454 Knocking Sound
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454 Knocking Sound

  1. #1
    Senior Member Quit Yer Bitchin's Avatar
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    Default 454 Knocking Sound

    Took the boat to the launch yesterday to set timing and for first run after engine assembly. Right from the get go I can hear a knocking sound coming from the passenger side bank. Didn't sound like a rod knock, the frequency seemed too slow. I laid my head down on the valve cover and verrified the noise was definitely originating from the passenger side. Driver side bank was nice and quiet. After setting timing and idle we took it for a test spin. I can definitely feel a miss or surge upon acceleration. Oil pressure is around 25 psi at idle and at 40psi at higher rpms. Back to the dock, still knocking. Shut it off, check oil, looks fine. Tighten exhaust manifold bolts, fire it back up, still knocking. Then the knocking starts coming and going. It would knock continuously and then stop for 15 seconds and then start knocking again. WTF!?

    To give you the background story, I acquired a gen 5 454 with 40 hrs of run time. The boat was stored in a building over winter and the building caught fire. The plan was to put it in my boat until I discovered the block was cracked due to improper winterization. I wound up buying a brand new GM performance 454 block from summit racing and swapping over all internals (crank, pistons, rods, cam, lifters, push rods, rockers, and timing set). I used new bearings on crank both main and rod in addition to new cam bearings. I used plastigauge to check oil clearances on all journals which were a little on the tight side. I was told by the techs at Mahle that this was normal with the type of bearings I was using. I checked end gap and side clearance for each ring which all fell within spec. I should mention that the new block is a gen 6 but from my understanding, not much difference exists between the gen 5 and gen 6 blocks. I should also mention the cam is a hydraulic flat tappet. The cam and lifters were not replaced.

    Got home from the launch and pulled the passenger side valve cover off. I was hoping to find a collapsed lifter. All rocker arms had the normal amount of play. These are the non-adjustable type. All the lifters were pumped up and would not compress when applying pressure.

    Today I pulled the distributor and put the oil priming tool in. The tool I use was made from an old distributor with the drive shaved down. I was turning it with a power drill. Oil pressure was around 40 psi. It seemed like the driver side bank was getting more volume than the passenger side. All rockers on the driver side had a nice steady drip. The first 3 rockers on the passenger side were getting oil but did not have the same steady drip as all the others.

    I read something about the oil galleies that feed the lifters having threaded plugs at the front of the block where they terminate next to the cam bore. Some were saying to drill holes in the plugs to allow trapped air to escape. Not having the holes can cause lifter noise on start up. I don't remember if the plugs that I removed from the old block had holes in them. I know I installed some new plugs in some locations but do not remember where and do not remember if the ones that came out of the old block went back in the same places.

    I don't know where to go from here. Can a lifter intermittently make noise? Can a liftet pump up and be stiff but fail under the force applied by the cam lobe?

    Any help will be appreciated.

    Thsnks
    Last edited by Quit Yer Bitchin; 06-11-2017 at 04:14 PM.

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  3. #2
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    Default

    make sure you have the right size valve locks.

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    Senior Member Johnny2bad's Avatar
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    Default

    I dynoed a fresh 440 Mopar and spent 2 hours tracking down a knock in the timing gear/ fuel pump area up near the front of the engine.

    Turned out to be a vacuum leak at the base of the carb/gasket.

    I would have bet against that possibility until I actually saw it.

    Good luck.
    Johnny
    Posted from my Etch A Sketch

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  6. #4
    Senior Member Quit Yer Bitchin's Avatar
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    I never disassembled the heads so I don't think it's the valve keepers.

    Johnny2bad, how was the vacuum leak causing a knock? Right now I have the breathers on my valve covers running through hoses to an oil separator then to a large vacuum port on the back of the intake manifold. Essentially the crank case is in a vacuum. I wonder if this is causing a problem or disrupting oil flow some how.

  7. #5
    formerly 67lefty 1967lefty's Avatar
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    Default Mechanical fuel pump?

    If you are useing a mechanical fuel pump you might want to check it and the fuel pump rod

  8. #6
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    No I'm using an electric fuel pump. I took the boat to the launch again to try and pin point this knock and its gone. I wonder if I had a bad lifter that pumped up eventually. Could have had a stuck check valve that freed up.

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    gotta love it when they fix there self..

  10. #8
    Senior Member Johnny2bad's Avatar
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    Quote Originally Posted by Quit Yer Bitchin View Post
    I never disassembled the heads so I don't think it's the valve keepers.

    Johnny2bad, how was the vacuum leak causing a knock? Right now I have the breathers on my valve covers running through hoses to an oil separator then to a large vacuum port on the back of the intake manifold. Essentially the crank case is in a vacuum. I wonder if this is causing a problem or disrupting oil flow some how.
    I have no idea, the shop owner said he has come across this before with vacuum leaks making noises you would never imagine.

    We had the front off that engine twice.....he too thought it was a mechanical problem at first......then his kid came in and suggested a leak.

    If I had not have seen the pinched base gasket and actually heard the noise it created, I would not have believed it....ever.
    Johnny
    Posted from my Etch A Sketch

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    Senior Member wolfie's Avatar
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    Quote Originally Posted by Dchallenger View Post
    gotta love it when they fix there self..
    Those worry me more for a while since you never knew what caused it in the first place. Although I always like the price of that fix!!!

  12. #10
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    Quote Originally Posted by wolfie View Post
    Those worry me more for a while since you never knew what caused it in the first place. Although I always like the price of that fix!!!


  13. #11
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    Could have been a Valve trying to stick in the guide . 40 psi seems low for a fresh bearing job in a BBC , If your lifters are used , they very well could be clacking alittle.

  14. #12
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    I had a brand new litter on my Harley after a cam upgrade that made a knocking sound. Come to find out after a few hours of trouble shooting , the litter was not bleeding down due to some crap blocking the weep hole. Took the litter apart, cleaned it out and that fixed the knocking issue.

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