Problems with valve lash on rebuilt 318 poly

Engine, Transmission & Driveline

  1. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    motor was out and rebuilt. Reinstalled. Everything working. Sounded like it needed the valves adjusted. Rattling a lot. Pulled a valve cover. Went to adjust them, but I can’t.

    Most of the pushrods are loose and I have no room on the adjusting screw to tighten them up.

    The problem had been getting progressively worse and the motor is just not making a lot of power.

    I’ve pulled the intake. Everything looks new and good. Cam doesn’t look worn down. Tappets all look clean and new.

    I’m not a motor guy and the guy that built it is an engine genius but was not that familiar with poly’s. Did we miss something?

    I have to think this is some kind of simple problem. He is coming over to look at it. He suspects the cam lobes are softer than the tappets and may have just ground them down during a poor break-in procedure by me. The motor has about 400 miles on it and one oil change.

    There is lots of wisdom on this board and I am hoping to tap into some it!
     
  2. Wollfen

    Wollfen Old Man with a Hat

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    I am thinking it is going to be worn down cam and tappets, sorry to say but that would require replacing the camshaft from what you have described. Can you supply pics off the cam as much as can be seen and also pics of the rocker gear too? That will help us.
     
  3. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    What year poly is this? 400 miles would be pretty fast for a whole cam to go flat, something would have to be very wrong. The 318 polys all ran mechanical lifters and the camshaft would be hardened to accommodate those lifters, it would be very unlikely that a hardened cam would go that fast. Check your filter for many specs of shiny metal, a good indicator of a failing cam. Was the engine noise there at the beginning or did it get worse as more miles were put on it? Check the rocker shafts, are they tight against the head? Sometimes when a head and block are planed, the head bolts are then too long to where they are bottoming out before they are tight against the rocker shaft. If that is the case, you should see movement of the rocker shaft with the engine running. If that is the case, you probably also have a coolant leak into the cylinders or crank case. Did you inspect the rocker shafts and rockers from you engine? If they are excessively worn with big groves cut in the bottom of the rocker shafts, that could be why you are out of adjustment. The other possibility, if the push rods were replaced, they might be too short. Check these things and report back.

    Dave

    Dave
     
    Last edited: Jun 13, 2019
  4. mr. fix it

    mr. fix it Old Man with a Hat

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    This seems strange
    Were the valves changed or ground down when rebuilding the heads?
     
  5. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    Here are the cam lobes for cylinder 3&4 through a full rotation.

    Noise was always there, but lately worse. Hence why I intake to inspect when I couldn’t adjust. Is it possible to order push rods that are too short?


    The builder did say he had them set right when he built it. I may have even asked if he could have had the wrong parts. TI he tappets look new as do the pushrods. Not visible wear patterns.

    I did pull the spark plugs and found the spark plug in #8 crushed. I put another one in and cranked by hand and it was not struck. I’m not sure if I put the. In or the builder did, but I would not have put in a bent one.

    BC9CC8DD-2902-47F0-8AB9-B91FF1CDE710.jpeg 40F62A79-09C6-4FC7-ABE0-7A09F50FF647.jpeg 65E4B5A9-619F-4CC8-AB77-D24A6C00A45C.jpeg 180509CA-D739-4581-8E55-190CC4915196.jpeg 67F96F1D-AA4C-461F-9C79-FB2F931DD34D.jpeg ECACE907-6DF5-4CF0-BDD3-B5A38B850A69.jpeg
    image.jpg image.jpg
     
  6. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Cam is not flat and appears to be breaking in normally. Plug looks like somebody dropped it as it does not show damage from foreign object contact. Push rods are new and most likely the wrong ones. Start there. If you have one of the old ones, check the length against the new ones. Push rods look way short as they should be more or less centered on the lifter.

    Dave
     
  7. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Also, clean out the paint chips prior to reassembly.

    Dave
     
  8. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    I'm not familiar with the early 318, so I'm just tossing something out there...

    If you can't adjust the rockers enough, and everything looks OK, I would take a look at push rod length. You didn't say if you have hydraulic lifters now and if you reused the original push rods. You may have to have some custom length push rods made.
     
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  9. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    I assume you pulled the two missing push rods.

    Dave
     
  10. mr. fix it

    mr. fix it Old Man with a Hat

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    I was just about to post this as well.
    Are these the original pushrods?
    If not then hopefully you have access to the original ones for comparison purposes.
     
  11. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    Yeah....housekeeping is in order here! I spilled a little antifreeze too.
     
  12. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    Yes. Took them to the builder. He confirmed they still look new and sent me back to get pics of the cam pending him coming over here.

    The valves are all new. New springs, pushrods, tappets. I doubt the originals are still around.

    I am beginning to like the idea of just replacing pushrods.
     
  13. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    Somebody on this site is bound to have a junk 318 poly laying around that you could have them measure one of the push rods for comparison. You are off about 3/16"-1/4" to be out of adjustment with yours on the short side. Most of the time, if valves have been ground and the head and block have been planed, the push rods will be too long if anything.

    Dave
     
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  14. mr. fix it

    mr. fix it Old Man with a Hat

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    I have a stock 1966 poly engine that I can check tomorrow
    If I recall correctly, the intake & exhaust rods are a different length but can confirm that was well
     
  15. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    That might be it. Poorly documented in the factory manual and some fit
     
  16. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    The mechanical tappets are different than newer style mechanical tappets. The look much different.
     
  17. mr. fix it

    mr. fix it Old Man with a Hat

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    That may be where the problem lies.
    Working on getting those measurements for Eddie
     
  18. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    Thanks man.
     
  19. mr. fix it

    mr. fix it Old Man with a Hat

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    The length of the pushrod’s is equal for intake and exhaust
    It is 8-17/32” for the stock length
     
  20. Fast Eddie B

    Fast Eddie B Active Member FCBO Gold Member

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    Thanks much. That is from an original block? Just confirming.

    I am just leaving town for the week, but when I get back i’ll measure the rods. the builder is coming over to inspect. He is convinced he had it set right on the bench. But when I tighten the adjusters all the way they are coming up around an 1/8” too short.

    It was somewhat loud from the start. Got worse. We’ll see. Old rods are gone BTW.