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Author Topic: Postwar flywheel on prewar engine?  (Read 1236 times)

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Offline Ted

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Postwar flywheel on prewar engine?
« on: July 22, 2013, 03:07:39 PM »
What is your opinion, is there any reason not to use a postwar flywheel on a prewar engine? I think they are the same externally - the engine blocks are the same, the gear boxes are interchangeable. Just the clutch disk diameter is increased by 2 cm /a little less than 2 cm/, but it does not change the measures of the flywheel. Probably just makes it a bit lighter in weight? How about the balance problem? Thanks for your ideas!  :)

Offline John Ellis

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Re: Postwar flywheel on prewar engine?
« Reply #1 on: July 22, 2013, 04:13:32 PM »
I don't know that they are the same.  Here are some post-war flywheel statistics

ring rear teeth = 92
flywheel weight = 11.2 Kg
bolthole circle diameter = 95 mm
flywheel outside diameter = 288 mm
flywheel depth = 56 mm

The pre-war and post-war transmissions are not the same except for the early postwar 170V.  The pre-war had a one piece bell housing & transmission case where the post-war models other than the 170V had a separate bell housing.  Could that account for the 2 cm clutch difference?
John Ellis
1953 170Vb
1958 190
2007 Porsche Cayman

Offline Ted

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Re: Postwar flywheel on prewar engine?
« Reply #2 on: July 22, 2013, 04:54:51 PM »
Yes, the postwar transmissions are different, for the detached aluminum bell. But seems all the measures and mounts are the same, as it is very often to see a prewar car with a later gearbox. Just a few days examined one - the box was just put on the prewar engine.

I examined the two flywheels - the difference is only in the wall thickness. I mean the internal diameter, where the clutch disk resides, is larger. Outside it is all the same. Tried to measure the weight of the prewar flywheel. It is something like 11,3 kg, but the measuring was far from accurate.

The prewar flywheel has 89 teeth. The postwar wheels - I have one with 89 teeth and one with 92. the one with 89 teeth is all the same like the prewar, just the clutch diameter is the bigger one. The flywheel with the 92 teeth  is from a diesel  om636 and not only the teeth are different number, but the ring with the teeth is slightly different - but otherwise it is quite the same like the other two.