5 replies to this topic

[Chris.C]

Hi,

I think I have a problem with the crankshaft, basically the end of it appears to be 'pitted',
(the bit where the flywheel goes on that is) and according to mini magazines etc it says that
this is a bad thing.
Does this mean that I'm best off getting a new crank altogether or can I just use this one again anyway.

(I'm rebuilding a 1275 and need to keep things as cheap as possible - I'm a student!)

Picture is attached if it helps, cheers.

Attached Files

•  DSC00268.JPG   29.07K   16 downloads

[Ouster]

You may be able to use it again, but I'd be concerned about what caused it in the first place.

[pantera2075]

That looks to me like a bad casting in the first place, or, it's been scored in the past, then filler welded and re-machined. If it's always been like that then it'll likely be ok. If it's been welded, you have no idea if it has been re-hardened, and you don't want the flywheel falling off at 5000rpm right next to your feet.....

[Ethel]

http://www.epi-eng.c...g_corrosion.htm

If that's all of it I'd say the crank is reusable. Fettle any high spots it with a fine file and use some valve grinding compound to improve the fit between the crank and fly

[mr_apples]

i agree with ethel, if its for a standard rebuild

if your looking to up the power i would look for a new crank

Edited by mr_apples, 28 May 2008 - 02:38 PM.

[dklawson]

It doesn't look like corrosion to me. It looks like fretting and galling. That's real easy to produce with a loose joint. In this case, probably a flywheel that wasn't torqued up properly.

Use a VERY fine tooth file to remove the high spots. Likewise, look at the inside of the flywheel bore and carefully remove any material transferred to that surface. Then take the flywheel bore and coat it with valve lapping compound. Gently work the flywheel back and forth on the crank taper. Stop when you've produced a light, matte finish on the taper and the bore of the flywheel. Do this the minimum amount as possible to get the matte finish. Do not take off any more than necessary as 0.001" off the diameters will move the flywheel 0.007" toward the block.

Lapping is OK as long as you don't take off too much material. The pitting you've got should not interfere with safe operation as long as this is a street engine. I would not use the crank (or probably the old flywheel) on a car that's bound for the track.