Correcting flywheel runout without removing engine?

[dchw1975]

Hi,

I have been having an issue with the flywheel becoming loose repeatedly. The runout is about 25 thou which I think is contributing to this. Its really quick to remove the gearbox and put it back in but a right pain to actually get the engine out and I don;t have the time before I need the car at the end of Jan for VSCC events. Is it possible to correct runout by filing the taper in the flywheel or would i have to get the engine out and remove sump etc to lock the crankshaft and then use grinding paste? If the later then would it really be so bad if I just do it up to about 150ft/lb and accept I'll have to tighten it every so often?

David

[Howard Wright]

Hi David

I thought the 15 thou flywheel runout I had on my first Special was stretching it!

You’ve got 5 weeks! If it was me I’d have the engine out and spend time trying to lap the taper. Again I think doing this on the bench and checking runout with the crank on V blocks is the way to go.

If this doesn’t appeal… Use Loctite 660 (taper lock) and put up with what is likely to be an out of balance engine  .


Cheers

Howard

[Bob Culver]

Are you sure flywheel is not contacting the bearing slinger before the taper tightens? Can remove material from end of flywheel. Flywheel may have suffered previous lapping. The fit can be checked with blue. Any step in the flywheel can be scraped off, and or end of crank bevelled. The crank runout can be determined in the car.  If the crank OK old time fitters would scrape the flywheel taper and maybe  finally lap. if the flywheel has been loose the crank may be raised around the key. A lot of lapping renders crank and flywheel non standard and likey upsets clutch operation.
Later flywheels are relieved in the centre; a technique which assists holding.
Perhaps someone can work out in gm cm sqd or whatever the dynamic unbalance of .025" represents.
For a true running flywheel static balancing acheives much. For those with a lathe and patience various jigs can be made up.
I can detect one thin clutch cover washer which is about the commercial tolerance.
Flywheel runout does not help the crank although I suppose if at the right angle might be beneficial! Curiously cranks often fail at the last rear radius

[Dave Mann]

If the flywheel is coming loose repeatedly, this can be caused by the key being too tall, check that there is clearance between the top of the key and key way.

[Bob Culver]

Daves reply could  also explain the runout. having tinkered with tapers on lawnmoers, various cars, some things go without saying!

[AustinWood]

Another reason for the flywheel coming loose is the taper being worn down. This makes the flywheel pull up on the rear main bearing instead of the taper. Check that there is clearance between flywheel and bearing.