Rod Knock or?
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Rod Knock or?

  1. #1

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    Default Rod Knock or?

    This is not on my jet boat, but on my 1972 Plymouth Satellite 400cid, 4 barrel. I had the engine recently rebuilt and have developed what sounds like a knock on the #5 cylinder. I read that you can determine if it is a rod knock by pulling the plug wire and eliminating the detination allowing for the piston to stop knocking assuming that it is a bad rod bearing. When I do this I notice that it does quiet down but does not go completely away when the plug wire is disconnected on #5. When I hook it back up it comes back. With all plug wires conected It is louder at low RPM's and seems to diminish when I raise the idle. I read that a rod knock gets louder at higher rpm's. confused and ???? further I do not know if he primed the oil pump I did not since the timing chain was on already when I got the motor.
    Last edited by dgie; 07-16-2008 at 11:45 AM.

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  3. #2
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    "It is louder at low RPM's and seems to diminish when I raise the idle."

    Usually that is a piston knock and not a rod.

  4. #3
    cfm
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    Stop running it. Take off and cut open oil filter. Check for debris.

    Why do the jackass engine builders get off scott free and the good guys end up with their messes - mental/physical/time/$$$$ ?

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    Cantard 71hallett's Avatar
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    If it goes away when you rev it up are you sure it isnt a flex plate or something? I would pull the belts of first, could even be something like the alt or water pump. I know a guy that pulled his motor because the spring in the starter was broke. lol
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Quote Originally Posted by 71hallett View Post
    If it goes away when you rev it up are you sure it isnt a flex plate or something? I would pull the belts of first, could even be something like the alt or water pump. I know a guy that pulled his motor because the spring in the starter was broke. lol
    Sounds alot like wrist pin or piston slap to me. How is the oil pressure, and what clearance on the piston to wall and what composite pistons are ine the motor. Cast, forged or hypertheraputic. Cant spell the hyperutechtik word. Lots of options here and oil pressure will tell the tale. IMOOOOOOOOOOOOOO M

  8. #6
    Cantard 71hallett's Avatar
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    You got it Mark. Lots of options.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Quote Originally Posted by 71hallett View Post
    You got it Mark. Lots of options.
    Oil pressure will tell the answer. If normal, probably piston or as you said external noise. If oil pressure is in the outer limits or below ground level, bottom end, If normal than ring,piston or over clearance problem. or exterior noise resinating to scary areas. My O2 M

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    Sometimes a rod will have a squwak noise instead of a stright knock! WT

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    Oil pressure looks good, at idle it is around 25 psi and when I give it throttle its up to 50 psi. I thinks thats normal ??? I did take it to the builder yesterday and he said that it is not piston slap since it does not get louder or faster when you give it throttle. He suspects it a bad push rod and is going to order it for me. Does this sound right?

  12. #10
    Senior Member ol guy's Avatar
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    Quote Originally Posted by dgie View Post
    Oil pressure looks good, at idle it is around 25 psi and when I give it throttle its up to 50 psi. I thinks thats normal ??? I did take it to the builder yesterday and he said that it is not piston slap since it does not get louder or faster when you give it throttle. He suspects it a bad push rod and is going to order it for me. Does this sound right?
    Let me get this right, more rpm and the noise does not speed up?????????

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    Cantard 71hallett's Avatar
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    Quote Originally Posted by ol guy View Post
    Let me get this right, more rpm and the noise does not speed up?????????
    It,s one of those special pushrods. Pushrod would be more of a tick than a knock.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Cantard 71hallett's Avatar
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    Loose flywheel? Converter bolts?
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Quote Originally Posted by ol guy View Post
    Let me get this right, more rpm and the noise does not speed up?????????
    It sounds like the noise speeds up to me, but not as loud when the rpm's are raised it may be a tick, knock, something like that. I just hope he gets one of those magical push rods so what ever the hell it is goes away

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    Quote Originally Posted by 71hallett View Post
    Loose flywheel? Converter bolts?
    At idle the noise diminishes when I pull the #5 plug wire from the distributor then comes back when I reattach it. The flywheel does not know this, neither does his little buddies (the bolts on the converter.)

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