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454 Worn Cam Diagnosis, what did I miss?

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  • 454 Worn Cam Diagnosis, what did I miss?

    Question about diagnosing a worn cam.

    A buddy of mine inherited a square body C10 with 454 & th400, 4.10 gears. (swapped in 14 bolt full floating rear, truck was used to tow) His uncle had rebuilt the engine 30 years ago, but we do not know any specs except the visible; holley vacuum secondary carb, no name single plane intake, stock HEI dist, generic long tube headers, aftermarket chrome engine tin, stock rocker arms, maybe aftermarket valve springs & cam (there are manley push rod guides, so there may be other aftermarket parts in it)

    It runs and idles OK, but has no power at all.

    60psi oil pressure on a mechanical gauge, no overheating issues, oil looks good, new plugs wires cap & rotor
    WOT is achieved when the gas pedal is pushed to the floor, the secondarys are not stuck shut
    Compression check, all cylinders about 150psi
    Vacuum at idle, 15

    I used a piston stop to determine “true zero” on #1. True zero was at 3-4 degrees advanced on the aftermarket chrome timing tab
    We set the timing to a true 16 degrees advanced, 35 degrees total, all in at 3000rpm

    We heard some lifter clatter so we pulled the valve covers to look for a worn lobe
    All valves moved about the same amount, no visible difference detected, BUT all rockers were loose when on the base circle.

    We put #2 on the base circle (intake open, intake closed and a little further) and adjusted to zero lash, spinning the pushrod while tightening until initial bind, then another 1/2 turn on intake and exhaust valve.
    Performed the same procedure on #4.
    Did a compression test again on 2 & 4, zero compression. Checked the rest of the nonadjusted loose cylinders, still 150psi. Loosened the rockers, compression came back but the rockers were loose

    At this point we figured we it was possible that the cam was worn, even on the base circle. Most likely this engine has aftermarket valve springs and has not had ZDDP/zinc additive it its oil since it was removed from all “off the shelf” oils.

    We removed the cam and lifters….and they look PERFECT! No detectable wear whatsoever. The cam bearings look beautiful as well.(engine is clean inside as well)
    What did I miss? It seems slightly hard to believe this cam is worn 100% even on all surfaces?
    I don’t want to stab a new cam in this thing if I have totally missed the diagnosis and there is some other problem.
    Last edited by andy30thz; April 29, 2018, 05:05 PM.

  • #2
    could you have seized lifters on those two holes?....as far as the no power issue.... did you test the distributor and timing curve for issues? I have been bitten by that one before....
    Patrick & Tammy
    - Long Haulin' 2008, 2009, 2010, 2011, 2012, 2014...Addicting isn't it...??

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    • #3
      Hmmmmm.... Seized lifters are a possibility, I couldn't depress the plunger in the lifter when out on the bench at all... I've never run into that before
      The truck sat for 6 year without running.

      Distributor seemed fine? I set it at 16 degrees advanced and the curve was 35 total at 3000 rpm.
      It is really lacking power. Can barely spin the tires in the dirt. I must be missing something!!
      Last edited by andy30thz; April 29, 2018, 06:16 PM.

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      • #4
        More info I should have added...
        The truck DID sit for an extended period of time.
        Fuel was drained, filter changed and carb rebuilt
        The power valve is new and the accelerator pump squirts a good stream.
        I have not done a fuel pressure test.(but I should)
        The plugs have a fair amount of carbon on them with minimal run time.

        In a no load situation/free rev, the engine will rev fairly well.
        Under load it will barely spin the tires in the dirt.
        It will drive around, but there is minimal acceleration if you transition from 1/16th throttle to full throttle.
        It doesn't fall on its face or breakup, its just slow.
        Exhaust seems open? I put my hand over the exhaust pipes and there is flow, nothing seems crushed? (But there could be internal muffler damage?)

        The lifters may be part of the issue. I tried to depress the plunger in a lifter and it feels seized with no movement. I didn't realize that could happen.
        If they were seized it could explain my loose rockers.
        But I'm not sure how that would impact performance? Or am I still chasing another problem?

        The cam is stamped;
        986
        13 46 88
        CR

        The lifters have no markings on them.

        This truck was an older guys, built to haul heavy and tow his cabin cruiser boat.
        I know the single plane is the wrong intake for this application, looking to address that while it is off.
        Last edited by andy30thz; April 29, 2018, 06:56 PM.

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        • #5
          solid lifters?
          My fabulous web page

          "If it don't go, chrome it!" --Stroker McGurk

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          • #6
            Seized, we had that happen with lifters after a couple hundred miles, so it happens, but when it happens, it also does not pump the oil thru the pushrods to the top end of the motor to lubricate the rocker balls so they may be ground down as well and create the slop too.

            Mistake I made was trying to just swap lifters because that ended up ruining the cam since they did not harden together. Hell, we figured the cam was not even broken in yet but it still rolled the lobes down.

            Get a good ball hone the size of the lifter lobes on the ones that were seized since they probably seized due to poor clearance getting them hot and locking them up when you swap the cam and lifters.

            But, with 150 psi compression, it sure seems like the valve train is moving to get the air in the cylinders.

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            • #7
              I don't believe they are solid lifters, this is a very simple build with mostly stock components for towing...but maybe?
              How can you tell a soild lifter from hydraulic visually?

              The rockers were really loose when on the base circle, like wobble them around in your hand loose.
              I just can't come up with a logical explanation why they were all so loose and all about the same amount.
              The reason it sat for so long was due to the previous owner having a stroke...so it is highly unlikely the rockers were backed off to save the valve springs while sitting.

              I may have caused part of the problem by trying to lash the valves AFTER the engine had just ran and they were pumped up with oil.
              My understanding is the hydraulic lifter is like a oneway check valve, not allowing the lifter plunger to depress when pumped up (and since it was run with no preload, they would be pumped up to the C-clip)
              That would hang the valves open if lashed in that condition. (is there a way to manually "bleed down" hydraulic lifters? or should it just happen on its own over time?)

              I am definitely a junior wrench and have a lot to learn!
              I have swapped a few cams and built a couple of motors...but this kind of diagnosis is new to me.

              My friend is totally on board to help and get his hands dirty, just he has less knowlege than me! This is a cool truck, with some family history/sentimental value and I just want to help him get it running well again.

              All the main componets seem to be there...I'm just missing something.

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              • #8
                From looking at pics on the web, hydraulic lifters have retainer clips for the plunger, solid do not.
                I have retainer clips, so I have hydraulic lifters.

                When I say seized lifters, I mean the plunger is seized inside the lifter. I've tried to compress the lifter plunger in the bench vice and it will not move.(I didn't REALLY crank on it, but I did give it prettty good force)

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                • #9
                  One of our farm trucks is a 454-4 speed.. Only used to haul hay. Clutch gets depressed and held down with a stick.. Runs real bad with bad lobes on the cam.. Worse under load.
                  If you have wasted lobes, you can hear the differences.
                  My 350 powered flatbed had a wasted cam when I bought it. Same symptoms. Runs real bad at speed, barely idles clean.
                  I have replaced cams in 350's and used used lifters, not in same bores. Not sure how good of an idea that is.. Replaced lifters later tho for peace of mind

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                  • #10
                    there are solid lifters with a removable cup, held in by a clip.

                    My fabulous web page

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                    • #11
                      If you want to see what kind of lifter it is, take one out, and take it apart.
                      My fabulous web page

                      "If it don't go, chrome it!" --Stroker McGurk

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                      • #12
                        Hydraulic lifters will bleed down, but they are tough to do by hand. Valve spring pressure should normally be enough to do it. I just took some apart and my sizable girth could barely compress the cup to get the retaining clip out. Then the plunger section had a strong suction and required some oomph to pull it out. I drained the oil and then stuck them back in to check preload.

                        I'd say adjust all the rockers as they should be. They will probably hold the valves open a few revolutions until they bleed off some oil. Or pull them and drain them. Sounds like they have been being run with no lash so they are likely completely full of oil.
                        Life is short. Be a do'er and not a shoulda done'er.
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                        • #13
                          Originally posted by BBR View Post
                          I'd say adjust all the rockers as they should be. They will probably hold the valves open a few revolutions until they bleed off some oil. Or pull them and drain them. Sounds like they have been being run with no lash so they are likely completely full of oil.
                          Thanks guys!! This is definitely info we need!
                          I agree, with it being run with zero lash, they are completely pumped up, so when I set the lash like you would with empty lifters...I inadvertently added approximately 0.030's lift and hung the valves open, causing no compression... I assume with them pumped up 1/16-1/8's preload would probably be more appropriate than the 1/2 turn we gave it before.

                          I guess what threw me off was that all the rockers were completely loose and the engine LOOKED untouched? I know things can loosen up over time....but every single one exactly the same...and I've never had a rocker back off THAT much from what looks like a basically stock rebuild?
                          The only thing we can come up with is the previous owner backed off all the rockers for storage reasons and he knew how many turns it would take to put it back.
                          Everything else looks perfect! I think I ended up just chasing my tail...looking for answers to the wrong questions.

                          Tell me if I'm wrong, but having the rockers loose like that should effectively make the cam tiny and allow the engine to run...but have no power?
                          Unfortunately with the rockers that loose the oil wasn't getting through the push rods to the rockers and valves... I'm going to need to look a lot closer to see if there is any wear or damage. Fortunately it wasn't run too long like that.

                          We are going to throw it all back together(we marked the lifters with lobe position) with just a new timing chain(the old one had slack) and Performer RPM intake(nonairgap)
                          I'll let you guys know the outcome.

                          Unfortunately we can't find any info on this cam...there are only numbers stamped on the back by the cam gear and nothing that we can find on the front.
                          I would have liked to add a generic 218/228 cam while we were here....but I rather make sure everything is RIGHT before we make other changes and confuse the issue.
                          Last edited by andy30thz; May 1, 2018, 06:15 AM.

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                          • #14
                            when you adjust the rockers do NOT try to do it by twisting the pushrods to see when there is zero lash. Instead, move the rocker in the direction it travels, you will feel it definitely have free play when it's too loose, then as you get close to, then reach zero, it will stop moving. Stop tightening the nut at this point, it is at zero lash.

                            My fabulous web page

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                            • #15
                              Makes sense to me! At this point stay with zero lash instead of any additional preload?
                              Last edited by andy30thz; May 1, 2018, 09:42 AM.

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