Ok cnc-motorsports is selling a 4340 eagle crankshaft that shows it had "Mains Ground .010 By Eagle". They are selling this crank alot cheaper than the other 4340 eagle cranks. Why would they grind the mains on the crank? Is the crank weaker now that they did this? Also if I was to buy it since the mains have been grinded do I need to do something else with the engine when I get my new bearings or when I take it to the machine shop do I need to tell them about the mains be grinded or does anything at all need to be done? Thanks for any help.

 

you can get mains .010 under

 

Most likely ther were some surface imperfections on the journals so they turn it .010 and sell it cheaper. There are not really any bad side effects from this, many cranks are turned .010 all the time. You will need to order bearings that are .010 thicker to get the clearances right. The only negative is that if you have a bearing failure you might not be able to re-use the crank because they can only be ground down so much before all the hard heat treated area is ground off. Then again, even if the crank had standard journals a bearing failure might trash it completely anyways. Although I am not real happy with CNC-motorsports, I just ordered a complete forged rotating assembly from them and got the runaround for 2 months waiting for my parts.