Doing some checking prior to rebuilding my original motor. The crank tail seems to have about 3 thou of runout at the taper. This seems to translate to roughly 5 thou of runout on the flywheel clutch face.

I can't seem to find a definitive tolerance anywhere.

Is 5 thou too much or should I put on an old flywheel and take a few carefully calculated whacks with a big hammer in the right spot?

Yeah, I know that sounds rough, but I'm working on the theory that the flywheel may have been whacked before to remove it so perhaps that can bend a tail a bit?

Over to you , Brains Trust.

Cheers, Pottsy

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Smile Up at The Trucks!

Pottsy, only reference I have seen on crankshaft runout is Vizard's in his big book that the factory tolerance was .003", so yours seems on the limit. I'm not sure how this translates into runout on the flywheel clutch face. You could try another flywheel on the crank and see how that compares.

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Steve

I would get a machine shop to true up the crank taper.
No way you are going to bend the crank by whacking the flywheel.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I would try lapping the flywheel. Cheap option. This may correct a thou. I reckon they would all be out. Its 50s tech after all

Thanks guys. I'm thinking that the machinist is going to get the gig. Going to see him very soon to get the block tanked.

IN regard to the runout, my main thought was in two parts.
(1) I can't find a tolerance anywhere, and can't believe that it would be expected to be true, as in 0 thou runout.

(2) I was wondering if a bit of percussive removal done in the past may have caused the bend, so was thinking of reversing the process. (It's a theory at least)

This crank has an interesting history so worth saving if I can. It's a 997 Cooper 12A298. 3.2" stroke and cross drilled. Some years ago I ran the centre main and the crank turned out to be both bent and out of phase when it came to checking it before the last rebuild. Orgers in Bayswater did a miraculous job of straightening and phasing. I never checked the crank tail before or after so it could have always been a bit out.

I'm planning on rebuilding this motor. It's bored 40 thou and with the reduced stroke the swept volume is almost exactly 1098cc. It's always been sweet, but was having overheating issues before finally blowing the head gasket last year.

Looking at hone, new rings and bearings (all assuming it all measures up OK) and maybe a Crow 607 cam. Already has a lightened flywheel balanced with the rest of the rotating bits. Running a Lindsay Siebler modified 12G202 head with extra large valves, twin SU's, 123 electronic ignition and Wildcat extractors.

Always been a spritely little beast.

Thanks for the responses so far.

Cheers, Pottsy

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Smile Up at The Trucks!

(2) I was wondering if a bit of percussive removal done in the past may have caused the bend, so was thinking of reversing the process. (It's a theory at least)

Pottsy, you Butcher!

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"Show me the Mini!"