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pushrod length

Discussion in 'Intermediate CJ-5/6/7/8' started by ronar, Feb 15, 2011.

  1. Feb 15, 2011
    ronar

    ronar New Member

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    Mar 13, 2010
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    I have a tappet noise in a 77 304. I have never been inside an AMC v8 so it is new to me. I pulled the left valve cover and 2 of the rocker arms are loose on the valves/pushrods. Both are intake valves. My guess is a worn
    camshaft. Unless of course the pushrods are of different lengths. I doubt that even tho I have seen that in some engine in the past. I didn't do a camshaft lobe measurement but those two valves don't appear to be traveling as much as the others. I have been a mechanic for over 40 years and have seen a worn camshaft lobe only once before, on a ford 302. Is this a common thing on the 304? I was surprised to find the top of the head very clean and all the rocker arms oiling well. Anyway the question is....are the push rods all the same length? My service book didn't say, it just kept repeating that the valve train components need to be reassembled in the order they were removed.
     
  2. Feb 15, 2011
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Without oil pressure, there will be slack on some of the rocker arms. Rotate the engine and see if the slack moves to other rockers.

    That said, the AMC V8s have been known to wipe out cams. But I would not assume that on just this data. Also, a lifter tick is annoying but not critical.

    Yes, they are all the same length. It's just good practice to keep the valve train components in their original locations. I don't think anything bad will happen by mixing up the components unless you mix up the location of the lifters that have worn in to the cam, however.
     
  3. Feb 15, 2011
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    pivot and or rocker arm wear can cause the same condition.
     
  4. Feb 16, 2011
    Pack Rat

    Pack Rat Old Timer

    I live in a...
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    I wouldn't rule out a worn lobe but more inclined towards a worn pivot/rocker arm or a weak lifter. Rocker arm is easiest to check. You're lucky if you only saw one bad cam, couldn't begin to tell you how many 305 Chevy camshafts I replaced. Probably going to have nightmares about that now. Maybe this will help me sleep better bunny with a pancake
     
    Last edited: Feb 16, 2011
  5. Feb 16, 2011
    Corveeper

    Corveeper Member

    Chanute, Kansas
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    Oh man, tell me about it. That’s exactly why I went roller top end and won’t ever go back, a little expensive to set up initially but the end result is well worth it.
     
  6. Feb 16, 2011
    Corveeper

    Corveeper Member

    Chanute, Kansas
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    I’m with Tim here though, I wouldn’t necessarily suspect a flat cam lobe. Almost every instance I’ve seen or heard of cam lobes going flat has been on new motors or new cam install. Its unusual for an engine that’s been out running around the street for a while to just suddenly knock a cam lobe flat.
     
  7. Feb 16, 2011
    ronar

    ronar New Member

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    Thanks for all the replies, I still have not measured the cam lobe heigth but because I had a little time and some extra valve train parts........I measured all the push rods on the side I had the cover off of already. I removed both the rocker arm assemblies that were noisey.......I measured the rocker arm pivot (stationary part the bolt goes through) and then carefully ground about 50 thousands off the surface that contacts the cyl head. I reassembled and the noise was gone.
    Now, I know that is not the correct fix for this problem, I know I will have to replace the camshaft at a later date, but......it gained me a short reprieve til I have time to fix it right.
    Because I also measured the valve travel before and after this "fix" I know I gained a little more valve motion due to the slack being reduced and I know also that the valve is NOT being held open because I did a compression check. An open valve would show up there. Sometimes you can learn something just by playing around with these things.
    Ron
     
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