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Valve Train Replacements

Discussion in 'Intermediate CJ-5/6/7/8' started by Wrettman, Aug 2, 2019.

  1. Aug 2, 2019
    Wrettman

    Wrettman New Member

    Colorado... for now
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    There may be a thread concerning my question already, but having looked about for a while, not seeing one, here I ask:
    When pulling apart my recently aquired AMC 360, the Camshaft sustained some damage. The lobes look alright, but the bearing surface is a bit dung up. Otherwise, the valve train looks/measures to be reusable. The question is: were I to replace the camshaft, SHOULD I too replace lifters/rods/valves/etcetera as well? Or might I get away cleanly with a new camshaft alone?
     
  2. Aug 2, 2019
    sterlclan

    sterlclan Member

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    Cam and lifters should be replaced as a set. The lifters wear to each lobe. New cam +old lifters = short lifespan
     
  3. Aug 2, 2019
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
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    You must replace the lifters if you replace the cam. No alternative. You can put new lifters on an old cam, but not the reverse.
     
  4. Aug 2, 2019
    Wrettman

    Wrettman New Member

    Colorado... for now
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    Thank you
    I know every manual spells out "replace as set," but there are also some corners to be safely cut. Good to know that old lifters with a new Camshaft is not one of them. It is just unfortunate I spent a lot of time cleaning everything already :cry:
     
  5. Aug 2, 2019
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    You can replace one or two lifters on an old cam, no problem. That's an acceptable cheap repair. But with a new cam, the old lifters will chew up the new cam, as Jeff points out. Same problem if you mix up the old lifters when you remove them - you can't put them back. They wear-in to the lobes and moving them around will chew up the cam.

    If money were really tight, RockAuto has no-name lifters in a pack of 16 for $32.
     
  6. Aug 2, 2019
    53A1

    53A1 Member

    Kern Co. Ca.
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    How did the bearing surface on the cam get banged up? I wondering if you need to change the bearings in the block.
     
  7. Aug 3, 2019
    Wrettman

    Wrettman New Member

    Colorado... for now
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    I am going to change the bearings, either way. The camshaft got banged up because I am an idiot...

    With oily, greasy hands, I dropped it straight to my cement patio moments after pulling it from the block.
     
  8. Aug 3, 2019
    Chilly

    Chilly Active Member 2019 Sponsor

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    Then gravity did you a favor. No way I'd put an old cam back into an engine once I had it out. They arent terribly expensive, and are a wear item. And so many options to improve performance. Be sure to follow break-in procedure, use good assembly lube.

    Is your timing set the crappy nylon gear variety? I'd also put in a Rollmaster set if the timing set has any significant age to it. I know, more money. I have an unused Melling set (I think its a Melling) still in the box if you want a regular set for cheap. My machinist ordered it along with a bunch of other parts but I'd already purchased a Rollmaster.

    And if you go with a roller chain I recommend soaking it in solvent to get off all of the rust preventive stuff, which is NOT a lubricant, then soak in high zinc break-in oil for a couple of days.
     
    Last edited: Aug 3, 2019
  9. Aug 3, 2019
    Keys5a

    Keys5a Sponsor

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    I can't believe the camshaft didn't break when you dropped it. They are cast iron and are quite brittle. Yes, replace the camshaft, lifters, and I would replace the timing chain/gears. Unless there is a good reason, I wouldn't replace the cam bearings unless I were performing a complete rebuild. They usually are in good condition even on old engines.
    -Donny
     
  10. Aug 3, 2019
    Chilly

    Chilly Active Member 2019 Sponsor

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    Concur with reusing cam bearings. More risk of issues by changing them than by leaving them alone, in my opinion.
     
  11. Aug 3, 2019
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

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    Not disagreeing in general, but the 360 can be a special case. The 2nd/3rd gen AMC V8s (290/343/390 and 304/360/401) are known for low hot idle oil pressure at high miles. Usually this is from wear of the oil pump accompanying normal wear of the crank bearings, but instead it can be from delaminating cam bearings. Not unusual, apparently. This should be evident at close inspection, and cam bearing replacement would then be called for.
     
  12. Aug 4, 2019
    sterlclan

    sterlclan Member

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    I second the inspection of bearings in the block, mine were totally delaminated.
     

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