideas?" That's Part 2 of the Quiz: What was the CAUSE of the Clutch Fork hitting the outside circumference of the 912's Pressure Plate??? The Maestro's Quiz- the Answer! So, what was the CAUSE of the 912's Clutch Fork hitting the Pressure Plate??? The Maestro, now on the spot, hadda come up with SOMETHING fast, hopefully the right answer! So he reviewed the Facts of the Case. "Let me get this straight- the 912's Clutch Operating Fork is HITTING the bulge at the outside circumference of the 912's Pressure plate and making a horrible shriek? Tell me, does the clutch work at all?" "Yes- with the clutch pedal "down", I can shift into ANY gear including reverse, but as I let the clutch out, the horrible Banshee-like shrieking starts! When I took the engine out for the SECOND time, I noticed that the clutch fork was HITTING the bulge at the outside circumference of the Pressure plate. What I want to know is WHY the fork is hitting the pressure plate." "Well," said the Maestro. "Is the clutch fork BENT??" "No Maestro- the Clutch Fork is as straight as a Fon De Luc Highway. That's not the Problem." "Did you replace the little plastic bushing in the clutch operating fork?" asked the Maestro. "Why that's amazing- YES I replaced it!" "Are you sure the plastic bushing is fully seated in the hole in the clutch operating arm?" "Well, pretty sure." "OK, and did you noticed ifin the Fulcrum Ball that the Clutch Operating Fork pivots on was SHIMMED with a washer or two underneath it?" "Geez," said the VOP. "I gave it a quick eyeball, but I didn't really check it in great detail. What's the big deal with having a washer under the fulcrum ball?" "Because," explained the Maestro patiently. "Ifin you machine a 912 flywheel a whole BUNCH you'll find that the clutch cable cannot be tightened enough to get the clutch to work. And the transmission will CLASH when you try to engage a gear. What happens is that the clutch fork will hit the transmission before the throw out bearing can disengage the clutch." "So the Trick Hot Setup here is to SHIM the Fulcrum Ball with a washer to space it out a bit. That way the Throw Out bearing comes closer to the Pressure Plate/Flywheel and allows the clutch cable to be adjustable without the fork exceeding its confinement limits and hitting the transmission. In your case, perhaps someone had shimmed the Fulcrum Ball a bit too much. This means of course, that you gotta PULL THE ENGINE AGAIN!" AARRRRGGGGHHH! shouted the guy on them phone. I've already pulled this damn engine TWICE! "Yes," said the Maestro, "But the Third Time's The Charm! Besides, my son, you've got no choice. Something is Very Wrong Inside. And you gotta find out why." The Guy groaned again, but said he'd pull the Engine and promised to let the Maestro know what happened. The Maestro went back to his Herculean Task of Concoursing his peek-up truck so that Mrs. Maestro would find it acceptable enough to sit her royal Heiness therein for a two-thousand-mile VACATION! (The first one in two years.) Finally, the day was done, and the Maestro could retire to his humble abode, close the Ten Ton Titanium doors, open a Brewski and watch the San Francisco Giants (whata misnomer) lose yet another baseball game. He had the top offa the beer when the phone that follows him around rang. "Maestro here (well, he was almost there- the beer was just about at his sweet lips). "Maestro!" yelled the VOP. "I'm the guy with the 912 with the weird Clutch Problem. Remember?" "Remember? Of course I Remember. How could I forget? It was only a couple of hours ago. I don't have Alzheimer's ... yet." "And Maestro- It's AMAZING! You were RIGHT! The Fulcrum Ball was shimmed with not one, not two, but THREE thick washers! Almost 3/16" of washers! I should have noticed it before!" "Well, said the Maestro. That's not so Amazing. But what you have is yet another example of the Truism: Ifin Some is Good, More is Better and TOO MUCH is Just Enough!" Having THREE thick washers under the Fulcrum Ball may have worked OK with some wildly machined Flywheel, but once the Flywheel had been replaced, the wildly shimmed Fulcrum ball was moved much too close and HIT the flywheel when the clutch pedal was let out. "So, said the Maestro. There was something you weren't telling me when we were we discussing the problem. You had CHANGED ENGINES!" "Why That's AMAZING, Maestro!" said the VOP. "You're absolutely right! I DID change engines. I took the old engine out, and put in ANOTHER 912 engine in, on which I had installed the new pressure plate, disk and Throw-out bearing." Yes, my son, you did. And I bet the OLD engine has a Flywheel that's Down for the Last Time or worse- machined a whole bunch, which is why the OLD engine worked with the wildly shimmed fulcrum ball but the NEW engine with a decent flywheel DIDN'T work! It is the way of all things Murphy. When you change something drastically to make something that's wrong work, when you put something that's RIGHT back in, it won't work! That's Murphy. And that's when you gotta: KEEP THE 356/912 FAITH!