Crankshaft bearing question

[DEANs427]

when a crank is turned down .020 on the mains how much material is normally removed from the thrust surface on the center main? I am specificly referring to my drag car SBF but the question could also apply to an FE. I am refreshing the motor over the winter. I found crank journals and bearings like new except for rear side thrust bearing overlay wiped out with .020+ endplay. the crank surface looks fine.when measuring the thickness of the good thrust bearing side it appears that a new thrust bearing is still going to leave about .012 end play, to much for my liking. So, my question is, is there a special .020 thrust bearing with thicker trust sides? would a .030 bearing have the thicker sides, then I could work the journal surface of the bearing down to fit the crank. I want to avoid machining this nitrided, fine balanced crank that looks perfect after 750+ passes

[Ted]

The thrust portion of the crankshaft is typically only 'kissed' during the main grinding operation meaning only a minimum of material is removed.  I'm not aware of any bearings with additional thrust thickness but I have had to shim the thrust bearing in the past to reduce the amount of thrust clearance.

[XR7]

There has been some of this going on recently it seems, and mostly SBF but other engines as well. Do you have an auto or stick trans? 90+% of the time it is converter fit issues with the crank. On a stick car if you cold start with the clutch in can add wear as well. It is almost always worn on the rear face of the bearing, no matter the trans behind it.

There are "high side" tolerance thrust bearings available as well as oversize thrust bearings available that would need the journals widened with a grind to fit. Most of the time it isn't needed... especially if under .020 or so. You may have to try several thrust bearings and select fit one that will be within range. Here is a webpage talking about increased thrust bearings available.

http://kingbearings.com/maxflange_proflange.php



Here is a fix that someone has come up with for excessive thrust issues. It is a long read but get down to the bottom for an image and a cure...

http://www.4secondsflat.com/Thrust_bearing_failures.html



Also here is a longer read for the same issue, with pages of comments and advice on what to look for, mostly with an auto trans and converter issue that was the actual cause for the quick thrust wear on a SBF.

http://www.yellowbullet.com/forum/showthread.php?t=601755

Hope this helps! I think you will find that you won't need to grind the thrust on your crank, and with the bearing trick and finding the actual cause, your problem will be solved.