Has anyone every welded the flywheel to the crank to stop the flywheel coming off. The rest of the motor is fresh, the crank is at its final grind,and would be discarded when and if the motor was to be rebuilt again. Just sick of the flywheel coming loose on the crank and don't really want to pay for a new crank unless I have too.

Bad plan! Cracks >>>> Bits coming very loose >>>> unexpected bits leaving the car towards your crotch.

Flywheels don't `come off' the crank if they are a good fit on the taper.
Good condition tapers should be lapped together with fine paste to get (IMO) at least 75% contact area.
If they are not in good condition (metal pickup etc), fix that first, by machining or replacement.
I agree with the above, DON'T weld it on.

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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.

Three questions... and a suggestion

1. What is the condition of the tail of the crank?
2. What is the condition of the taper inside the flywheel?
3. What are you torquing it up to?


If you're torquing it up correctly and its still coming loose... there is a few possiblities.

The flywheel bolt is there to lock the flywheel on the taper... If the tapper is worn or the tail is worn to a point where the bolt is tigthening agains the end of the crank and not the flywheel, you will not be able to get enough loading on the flywheel to lock it on the taper.

Likewise, it the tail is gouged and looks like a dogs breakfast, it will not have sufficient surface area making contact with the inside taper in the flywheel....

The taper is what holds the flywheel on, not the bolt.

I would suggest, if you tail looks like crap, that you remove any high spots with a diamond lap. Then using a light smear of course valve lapping paste, lap the flywheel onto the tail. Just keep working it till it goes quiter. Then clean all the paste off. You'll be able to see clearly just how much contact there is between the tail and the flywheel (there'll be a witness mark from the paste) If is only touching it a few places, then its probably not going to get any better. If you getting 80% + contact, you my be able to lap it some more and get a better fit.
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You can weld the flywheel on if you want... I think you'll find out pretty quick why you shouldn't though

<edit> sorry Doc, you bet me to it

Darwin says do it! Win an award!

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Simon

The adventures of an owner builder in the Tallarook Ranges

Sometimes they weld themselves on. A friend was driving down the freeway and lost the No. 3 conrod cap. Bent conrod, very sudden stop and flywheel broke the offset washer, spun and welded itself to the crank. Had to cut the flywheel up to get it off.

But yeah, what they said about lapping it...

I would put the mig down and pick up the locktite and torque wrench!

Yeah, good idea, very good.

But first, I'd use a new bolt and check the thread in the crank is OK. Wind in the new bolt without the flywheel to ensure that it is smooth all the way and is not bottoming out before the flywheel is fully tightened. As others have also said ^ lap it on. Can't say I ever had one come loose.

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Hi,

check if the key washer is a smooth fit in the crank nose and in particular if the key washer ears aren't longer than the slot in the crank, putting the bolt torque against the crank instead of the flywheel.

I've seen this happen with a brand new complete engine kit from a well known UK engine builder/workshop.

Cheers
Luis