Bumps on Cam Bearings

I've pulled apart a number of engines that've been sitting for years. Probably 25-30 that had been sitting at least 10 years - but that bearing is different...

I'm curious to see if anyone knows what the composition of the different layers of metal are in these bearings. I'm thinking that I may do a little destructive testing on one of my bearings to see where that seperation is occuring. What if I slapped a bearing in the 'ole Bridgeport at work and carefully milled right through the middle of one of these bumps? Might be instructive to see a cross-section of the damage.

That's the worst bearing I've ever seen like that.

I've smoothed and run those old Kawasaki bearings many, many times. That particular one, I'd toss in the trash.

Most generally they will sand up just fine with used 1000G paper and be 100% problem free.

Best to wet sand in the parts tank. It's not uncommon at all for a good engine builder to get the clearance he wants on cranks bearings by using that method.

You won't trash your cams from sanding the bearings properly.

I've seen motors that had the read cam chain roller assembly put in backwards. In fact I've seen it twice. The cam chain sawed righ through the metal bracket. That's a lot of steel grit being pumped around inside the motor. There was no damage to the cam bearings in either one.

Larry, is there anything else in these motors that gets oil pressure besides the cam bearings. I just looked in my Clymer manual and it shows that the oil pressure should be 2.8 psi. Also shows that the cam bearing clearance should be less that 0.006" I'm used to car motors with bearing clearances like 0.0002" and more like 40 psi. I guess that these bearings just run more loosely?

T, It's been years (many) But If I recall correctly, plain bearings are Phosper bronze,manganeze & zinc. the ph/bronze being base, mang/zinc the "white metal". in my youth, I knew builders who routinely "polished" bearings upon install, Later education reveals this is a no-no as it yeilds no purpose but to lessen oil presure. In a perfect world, plain bearings should never see metal to metal contact. lumps are beyond my experiance, but personally I would't try to correct via sanding/polishing especially on a machine which typically only makes 3-4 lbs of oil presure. luck G