What does a rod knock sound like. i rebuilt my motor earlier this year. good oil pressure and no smoke. if possible i would like a sound file of a rod or main bearing knock. motor is 89 460 fi. i appreciate any and all feedback

Daniel Pennington
69 IH scout 800A
1989 F350 CrewCab Dually 460 C6
1981 F350 4X4 Flatbed 460 C6

 

The best way to tell if you have a rod knock is to get a long screwdriver or something like that, and put it up against the engine block when it's running, and put your ear on the other end. You will be able to tell right away if you have a rod knocking.
A rod knock sounds like the tick-tock of a clock. It will happen at all RPM's and get louder at higher speeds.

 

Well, to me it sounded like valve lifter noise, like you'd hear from a collapsed valve lifter or a weak lifter on a cold morning. However, since it was just as loud when I was underneath the engine as it was above the engine, I should have suspected rod knock. Also, mine started out that it was significantly worse at 2000 rpms and above and reduced in loudness under load or stress. Still, I got 17,000 out of it before it started hammering.

Tony

 

Short out the plugs if you find one that changes the knock you have a problem on that cylinder.

 

I have pretty much determined that it is not a rod knock, but I need help to figure out what it is. I recorded the sound it is making. here are a couple of links to those files. Engine 1 Truck 2 These were recorded with all drive belts removed to issolate the noise from loose accessories. Truck was in park at the time. as i stated before the noise is intermitant and worse when cold. Any help is appreciated. If the links don't work let me know.

Dan pennington

It appears that the redirect from the forum doesn't work right so here are the urls to paste into a new window.
home.comcast.net/~scoutpup99/truck1.mpg
home.comcast.net/~scoutpup99/truck2.mpg

 

It sounds to me like it's valve-train related, like a lifter or a rocker arm. My best advise is to take the valve cover off and see if you can find anything funky in there like a loose push rod or a broken stud.

 

It's your flywheel.

 

How could it be the flywheel? Just asking because I have heard of flex plates cracking but not flywheels.

 

Well, actually it is the flexplate. Technically, it is correctly known as a "flexplate", but in most cases, I don't normally refer to an automatic transmission flywheel a "flexplate".

 

I don't think it's the flywheel because it sounded like it got quieter at higher rpm's. If it was the flywheel, it would have expanded out the faster it spun and would've gotten louder. I had a truck that cracked it's flywheel and it got louder at high rpm's like I said and quiet at idle.

 

I can guarantee you it's the flywheel/flexplate. I've fixed dozens of them with exactly the same sound.

 

I'm hearing an exhaust leak there.Also, are all your spark plugs tight?

Tim

 

Yes there is an exhaust leak and yes all plugs are tight. i just replaced them. all the plugs look good. i am now pretty sure it is the flexplate. the truck made the noise sometimes before the engine was rebuilt in may. i need to also replace the tranny as the previous owner cracked the housing when he pulled the old moltor to put in a junkyard motor. Will the be a major damage to the engine if i continue to run it like it is?? at this moment i don't have the money to replace anything. thanks again

 

Reviving this thread.

I have an engine knock in my 460. Sounds like a tock rather than a tick. (lower tone) and increases with engine RPM. I tried to click the links someone posted with the sound files but the link is not working for me. Was posted several years ago though.

I put a long screwdriver at different places in the engine and it is louder at some places than others. With the naked ear, it is loudest at the rear of the engine (An 1988 E-350 van with engine cover removed)

With screw driver in ear, I hear it most clearly when the business end of the screwdriver is on the intake (plenum?) just behind the throttle body. and under the van on the driver side of the engine block near rear freeze plug (though a bit quieter there than the intake plenum)

I hear it least when the screwdriver is on the valve covers, atop the intake manifold, on either exhaust manifold.

It's a 4x4 conversion van and removing the oil pan is difficult since it's my daily driver. It has an automatic transmission.

Is this detrimental? Do I need to stop driving ASAP? I cannot hear it in the cab (cover on) or when the hood is open. I only hear it under the vehicle, and when the cover is removed.

Thanks
~C