Used cam to “scrape” new cam bearings

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CheapnNasty

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I’ve read multiple times the big blocks can be a bit of a pain fitting cams with new bearings. Today I used the original 400 cam to test fit. Was a bit tight, to the point of needing a ratchet to turn it and back it out. I cut grooves in the old cam journals and used that to “size” my new bearings. I hope I’m not overthinking this and just being overly cautious but of course there were high spots that became shiny, and what seems like specs embedded in the bearings. I can’t feel the specs, the bearings seem smooth. At this point with the cam lubed I can spin it with a drill and walk it back and forth, so it seems to spin beautifully. If I need new cam bearings I’m totally ok with that, I’ve never had to do this before but it’s my first big block build and just haven’t ran into this in the past. Tightest bearing and worst looking one is the rear. Obviously grooved is front.Pics attached, opinions?

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I don't know if I would try to refurbish old bearings but many shops use a old cam to make newly bearings happier. They grind a groove in the bearings to act as a reamer.
 
Probably wouldn't hurt to go over the bearings with a scotch brite pad.
 
RustyRatRod said:
Probably wouldn't hurt to go over the bearings with a scotch brite pad.
Click to expand...

But use cheap *** Dollar store ones, because real ones have abrasive in the plastic fibers and could lead to trouble unless everything gets a major douching afterwards.
I think it's usually alum oxide and its so fine that it can get through oil filters and stuff.
At least that's what I've been told a whole bunch, no clue how true but I've always avoided 3m and scotchbrite in the shop because of it.
 
As stated above ^^^.

I give the bearings a final polish with a clean Viva paper towel, that shines them up a bit.

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It’s at least a relief to see you grooved the cam same as I did. At first I turned it by ratchet, then as the new bearings eased up I used the drill. Spins nice now, I’ll touch the bearings up with some cheap scotchbrite tomorrow and see how they look. I work at a body shop so I’ll avoid the 3m stuff we use I’m sure it’s got alum oxide. I had koffels do the machine work and pop in these new cam bearings, unfortunately I didn’t have the cam I want to use at the time so scott koffel said they sometimes can need fitted, and he was right. On that rear that looks the worst of all, is it a big deal if the Babbitt layer is as it appears? Hopefully the scotchbrite eases my visual nerves.
 
Here is what a nasty 50 year old cam bearing looks like.

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You probably want to polish up your new cam bearings to get that black residue (from the fitting turning) off the bearing face so they don't look so bad.

See what is left behind after you clean them up. Remember you want a nice smooth surface left behind to float a .002 ths film of oil on to protect the cam journals as they are rotating.

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CheapnNasty said:
I’ve read multiple times the big blocks can be a bit of a pain fitting cams with new bearings. Today I used the original 400 cam to test fit. Was a bit tight, to the point of needing a ratchet to turn it and back it out. I cut grooves in the old cam journals and used that to “size” my new bearings. I hope I’m not overthinking this and just being overly cautious but of course there were high spots that became shiny, and what seems like specs embedded in the bearings. I can’t feel the specs, the bearings seem smooth. At this point with the cam lubed I can spin it with a drill and walk it back and forth, so it seems to spin beautifully. If I need new cam bearings I’m totally ok with that, I’ve never had to do this before but it’s my first big block build and just haven’t ran into this in the past. Tightest bearing and worst looking one is the rear. Obviously grooved is front.Pics attached, opinions?

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Click to expand...
Yeah that's just the way **** goes sometimes. We have to do that at work sometimes, unfortunately some blocks just don't like cam bearings lol
I will say there's nothing wrong with it. Not pretty but if the cam spins freely I'd say you done good.
Deburr the oiling holes and run a brush through carefully so when you're pulling it up another burr doesn't raise. also like said before use some scotch Brite with WD-40 so you don't imbed abrasive into the soft top layer (babbit?)
 
Back in the '70's we ran into some 440 engines that had an undersized rear cam journal in the block. The factory cam would spin fine, but when replacing the cam bearings the bearing would "squish" down undersize, and you couldn't get the cam in. The factory had used a special size rear cam bearing to "work" around the problem. What we would do was to hone the cam journal in the block to the correct size to accept the regular size replacement bearings.
 
I used the cam that came out, and before the bearings were replaced they all had good wear patterns so at least in this block the cam fit before… update after a light cleaning with atf soaked scotchbrite maroon they look totally different. Literally a few wipes and it was nearly gone. The pictured bearing is that nasty looking one from before. No worries about contamination I still have to check and possibly grind for rod to block clearance.

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