Cam bearing issue

Small Block Mopar Engine

  1. PredaFran

    PredaFran Well-Known Member

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    While the second oil change in the engine I finished building recently, I noticed some non-ferrous particles in the oil. After a teardown, I saw some pretty aggressive irregular wear(all the bears have it but it's more prominent in the front ones). only happening at the bottom of the bearing bore. The cam was pretty tight as it came out but it had 0 wear or damage, it looks immaculate. This is a new cam I had made from Oregon cams for this build, LA-based so it would have the head oiling holes. installing cam bearings and checking clearance was the only part I wasn't able to do(was getting ready to move from CA to FL) I had the local machine shop do it. I'm not sure of the cause of this but I don't have the same arsenal of precision measurement tools that I had back in CA. I would appreciate it if you guys could give me some advice and how to approach this situation the right way. these are my theories so far
    • Cam journals are too big, they need to be ground down
    • Cam could be out of round
    • Cam tunnel could need a line hone due to misalignment of bearing journals and/or journal size issues
    I'm leaning towards the first one since the cam bearings that came from the engine originally didn't have any unusual wear. I know I'm probably gonna get grilled for not checking that part of the build myself but I've accepted it's a mistake on my end and it's a learning experience that I'm thankful I was able to catch before it caused more damage.

    I'm hopeful a quick trip to the machine shop and another deep clean of the block with soap and warm water will put me in the right track again
    Thanks in advance for the help
    Edit: Forgot to add this is a magnum 5.9l block, but it has the head oiling holes in it.

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    Last edited: Apr 10, 2021
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    • 12many

      12many Well-Known Member

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      Very soft (too soft IMO) Babbitt overlay on the bearings for one. I’d be upgrading to some other type with higher load carrying bearings other than the standard replacement type which seems to be the norm. The cam is obviously being pushed downwards from spring pressure as the lobes open the valves. Crankshaft driving the timing chain and cam. And if you’re running a chain tensioner that adds to it. Quantity of proper oiling to the journals can’t be overlooked. Someone can explain it better/ correctly/ accurately but I saw similar with my cam swap I did recently. And they are very soft Babbitt, more with the forward bearings, but still acceptable. I’m running a tensioner also. I’d look into higher load carrying bearings next time. A quick search will yield a few articles on the matter. Here’s just a sample: Cam Bearing Selection and Installation
       
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      • PredaFran

        PredaFran Well-Known Member

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        i am running a tensioner and a roller cam, im thinking of getting dura bond PDP-25 bearings for the rebuild (or PDP-16 not sure if there's a difference between them, but i do have a magnum block, just with an LA cam) I didn't think of this before so I thank you for this comment
         
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        • RustyRatRod

          RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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          Almost looks like a lack of oil issue.
           
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          • 80fbody

            80fbody Well-Known Member

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            If the cam is tight in the bore, I’d say the shop didn’t size the bores after installing the new bearings. My shop makes me give them a cam so they can test fit it.
             
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            • PredaFran

              PredaFran Well-Known Member

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              I wasn't aware cam bores needed sizing. is it common?


              wouldn't i find it present in other places too then? or not necessarily. because the main and rod bearings had no issue whatsoever
               
            • 80fbody

              80fbody Well-Known Member

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              The bearings need to be “sized” sometimes after getting pounded in. If the cam’s tight it’s a dead giveaway.
               
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              • 12many

                12many Well-Known Member

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                Sliding the cam in when assembling, sliding it out on tear down. How does it go in with no issues and then come out tight? Or did it go in tight also? How can the wear only be showing on the lower part of the bearings? Babbitt deformation on the lower part of the bearing and then trying to slide the cam out as the journals hang up on the remaining Babbitt material on the forward edges of the bearings, is that what you encountered as you tried to slide it out?
                 
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                • PredaFran

                  PredaFran Well-Known Member

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                  it definitely wasn't loose I can tell you that. I thought it was fine but this was my first engine build so it seems my intuition was off. no material was pulled out when the cam was removed.
                   
                • 72DMag

                  72DMag Well-Known Member

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                  How would they size the cam bearings? That's new to me.

                  OP I saw in your add it's a magnum block and an LA cam. technically there are 2 different part numbers for cam bearings between an la and a magnum block. The magnum cam bearings are slightly thinner. They should be the same ID (from what I have read online) but I'm wondering if this could be a possible cause for your issue...
                   
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                  • PredaFran

                    PredaFran Well-Known Member

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                    I was trying to look for this info on the cam bearing size between the PDP-25 and PDP-16 bearings. to see if that would be the issue. cause I did use LA engine cam bearings on my engine. do you know if they still have the oiling holes?
                     
                  • 72DMag

                    72DMag Well-Known Member

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                    @PredaFran It's been a couple years or more but there was a thread on here about the cam bearings. I believe the consensus was that they are exactly the same, oil holes and ID etc, but the width were different in that the magnum cam had slightly small width bearings.

                    Don't quote me on this though... I think I had photos saved somehwere showing the difference between the 2 sets.
                     
                  • 80fbody

                    80fbody Well-Known Member

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                    Not sure how my shop does mine. I’ll have to ask. You can take an old cam, cut grooves in the journals at a 45 degree angle with a die grinder and “ream” them at home. Haven’t had to myself but I’d do it in a heartbeat if I needed to instead of dropping the block back off.
                     
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                    • PredaFran

                      PredaFran Well-Known Member

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                      Is this something that's common? I don't know how comfortable I am with cutting my bearings lol.
                      It's just a scary thought
                       
                    • Krooser

                      Krooser Reform School Graduate

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                      Not uncommon to need to scrape bearings to get the size correct. Seems Mopars are more suspect than some other makes.

                      I used to have a "bearing scraper" knife I got from an older mechanic years ago. Before insert bearings were invented machine shops poured babbit bearings then may have line bored them then finished sizing them with a scraper. Crude but it's the way it was done.
                       
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                      • jos51700

                        jos51700 Hemi Orange you glad it isn't a political avatar?

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                        ALL Chrysler cam bearings go in undersized. The factory then line reams them to final size.

                        That's why you shouldn't replace them unless you absolutely must.
                         
                      • 80fbody

                        80fbody Well-Known Member

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                        "That's why you shouldn't replace them unless you absolutely must.[/QUOTE]

                        That's just silly advice unless your building garbage. Anytime I take a block in, it's tanked, magged and gets new cam bearings. Never had an issue in my 30 years of screwing with cars. If the cams tight and you're not comfortable re-sizing, just have the shop do it. Better yet, before you pickup your block, give them your cam like I do, and it'll be ready to go once you wash it up.
                         
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                        • beanhead

                          beanhead Well-Known Member

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                          Hard to tell....but those are 'burns' on the bearings, right? Not just some dirty oil sitting there?
                          How did the crank bearings look?

                          On the bright side...good thing they did't grab and spin in the bores.
                           
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                          • Bewy

                            Bewy Well-Known Member

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                            I removed the cam brgs from a 440 I am building. Looks like the brgs were installed by a previous owner, but the engine was never run. Two cams tested were tight. After removing the brgs, #3 is tight on the cam, but nothing obvious on the brg as to the cause.
                             
                          • 80fbody

                            80fbody Well-Known Member

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                            So most likely that bore is a little tight or out of shape, line, etc. Just needs a little love next time before final assembly. Personally, I would try to ream by cutting an old cam to see if that cleans it up. Then you have a plan once the bearings are changed. I wouldn't mess with the bores unless it's really off line.
                             
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                            • yellow rose

                              yellow rose Overnight Sensation FABO Gold Member

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                              ^^^^^^THIS^^^^^.

                              The blocks move around. Nothing you can do about that. AFAIK there are no oversized cam bearings out there for Chrysler stuff. You can’t hone the cam tunnel on a Chrysler because every bearing is a different size.

                              You can line bore the cam tunnel. But where will you get oversized cam bearings?????? Take a bearing scraper and carve some off the bearing until the cam turns freely and send it.
                               
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                              • PredaFran

                                PredaFran Well-Known Member

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                                crank bearings look good, and yeah its not oil sitting there, there is some oil sitting in some of those but for example the first one is just a clean bearing.
                                 
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                                • PredaFran

                                  PredaFran Well-Known Member

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                                  but then for example on the Chrysler FSM i have for the year 1973 they dont mention anything about that when they go over replacing cam bearings. and i would assume they would include something like this
                                   
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