VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Clanking

After replacing the rocker arms and top of the head on my 33 1.5 ton, there is a clanking sound while running. Visually, I can’t find anything. It sounds like it’s coming from the back end of the motor, from the rocker arms, but everything seems to be lined up. I’ve properly gapped it all, pushrods appear in good shape. It gets louder when I rev it. Cylinders all looked good when I had it apart, nothing was done with them outside of cleaning off the carbon build up.

Any tips on what to inspect? It’s driving me crazy. My only assumption is the rocker arms or a pushrod is responsible, but I’m unsure how to diagnose it at this point since everything is properly gapped.

here’s a link to a video to hear the sound: https://streamable.com/tcj7kg

If you remove the valve cover again... and slide the right sized feeler gauge between each rear rocker & push rod...While it is running..., it will stop the noise when it hits the one making that noise... then you know it is either that rocker arm or that pushrod... it does sound like a rocker arm or pushrod noise, to me..... but what do I know...???? only an educated guess... easy to test....

That should read between the rocker arm and top of valve stem.

You might even start it with the valve cover off. That would eliminate one possible source of noise.

I don't know if it would apply to your engine but If you still cant find it watch the push rod cover when running. A bent push rod could be hitting the cover.

Dave

sounds like a bent push rod hitting the side cover ??

I ran the motor without the side cover and valve cover today. Inspected all the pushrods and rocker arms as it ran, felt each one. They all appear straight and none were hitting the block. The clanking remains.

The only part of the engine I haven’t inspected is the oil pan- crawling underneath while it ran, the clanking does seem to be louder beneath, and maybe (MAYBE…?) I could feel something connected to the noise in the oil pan. It’s hard to tell if that’s just acoustics in the garage or not.

Since all of this occurred after a bent valve guide and push rod, could the strike from that broken rod to the cylinder, possibly cause anything to break loose with the babbitt bearings? Could this be the culprit of the noise? I’ve never messed with them on this vehicle, but my father thinks he recalls no shims left. Any thoughts?

I suggest getting one of those cheap stethoscopes with a pointed rod at the end. I bought mine at Harbor Freight for under $20.

Then, while the engine is running, you can 'listen' closely at different locations and better locate the place where the clanking is coming from.

I used one of these tools to locate an engine knock back in 2017 when I rebuilt the '28 engine in one of my trucks. Here's a link to where I dealt with th0se engine knocks: https://vccachat.org/ubbthreads.php/topics/404082/re-resurrecting-a-28-4-banger.html#Post404082

Hope this helps.

Dean

Rustaholic's suggestion is the preferred method a cheap idea is use a long screwdriver against the engine and your ear, it works reasonably well and in some cases better than a stethoscope.
Tony

Thank you for the suggestions. I went and bought the stethoscope from Harbor Freight today, still not 100% I can tell where it’s coming from- although the thing does work really well. I’m going to get a second opinion via my Dad this weekend to see if a fresh ear hears something I don’t.

Update: Best I can tell, even with the stethoscope, is it maybe is coming from below, I might be picking up some sounds from the oil pan, or one of the cylinder walls. It’s honestly hard to pinpoint.

It’s more apparent when revving / pushing down the accelerator than it is at idle.

My only thinking is I drop the oil pan to take a peek underneath, otherwise I’m out of ideas, other than learning to live with it.