Spun Bearing

Well, after a year of letting my CJ sit looking sad and forlorn in the bottom of my yard, I finally looked into the bottom end of my F-head to see what was causing the horrible noise it started making on its last voyage.

Low and behold, there is bearing material extruded out around the crankshaft and the conrod on the #1 cylinder. I pulled the bearing cap and sure enough, the crank journal surface is all smeared around. I pulled the rest of the caps, and the other crank journals look alright, but the bearings look somewhat suspect. I guess its off to the machine shop to get the crank re-ground. It could be worse though, I was betting on the crank being broken.

Any rough ideas on how much the machining will cost? I realize different shops charge different rates, but I just want a basic idea. The cylinders all have either 120 or 125 psi compression, is this normal? If so, I don't think I will do a full rebuild, I'll just fix the bottom end and run it as is. Any suggestions on this? Thanks

Austin


this is one bearing half from #1

http://earlycj5.com/forums/attachment.php?attachmentid=18823&stc=1&d=1184279892

http://earlycj5.com/forums/attachment.php?attachmentid=18824&stc=1&d=1184279892

this is the #1 journal

http://earlycj5.com/forums/attachment.php?attachmentid=18825&stc=1&d=1184279892

this is the #2 journal, 3 and 4 look similar

http://earlycj5.com/forums/attachment.php?attachmentid=18826&stc=1&d=1184279892

 

Hmm. If you want to try it, you can get some crocus cloth and try to polish out the bearing metal from the crank journal. The crank and rods are forged steel on a 134, and much harder than the bearing metal. Polish it up, put it together with some new bearings, and Plastigage it.

Note you cannot do this with a cast crank - they must be reground.

If I had it apart, I'd certainly change the rings and maybe grind the valves, as well as bearings. With this engine, I'd be happier if I could take it apart and clean it - but the rod bearings, rings and valves can all be done with the engine in the car. That's an old-school "overhaul."

 

Yep what Tim said, that looks like bearing material gauled to the crank not a messed up crank itself.

 

you can also soak rags in a lye/water solution and wrap the journal in them, the lye will eat teh babbitt off but leave the journal pristine.... Be careful though lye at that concentration is extremely caustic and will definitely eat body parts...

BUBBA

 

Thanks for the help, i will try polishing the crank and installing a new set of bearings and then plastigaging it. I greatly appreciate the knowledge that gets passed around here.

Austin

 

just got my crank back today $95 turned .010,.010 by the way polishing works,have first hand experience on that,and have done it on a cast crank as well,but it was in the riding lawn mower,5 years later still going strong, i use a pice of leather wraped around the crocus cloth one turn and just pull the ends of the leather,this helps avoid making any flat spots,"polishes evenly"