This Week's 356/912 Porsche Problem: PART 2: THE ANSWER! The Problem: The Customer had an "end play" problem on a 356 Porsche Engine: With a .035" shim in place the End Play is over 12 thou (0.012"). With a .042" shim in place, the engine SEIZED! Given that the Customer had 2 End Play Shims, one .035" the other .042", and TWO Soft Iron Gaskets, the Maestro's Experimental Procedure is: TEST 1. OK, you got Twelve Thou End Pay with the .035" shim- with the Soft Iron Gasket in place. So, try measuring the End Play with the .035" shim withOUT the Soft Iron Gasket in place! (No, we won't put it together this way- we're doing an Experiment here!) Since the Soft Iron Gasket is .004-.005" thick, leaving it OUT should REDUCE the end play from .012" to maybe .007-.008. It's the equivalent of making the .035" shim "thicker" by .004", about equal to a .039" shim. TEST 2. Since the .042" shim SEIZES the engine, try putting an EXTRA Soft Iron Gasket between the Crank & Flywheel when using the 0.042" shim. TWO soft Iron Gaskets makes the .042" shim into a .038" shim. The Maestro figured the results of these two Experiments oughta be Interesting. Were They! They were: 1. With the .035" shim an NO Soft Iron Gasket, the End Play was STILL .012". 2. And with the .042" shim and TWO Soft Iron Gaskets, the engine still Seized! So, what was wrong? And Why? Just then the Light Bulb clicked on in the Maestro's somewhat twisted brain. "OK," said he. "So now you have a SEIZED engine with the .042" shim and TWO Soft Iron Gaskets. This is gonna sound Crazy- but go back to the Engine and see ifin there's any End Play NOW! (Aside: clearly, Under Normal Circumstances, an engine seized from too thick an End Play shim will have, obviously, Zero end play! But this is not a Normal Circumstance.) The Customer, albeit reluctantly, went back to check the End Play on the Seized engine. On the phone, the Maestro could hear the pitter-patter of big work boots walking out to the engine. Followed by a pregnant pause. Followed by the RAPID pitter-patter of work boots RUNNING back to the phone! Excitedly, the Customer told the Maestro: "Maestro, Maestro, said the Customer. "You won't believe what I found!" "The Seized engine STILL has "end play", huh?" said the Maestro. "Why that's Amazing! Yes! The "seized" engine still has Twelve Thou End Play!" "That's too bad," said the Maestro. "Why?, said the Customer, now apprehensive. "Is having 12 thou end play on a seized engine bad?" "Yes," said the Maestro. "What your measurements show is that the Flywheel Main Bearing is "walking"- moving back and forth axially in the case. Your problem is that the Flywheel Main Bearing has a worn Thrust Surface and the whole locked assembly of Flywheel, Crank and Bearing are clunking back and forth in the Case as a unit. The "End Play" you measured on your "seized" engine is how much the Thrust Surface of the Flywheel Main Bearing has been worn! About twelve thou, I'd say! And... the fact that the FWM Bearing's Thrust surface is worn usually means that the bearing is loose in the case- and that the case really needs an Align Bore. But if the Bearing gets REALLY loose, it'll pound the SIDE of the Case badly enough that Align Bore Bearings won't be tight in the case and the problem will repeat itself again and again. Ad infinitum. If the Case does have a worn Thrust Surface, it can be welded up and the Thrust recut (messy and stress-inducing). Or, if one can obtain a FWM bearing with an "Oversize Thrust" (A thicker thrust flange on the FWM), then one can trim the case and cut the Bearing's thrust to fit the trimmed case. And there you are. Until the next overhaul. Oh, but there's only one minor problem with obtaining an Oversize Thrust Flywheel Main Bearing- Porsche never made 'em! "So how can I get one if the Factory never made one???" "The Good News is that Volkswagen DID make a FWM with the needed oversize thrust. The Bad News is that these VW Bearings were only available in Align Bore sizes! But weren't VW and Porsche Case sizes DIFFERENT? Yes. The VW has a Case Bore of 60.00mm. Porsches have a Case Bore of 60.24mm, a silly quarter millimeter larger. (The Maestro thinks that, In The Beginning, when Porsche used VW 36 HP Cases that Porsche either: (A.) didn't really trust VW's Align Boring, or (B.) (more likely), took VW's rejected Cases and rebored them THEIR way! Hence, the silly little quarter millimeter difference- and the reason why 2-Piece Porsche Cases can NOT use Standard O.D. VW 36HP Bearings, despite the assertions of many a VW mechanic.) Anyhow, VW Align Bore Bearings go in steps of 0.5mm thanks to their more easily deformed Magnesium Cases. Porsche 356/912 Align Bore sizes go in steps of 0.25mm, thanks to the much stronger Luftwaffe Aluminum used in all 3-Piece Porsche Cases. The Good News is that, by a Fortuitous Coincidence, First Over VW (60.00mm+0.50mm= 60.5mm) is essentially the same as 1st Over Porsche (60.24mm+0.25mm=60.49mm). (Note, however that this is NOT true for Second Oversize! Second Over Porsche (60.24mm+0.50mm=60.74mm) does not equal Second Over VW (60.00mm+1.00mm=61mm). Second Over Porsche is a Nowhere Land Oversize.) However, THIRD over Porsche (60.24+0.75=60.99mm) is the same as 2nd over VW (60.0mm+1.0mm=61.00mm).) But Engines built with Third Over Cases never seem to run well for very long. Anyhow, do we have a WINNER??? YES! Congratulations to John Butler, who got it right! Said that the Problem was the Flywheel Main Bearing moving in the case. And who won a Spec Book! Stay Tuned for the next Quiz: How many miles will a 356 go with ALL four "Soft Plugs" missing from the Crankshaft? And: KEEP THE 356/912 FAITH!