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Discussion Starter #1 (Edited)
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.
 

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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.
 

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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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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
 

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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
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
 

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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:)devil
 

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Discussion Starter #9
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?
 

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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?
Let me get this right, more rpm and the noise does not speed up?????????
 

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Discussion Starter #13
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 :)coffee
 

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Discussion Starter #14
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.) :confused:
 

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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.) :confused:
Okay skipper, Time to think out your'e problem. Lets think about what you said, goes away at idle meaning no noise at almost zero load. Disconnect plug wire and then reattach and returns. Unburn't feul in the cyclinder being fired. Oil pressure good. WRIST PIN. Fire the engine and put it in gear and put a load to it and listen then. Push rods tick all the time. rod bearings knock all the time. The only sound that I ever heard out of a motor that came and went was rod/piston related. Load test will verify. And fyi no shop wants to eat a bad press job or to dry on fire-up in the pin boss. IMO Mark
 

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I is starting to sound like a piston slapper.
Hey hallett, Very well could be but I have seen to many wrist pins create the same situation. Best part is the oil pressure is good so it is not a serious fix. I have also seen daily drivers live with this for lots of miles and even go away in a few cases. Alot of boats have little ticks and knocks that because of an open exhaust or whatever go unnoticed for a long time. When I build a motor I will actually use a SMALL amount of lithium grease on the pins cause you never know how long it will be before the motor gets lit-up and oil runs off as does alot of assembly lube. Remember you are playing with dissimular metals and the only lube a wrist pin gets is splash and oil ring run off. IMO Mark
 

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Discussion Starter #19
So it sounds like a wrist pin? Kind of new to this and want to get it fixed, what ever it is. I gave the builder a little over $3000.00 for the rebuild. New pistons, rods, cam (hopefully lifters), intake, carb. I probably should have done it myself and saved $$, but was afraid I would screw it up. Evidently I would not be the only one to do this :mad: So now it is me fixing with yall's help and from what I understand I need to put a load on the engine to see if it goes away, gets louder, or? I hope its not anything serious:(
 

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Discussion Starter #20
louder at idle then when you increase the throttle seems to diminish, but still there, not as loud though.
 
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