I have the GM Forged crank in my car, and just had it cleaned up and polished by a very reputable crank shop in my area (Moldex Crankshaft in Dearborn Heights, MI). I am having trouble finding bearings that fit the needs of the crankshaft. The crank is undercut .030" on the mains and .020" on the rods. Was also told that the bearings need to be chamfered. The rod bearings are no problem, but I am having trouble finding a "race" or "high performance" bearing for the .030" undercut on the mains. Any help would be appreciated.

 

Most cranks don't get turned .030 under but I think you can get race bearings from Summit, Jegs, or Northern Automotive for your application.

 

Yeah I figured that .030 was kinda much, and the guy at Moldex that I dealt with didn't think that it needed that much just by looking at it, but he didn't do the work so he doesn't know for sure. Either way, Summit and Jegs both don't have race bearings for .030" under, only for up to .020". Where is this Northern Automotive you speak of, I'll have to look into them.

 

The smaller the journal is, it will have to carry more load over a smaller surface area. It also incresses the heat generated from the increased roatational [sp?] speed.
A larger journal will rotate at a slower rate than the smaller.
Stay away from bearing spacers also.

I'd sell the crank and get another if it was me or at least look into welding up the .030 and turning it .010 if your stuck on keeping it.

 

http://www.northernautoparts.com/

I looked on several websites and I couldn't find any "race" .030 under bearings because I don't think anyone would put a lot of load on a crank that has been ground that much, I agree that if I were in your position I would get a new crank. call the machine shop who ground the crank and ask them why they ground so much off and where they reccomend for bearings. I have never used a crank more than .020 under which is why I said it was rare, unless the crank was badly scored or machined before it shouldn't have needed more than .010-0.20 under, most cranks can get by with a good polishing, take Hot Rod Hawks advice. Good luck.

 

The crank was already .010" under when I took it in. It was only supposed to get another .010" taken off of it cause it really didn't look that bad. Somehow when I picked it up it says it has .030" total taken off instead of .020" total. The reason I was looking to keep this crank was because I really didn't want to disassemble the whole shortblock and have it machined and balanced and such. The rods and pistons are fine, cylinder walls look good, was just not going to touch the bottom end until we pulled a main cap at the last minute and found bearing wear. So basically what you're saying Jeff is that I'm screwed both in that I paid good money for Moldex to work on the crank (crank was nitrided and leakers drilled, etc.) plus the fact that I'm looking at a new crank and all the associated machinework? *shrug*

 

Jim,
Sorry to hear your in such a position.
If your initial paperwork/agreement was to have .010 taken off for
a total of .020.
Make the company responsible for :
1. Finding bearings that will work
2. Repair/replace crank to work with your other components.
Good luck
Kevin

 

Kevin,
The guy I dealt with there said that the original paperwork said .020". What I'm thinking was that there was a misinterpretation in that the guy writing it wanted it ground down to .020" and the machinist ground off .020". I'm gonna go over there again today and discuss the situation with them. We already planned on making them responsible for those things. We'll see if it works. Either way, new crank means new machinework/balancing/mooooooore time.

 

sorry to hear that Jim! i am sure you'll get it straightened out !