m20 crank sprocket, on m52 crank need to modify or should slip on?

[SkiFree]

Metric Mechanic sell them, as does Ireland Engineering (you'd need to email though, it's not on the general website). There was also a fellow selling them some time ago in the r3v classifieds (you'd need to google search).

[zaq123]

You'll need to cut the stepped section off the conical washer because the crank snout is a little too long. Also the m20 crank bolt is too long. The m52b28 one is shorter and works.

I've seen a detail/ drawing for this work but can't find it now. Shouldve saved it. Anyone has it or can confirm the exact measurements for machining that washer?

[digger]

Had some junk parts laying around so assembled onto m52b28 crank

BOLT:



24V crank bolt is: 95mm Under Head Length (UHL)
M20 crank bolt is: 65mm UHL

so the bolt is 30mm longer

you cant get even a single thread with the m20 bolt

WASHER:

when you push gear on there is a 2.85mm step (i.e. the snout is 2.85mm recessed below gear face) so the step on the washer would need to be approx 1.5mm to ensure that the bolt pushes on the gear rather than bottoming out on the snout.



the stock washer has step 3.4mm long

i have a washer supplied by Metric mechanic they reduced the step to 0.9mm so machined 2.5mm off it, but you could reduce it by less.



Of course check when the time comes as there could be some small differences in the spacer length or gear overall length or snout length with alternate cranks to the m52b28.

[zaq123]

thank you sir. Does anyone know if M52 crank journals are treated? Will it respond ok to some cleaning/polishing or minor grinding if needed? Or it's recommended to find Crank that's close to new condition?

[SkiFree]

Treated? Yes.

If you grind you need to nitride the crank. If you do a light polish, you should be ok.

[digger]

i would look to get a crank that doesn't need more than a polish only, except in rare circumstances i might consider getting it ground to the next size and re-nitrided.

[mikerob97]

I have a crank spacer and a set of 2.7 liter connecting rods available. I purchased for do do a 2.8 liter stoker build on my 325i, but never got to it. PM me if interested.

[zaq123]

thanks for the offer but I have too many parts as it is: extra cranks, connecting rods, pistons
need to start selling parts myself soon.

i would look to get a crank that doesn't need more than a polish only, except in rare circumstances i might consider getting it ground to the next size and re-nitrided.

I don't think cranks I got need grinding, they look very good for their age. Maybe very light cleaning/polishing if anything.