Back when I was running the 4 speed on my duster and the friction plate blew apart it took my rear main bearing out slightly. To get back racing I just threw another rear main bearing in and ran it for 5 years until I took it apart this winter. Sent the crank in for mag and Polish and/or grind. The mag results came back and that rear main has some heat cracking. It's just in the flat, the radius is not affected. What would you guys do? I was thinking of grinding it .010 and using it. Or should I use a different crank?

hi
i would have it ground and re check for cracks .

grinding .010 onlyy removes .005 of the surface.

may have to go more to remove cracks depending on depth of cracks .

when cracks are gone it will be good as new .

In which direction is the crack? If lengthwise, you may run it. My

The cracks are going across the journal, not around it.

So you have probably ran with it for some time. Measure it, keep the records and run it! Check it next time you pull it, and compare, if it grows you need to do something. I guess it is a Bryant or Winberg crank, and they are heat treated on the surface? If you grind it the surface will be softer and less fatigue resistant.

Thanks for mentioning that. I knew but forgot about it. Will polishing remove the hardened area? I'm gonna call Winberg tomorrow and ask them now. Glad I didn't go ahead and grind it yet.

Yes, I would absolutely ask the supplier, as you have the crank number, and they have the file on metallurgy, treatment etc. and know how to treat it correctly. When cranks are that optimized there is not much margin against weakening it. I doubt polishing it will be any issue, you do not take away measurable amounts. Good luck, and keep us informed!

I will let you know what I find out. Might end up having them fix it.

IMHO that's the only way to do it. Get some money out of savings and send the crank back to Winberg with request to make it okay again.
He's one of the best crank guys on the planet, why would you entrust it to anyone else?

R.

I called Winberg and they don't do repairs. They have a guy that does it on the side if I wanted. The guy on the phone told me any good machine shop that can get it nitrided again will be fine.

So, then you know you can fix it, if needed. Great!

Yes that is great news indeed. There is a very reputable machine shop in the area that does this. Kilpatrick engine and trans. They have a state of the art machine shop.

If you want a 2nd opinion you may want to give http://www.shaftech.com/ a call.

Rod

It would be interesting to know what would cause a crack of this nature. Is it going to open up and peel away the bearing surface? Probably wouldn't notice it till it was to late with a high RPM engine that you have.