Big cam

[charles walton]

I have a 79 IH 2475 with a 350 big cam and it makes a knocking sound on crank up that sounds like it is coming from the harmonic balancer. I don’t know much about it, it quits after a couple minutes idling and runs great but it sounds bad on crankup. Can someone tell me what if anything I should check out first?

 

[Truck Shop]

A harmonic balancer that old is more than likely frozen internally. What's oil pressure cold?
Loosen belts and check side to side and end play on accessory drive first. End play should
be no more than .012.

 

[charles walton]

A harmonic balancer that old is more than likely frozen internally. What's oil pressure cold?
Loosen belts and check side to side and end play on accessory drive first. End play should
be no more than .012.

This engine is a Cummins factory reman that has low mileage. What is on the inside of the balancer? I’ll try to check that measurement and also see if it makes the noise with the alternator belts off, I will check that oil pressure but it seems like it was good because I haven’t been concerned and I usually watch that when I first get a different truck.

 

[kshansen]

If it would make you feel better I might try removing the damper and start the engine for a few seconds just to prove it's not the damper.

 

[RocketScott]

It has a weight suspended in a viscous fluid. Mineral oil of some sort I think

If the fluid leaks out, dries up, or it gets a dent that prevents the weight from moving it stops working

Did the reman come with the balancer or did they reuse the old one?

 

[Truck Shop]

I'm out the non mechanic einstein is in.

 

[kshansen]

I'm out the non mechanic einstein is in.

sorry if I was out of line with my thoughts!

 

[Truck Shop]

sorry if I was out of line with my thoughts!

All is fine.

 

[RocketScott]

sorry if I was out of line with my thoughts!

Think he was talking about me

 

[charles walton]

It has a weight suspended in a viscous fluid. Mineral oil of some sort I think

If the fluid leaks out, dries up, or it gets a dent that prevents the weight from moving it stops working

Did the reman come with the balancer or did they reuse the old one?

Not sure about whether it was replaced or not but the sound is very much like what you would think the weight in oil might sound like if it’s hitting the walls inside the balancer because the oil is pooled up or low. I didn’t know what was inside of it.

 

[Truck Shop]

First off there is not enough clearance inside damper cause a knock, second just because it's
a Cummins rebuild doesn't mean the damper was changed, third the easy way to tell if the damper
is working is will be warm after 30 minutes of run time if cold it's froze. Being a 350 it should have
a 12" damper-400's & N14 use 13.5" damper.