Need advice on 1st engine build - cam bearing damage

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Keystone

Keystone

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I'm doing my first engine rebuild on a 5.2 Magnum that's going to replace the Slant in my '73 Swinger. Quick backstory, it's out of '96 Ram and I paid $200 for it off of Faceberg Marketplace. It was described as (of course) "running when pulled", but for the price I figured I couldn't go wrong since other than missing the alternator, it was 100% complete.

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I was hoping to just clean it up and and re-gasket a few things, but after doing a compression test, the numbers didn't look great.
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I misplaced the paper I wrote the figures on, but as I recall they were all in the 100 - 115 psi range. That seemed low, so I decided to tear it down.

Nothing jumped out at me as being out of the ordinary, except a couple of the cam bearings, which I'll get to in a minute. The cylinders were all smooth, with no noticeable crosshatch, so at the very least they'll need a hone.
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The rod bearings were showing some wear, but didn't look bad. At least I don't think they look terrible.
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Same with the crank bearings.
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And none of the bearing surfaces on the cam looked bad.
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So, what happened to these two cam bearings?
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The same bearing but from a different angle and zoomed in
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This one isn't as bad, but still messed up
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All the others seem fine.
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I have the tool and new cam bearings on order, but I want to know if there's anything else I should be looking for since I have no idea what caused this. I'm still hoping to just be able to do a hone and put in a re-ring kit. Again, this is my first rebuild, and I'm sure I'll have more questions as I move forward, but this is definitely one I'd like some input on.
 
That’s what happens when the oil pressure gets low and it starts to grab the bearing. You can see in your pictures where the cam has been grabbing the bearings.

I’d also measure the main bores and the Rod bores. They need to be round and to size.
 
Interesting... generally cam bearings hold up well and in most cases after inspection don't need replaced. =But yes oils starvation would have to be the only thing that can happen really. I n ideal conditions there should be none to very little metal to metal, contact on a cam bearing.
 
Those rod bearings are worn down to the next layer, how does the crank journals look.

I’ve had some cam bearings look like that, just replace them. The cam looks good from here.
 
I guess something else I should add is that this is just supposed to be a temporary engine of sorts. I was a little surprised to see how much it costs to convert one of these cars from /6 to V8. All new exhaust, all new cooling system, new fuel system, new trans. My plan is to (at first anyway) put in a fairly mild V8 so I can keep the 7 1/4 rear and 14" wheels/tires I'm running for the time being. Then I'll upgrade the rear, wheels, and trans as a next step. Putting in a stroker will come last. That's why I don't want to go crazy with dumping money into this engine, so I'm hoping to reuse as much as possible, like the stock cam.

Here's a picture of the crank. I can't catch a nail on anything, but I haven't mic'd it yet.
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yellow rose said:
That’s what happens when the oil pressure gets low and it starts to grab the bearing. You can see in your pictures where the cam has been grabbing the bearings.

I’d also measure the main bores and the Rod bores. They need to be round and to size.
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Ok, that makes sense. And yeah, I was thinking I should probably buy a bore gauge, so I guess I'll go ahead and get one of those too. Summit has this one that seems decent

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Forget the $200 bore gauge, hone it had run it. If you are stroking it later then why get so picky? The thing looks good. Needs some bearings is all.
 
Keystone said:
Ok, that makes sense. And yeah, I was thinking I should probably buy a bore gauge, so I guess I'll go ahead and get one of those too. Summit has this one that seems decent

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You can go on Amazon and buy a nice bore gauge for well under a hundred bucks that look just like that over priced Comp gauge.

If you are assembling engines you should have a bore gauge.
 
Temporary engine? Hone it re ring it and put a complete set of bearings in it. And a new oil pump with pick up. Done deal. Nice pictures btw I wish everyone took pics as good as you did.
 
Thanks for the replies everyone. The tool and the cam bearings (they're actually made in the USA!) showed up, and with the feedback provided, I'm comfortable to move forward. Have a great weekend.
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I gotta say, those rod bearings are not ok....

But....its likely you can do the basic rings and bearings bit and be ok. It doesn't look trashed.
 
Looks like the original owner used the oil light as a "change oil" light. Commuter or mom car, likely.

Like yellowrose said, you can get bore mics cheaper. Look for used machinist tools if possible. Pawn shops and the like often have tools like that too. Used mitutoyo or Starrett brand tools are better than cheap Chinese Amazon junk.
 
Ok, prepare yourself for the cam bearing disappointment. You buy the bearings, you buy the tool, you install the bearings with surgical precision. You step back very pleased with yourself. Not even a blemish in your new cam bearings. Start to slide the cam in............what!!!! It no fit!!!!! But but but you did everything PERFECT! Look at them!! It will break your heart to hear the solution.
 
You could try and find a talented machinist who could actually fix the cam bores, you could be one of the few lucky ones that it slides right in or you could get mid-evil on it. Like a bunch of people do. Me being one of them. You groove an old cam core lube it up and turn in as it “hones” your beautiful new bearing to the right size. Go slow and back it out and clean out the grooves frequently. Then go into the corner and weep. No sanding! It just embeds the grit into the bearing forever.
 
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