Cam Journal surface and bearing wear...

[6TIME]

I've believed for a long time that when you buy a cam for a motor it's ready to slide in and run for a long time... I'm starting to realize that this isn't always the case anymore. I recently had a fairly major cam bearing failure that left me scratching my head. I've also heard of many other similar stories. I think I've pinpointed the source of my problem which my machinist was dead certain it was... Cam journal finish quality. From the minute I brought my block with mangled bearings into the machine shop he said "Cam journal finish! Seen it too many times! We polish every cam that we install here because we don't like to see THAT coming back at us." I had never seen or heard of this issue before? So, I examined my journals on my cam that chewed up the bearings. They looked like normal cam journals on first glance, but upon closer inspection they seemed to have a slight roughness to the surface. When he gauged the surface with the profilometer he found just what he had expected, the surface roughness average or Ra that was 24-32. Clevite specs 15 max and under 10 ideal for reliable bearing service life. They polished it to a 4Ra and I reinstalled the cam on new bearings with my fingers crossed. I recently bought a Lunati 63501 for my stroker and brand new out of the box it had a strikingly similar surface to the journals of my 63500 that ate the bearings. At first glance they looked fine but upon closer inspection... No way would I run it without being polished. I can't say that every cam bearing failure was due to this particular issue, but I strongly believe that this was my problem. From what I've heard there has been some quality issues with journal finish amongst all of the big cam companies.. It's worth the extra minute or two to double check the journals before assembly, rather than tearing the motor down later with reamed out cam bearings and oil pressure issues. Again, this is a brand new cam out of the box! Check the pics and ask yourself the same question.....


Looks shiny and good to go right?




Would you run these journals on brand new bearings? Looks like sandpaper to me..

Here's some shots of a unused GM SBC Ramjet roller cam. These look quite different in comparison....