Help! Small block 360 has a knocking sound

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CheeseRules01!

CheeseRules01!

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A little while ago, my Dart's 360 developed a pretty noisy knocking sound. Initially it sounded kinda like a dead cylinder, checked all the plug wires and sure enough, one of my plug wires was leaning against the header and it burned straight through. I replaced all plug wires, spark plugs, it has a new coil, and still has a knocking sound. I pulled the valve covers off and watched it run, all of the valves were opening and closing just fine, nothing looked damaged. I'm starting to think it has a rod knock, but the weird thing is, you can kinda hear the knock in the exhaust, so I'm not really sure anymore. Also did a compression test, all 8 cylinders are very healthy at about 200 PSI for every cylinder (Varies a little between cylinders of course). I am stumped, anyone got some ideas? Thanks.

 
CheeseRules01! said:
A little while ago, my Dart's 360 developed a pretty noisy knocking sound. Initially it sounded kinda like a dead cylinder, checked all the plug wires and sure enough, one of my plug wires was leaning against the header and it burned straight through. I replaced all plug wires, spark plugs, it has a new coil, and still has a knocking sound. I pulled the valve covers off and watched it run, all of the valves were opening and closing just fine, nothing looked damaged. I'm starting to think it has a rod knock, but the weird thing is, you can kinda hear the knock in the exhaust, so I'm not really sure anymore. Also did a compression test, all 8 cylinders are very healthy at about 200 PSI for every cylinder (Varies a little between cylinders of course). I am stumped, anyone got some ideas? Thanks.

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That’s not happy engine. Really hard to make out the sound though. I had a similar issue that turned out to be a leaking gasket. Good luck on your search, you’re in good hands here.

Jake
 
First of all, when I saw your username I assumed you were from Wisconsin :D ! 2nd of all, the video is hard to hear, but I do not think it's a rod. Sounds like valve train noise in the video, but again it's hard to hear.
 
318willrun said:
First of all, when I saw your username I assumed you were from Wisconsin :D ! 2nd of all, the video is hard to hear, but I do not think it's a rod. Sounds like valve train noise in the video, but again it's hard to hear.
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lol, when I made my username i must have been loopy or something. Anyways I agree with you, I was thinking that it sounded like valve train noise. Sorry about the quality of the video, its all I got. The sound itself seems to be coming from the rear center of the engine. You can hear the knock on either side of the motor.
 
CheeseRules01! said:
lol, when I made my username i must have been loopy or something. Anyways I agree with you, I was thinking that it sounded like valve train noise. Sorry about the quality of the video, its all I got. The sound itself seems to be coming from the rear center of the engine. You can hear the knock on either side of the motor.
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Does it seem to be more on top of the engine? or more down deep in the engine??
 
Its kinda hard to tell because the knock is so loud, but it seems more towards the top of the engine.
 
CheeseRules01! said:
Its kinda hard to tell because the knock is so loud, but it seems more towards the top of the engine.
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Back of the engine and top..... I suspect a torque converter bolt backed out a hair and is hitting. Drive it up on ramps, get your wrench and check
 
rustycowll69 said:
200 psi seems kinda high. how modified is this engine?
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the funny thing is I don't know, I didn't build this engine. Whoever built it put a competition cam of some sort in it, and Keith Black 9:1 pistons, that's all I know. Besides, I think the reason for the super high compression is carbon build up, this car was my daily driver for quite a while.
 
That’s for sure something on the converter or flex plate. not a rod knock
 
hydraulic or solid lifter? It sounds like a lot of valve train noise. Possibly too much lash. Are you sure it is oiling properly, too?
 
Try replacing your mechanical fuel pump.

Had one of those making a knock on a small block. The knock went though the whole engine making it sound like a rod or exhaust manifold leak, but not.

The arm going into the fuel pump was loose where it met the diaphragm plunger. The new pump was not loose there, and the noise went away.

Found it by putting a long 3/8 extension at my ear with the other end on the fuel pump, that was it.
 
rustycowll69 said:
hydraulic or solid lifter? It sounds like a lot of valve train noise. Possibly too much lash. Are you sure it is oiling properly, too?
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its got hydraulic lifters, i wiggled all of the rocker arms around and nothing was loose or making noise. I watched it run without the valve covers on and everything was getting oiled just fine.
 
George Jets said:
Try replacing your mechanical fuel pump.

Had one of those making a knock on a small block. The knock went though the whole engine making it sound like a rod or exhaust manifold leak, but not.

The arm going into the fuel pump was loose where it met the diaphragm plunger. The new pump was not loose there, and the noise went away.

Found it by putting a long 3/8 extension at my ear with the other end on the fuel pump, that was it.
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interesting might have to try it, but the sound is definitely distinctly coming from the rear of the motor.
 
Yeah those header tubes exaggerate the noise too, so it's hard to pinpoint the source.

Some guys have those stethoscopes to help them find sources of odd noises.
 
CheeseRules01! said:
interesting might have to try it, but the sound is definitely distinctly coming from the rear of the motor.
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Yeah, crazy that fuel pump can send that knock right down the camshaft sounding like it is coming from the back of the engine.

The fuel pump knock I found, you could hear it over by the passenger side interior heater box, while sitting in the driver's seat with the engine idling. Very annoying and confusing trying to figure out where it was coming from.

Keep looking, you will find it.
 
Had a barracuda with a 340,I was driving down the road one day and it started making a knocking noise. It ended up being the torque convert was cracked going into the pump.
 
I had a similar issues. Turned out the oil pump drive shaft bushing froze to the shaft and wore down allowing the drive shaft to go loopy. Made a mess of brass shavings thru out the engine. Had to completely tear down to clean the engine. Also cam bearing replacement as it destroyed the back bearings.
 
This is what rodknock sounds like
(It flutters after you let off, yours doesnt do that, so time to pull your valve covers)

 
diymirage said:
This is what rodknock sounds like
(It flutters after you let off, yours doesnt do that, so time to pull your valve covers)

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ok, what do you suggest I look for? I have pulled the valve covers and watched it run, and everything is oiled and working just fine. No bent push rods, nothing was loose, all valves are opening and closing just fine.
 
How fresh is the engine? Is it still close to its break in? It sounds to me like diesel knock. That's indicative of high cylinder pressure. Piston slap. Engines with really high cylinder pressure like that one has, will usually exhibit a diesel like knock mostly when cold, but it gets a little quieter as the engine warms. Usually, it's most audible JUST above idle, with the throttle barely cracked. If that's what it turns out to be, ride on brother. It's normal.
 
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