engine noise (knocking)

[Scott Danforth]

start by removing the drive. this will let you know if the issue is the motor or the drive.

 

[Bondo]

start by removing the drive. this will let you know if the issue is the motor or the drive.

Ayuh,.... Ditto,...... Any metal or debris in the oil of the drive, or motor,..??

 

[betayv]

I pulled the outdrive already and still the same knock, I remove valve cover gaskets and clean oil, not metal.

 

[Bondo]

I pulled the outdrive already and still the same knock, I remove valve cover gaskets and clean oil, not metal.

Ayuh,... Did ya turn it over, or run it,..?? Is Everythin' Movin',..??

Do a compression test,....

 

[funk6294]

Ditto on the compression check. You likely will not find metallic debris in the oil in the heads, that would usually wind up in the pan. Also if you have the valve cover off take a look at all of the valves and see if one sits noticabley higher than all of the rest. You may have to rotate the motor a time or two for them to each reach closed position. I had one do the same thing and it was due to a dropped valve seat.

 

[betayv]

yes everything turn and the engine starts just with the knocking, did a compression test 150 all the cilinders

 

[alldodge]

Sounds like you spun a bearing

 

[Mischief Managed]

Take the belts off the engine and start it again. A failed bearing in belt-driven accessory (especially the circulation water pump) can cause a sound that is remarkably like a rod knock. If that does not help, pull one plug wire at a time and run the engine to see if the noise goes away. If it goes away with one plug not firing, the noise is likely caused by a rod bearing on that cylinder.

 

[JustJason]

A mechanics stethoscope is going to be your best friend here.

 

[betayv]

hello guys little update 1987 searay 5.7 engine, engine was running on muffs on idle, good temp, good oil pressure, suddenly start making a noise knocking, I shut down the engine, restart and same knocking, I remove the outdrive and start the engine same knocking, did a compression test prior to the noise all the cylinders 150, well time to pull engine out and inspect, my friend who is a master tech is help out, we remove oil pan, and not metal or any particles around clean oil, remove and inspect main bearing and connecting rod bearings and not signs of wear or damage, any advice thanks.

 

[rickryder]

Pop the pistons and check wrist pins

 

[NHGuy]

Did the distributor get loose and turn to a high advance value? If your engine sounds like marbles in a metal can it could be spark knock.

 

[betayv]

the distributor never got loose but I was reading that a bad mixture carburetor can cause spark knock, how the noise will go away, how can I fix this.

 

[Bondo]

the distributor never got loose but I was reading that a bad mixture carburetor can cause spark knock, how the noise will go away, how can I fix this.

Ayuh,...... Detonation happens at hi-loads, 'n usually higher rpms,...

If yer motor is knockin' runnin' in the hull, without the drive,.....

It Ain't detonation,....

It's a mechanically problem, like a bad motor bearin',....

well time to pull engine out and inspect, my friend who is a master tech is help out, we remove oil pan, and not metal or any particles around clean oil, remove and inspect main bearing and connecting rod bearings and not signs of wear or damage,

The wrist pins are next,...

 

[betayv]

ok guys little update here founf the issue, like I said bearing are good, take out the heads to find out cylinder number 7 has some metal big parts on top of it, I don't know hoe this got there the only explanation is thru the intake and most be something from the carburetor.

 

[Fun Times]

Could you try posting a photo of the metal and damage if any? Maybe someone will recognize something.

Good luck.

 

[hottoddie]

Same thing happened to one of my 454's 2 years ago. Was a 5/16" carbon steel lock washer like the ones on the carburetor mounting studs. Did a valve job while the heads were off and all was good after. No idea how the lock washer got there but I blamed myself.

 

[alldodge]

ok guys little update here founf the issue, like I said bearing are good, take out the heads to find out cylinder number 7 has some metal big parts on top of it, I don't know hoe this got there the only explanation is thru the intake and most be something from the carburetor.

Take a pic of what you see as FT mentioned. How do you know the bearings are OK?

 

[betayv]

not sign of wear or damage on the bearings, not metal particles in the oil, is down now so I will put new bearings on it, drop the head in the machine shop today, already bought the damaged piston, and piston ring set, head set, new oil pump, new fuel pump, I guess is time to do a major refresh on the engine, and by the way I'm getting a new edelbrock carburetor.

 

[alldodge]

Trying to figure out what was knocking, found anything loose?