Am I being "Thick"?

[ianh1968]

Regards "Thin Tail" cranks and "Thick Tail" cranks,
For the benefit of the ignorant amongst us...

Would it be correct to say that:
1) The "Thin" tails were (1.3/8") and are or were originally, oil fed?
2) The "Thick" tails were (1.1/2") and were Deva bushed?

Did the same rules apply to both 850 and 997cc cranks?

Were there other size/configurations for small bore
cranks which are not either 1&3/8" or 1&1/2" and listed here?

So that we can all understand the terminology correctly,
a proper definition of "Thick" and "Thin" would be appreciated...

Ian

[R&R]

Ian,

Carrying on from the other thread, my research into the 997 engine has lead me to believe that from the start of production it was fitted with the 1 1/2" tail crankshaft. Nobody has proven otherwise to me, but that is not to say a 1 3/8" variant doesn't exist.

The variants of the 997 crank are:

12A375 which from evidence I have seen has a 1 1/12" tail and is drilled for an oil feed to the primary gear.

12A298 which from evidence I have seen has a 1 1/2" tail and is not drilled for the oil feed to the primary gear.

On 997 engines there were 4 different primary gears used, all compatible with the 1 1/2" tail crank 22A344 (DU Bush), 12A380 (oil fed bush), 22G106 and 22A551 Deva bush types.

In addition the 997 was fitted with 3 different flywheels, all for the coil spring clutch and to fit the large tail crank. 22A327 for the DU bush primary, 12A377 for the oil fed primary, and 12A527 for the DEVA bush primary.

In addition the first 60 High compression (probably home market) 997 engines were fitted with the 298 crankshaft while the rest of early 997 production was fitted with the 375 crank and oil fed primary. This I assume was to field test a self lubricating bush (DU bush) in the primary on home soil with a note in the parts book to report failure to service technical department.

After engine number 9F SAH 15632 the deva bush primary and 12A298 crankshaft were fitted for the rest of production

None of the primary components listed above, or any of the associated, bushes, thrusts etc. are listed for the early thin tail 850 engine.

So in my view the 997 engine was always of the thick variety!

Does that make it clearer?

[R&R]

http://www.ggbearings.com/en/products/metal-polymer/du

Did a bit more research and found this....

[Spider]

As I posted in the other thread (that we so rudely hi-jacked - apologies 5Ports);-

From one of the parts books I have;-

"12A375 CRANKSHAFT, bare, oil-fed bush type, 1 3/8" tail diameter 1 997cc 1961-62. Stamped no. 12A375.
12A298 CRANKSHAFT, bare, Deva bush type, 1 1/2" tail diameter 1 997cc 1962-63. Stamped no. 12A298."

I've seen and worked (a bloody long time ago now!) on 997 Thin Wet Tails and 997 Thin Dry Tails, which I think was converted from a wet tail. I've never seen a thick Tail 997 Crank, though I know they were produced.

It would also seem that 5portsrock also found much the same when you read his opening post in his thread here

viewtopic.php?f=3&t=14059

I've been using DU Bushes for many years, they are what I fit in to the Rod Shift mech when the originals wear out. Great Bush, but not the thing to use in a Primary Gear.

Ian - Yes on all accounts!

[JohnA]

This crank is out of a 997 Cooper engine number 12 and has 1" 1/2 Tail and oil feed hole.
It has not been used for over 40 years. Std bore and crank
gudgeon pin had come loose and damaged the bore and left under a bench

[Rich997]

My 997 engine apparently suffered the same fate as described by John A (gudgeon pin moved)
Extensive damage to the bore resulted which is probably why the car went off the road.

I'm on the look out for a 997 crank, rods, pistons, head and gearbox to build a spare motor.

After much deliberation I converted to Deva bush rather than preserving the original and seemingly inferior wet bush type.

[Lakeland997]

My 1962 997 had a 1 1/2 tail 'wet' crank although it had already been plugged and a deva primary gear fitted as per the BMC service fix.
It also came with a NOS crank stamped 12A375 also 1 1/2 tail and oil feed hole:
Here it is after machining and hardening. You can see the remains of the number stamping:

IMG_1143.jpg

[Lakeland997]

Incidentally, if you convert one of these cranks to the deva bush you need a special thicker backing ring that I believe came in the conversion kit because the oil-fed primary gear must have been longer and the position of the rear thrust washer slots is closer to the taper:

IMG_0061.jpg

IMG_0058.jpg

[R&R]

Interesting that engine no12 is drilled for an oil feed, do you have the primary gear from it?

Incidentally, if you convert one of these cranks to the deva bush you need a special thicker backing ring that I believe came in the conversion kit because the oil-fed primary gear must have been longer and the position of the rear thrust washer slots is closer to the taper:

That was the part I had to make for mine, but with the flywheel I used, I couldn't get the large release bearing to fit without machining the "wok" casing where the plunger goes through. I've always managed to fit this bearing with other coil spring clutches..... It worked though, so I was happy enough with it although I would have changed it had I kept the car.