[cash]

Hey all,

Narrowed a noise I've been trying to track down to the distributor. When the engine is hot, after 15 or 20 minutes of driving (and oil nice and thin?) I can put a stethoscope on my distributor and hear a clackety rumbling. Figure it has something to do with the distributor, drive gear, or oil pump. The problem is, I have zero current knowledge of what's going on inside that hole (but I am learning). Appreciate you taking a look at the video linked below. Just a video I took looking down the distributor hole.

By the way, the distributor is some kind of HEI type conversion. The gear on the distributor looks to be in good shape, with only the slightest signs of rubbing in the center of the teeth. What else.... Posted in another thread that I found gas in my vacuum advance canister. Working through that. Assume that they are unrelated but I could be wrong. The engine is a stock 289. It was rebuilt or freshened up prior to me owning the car (not sure of extent of work done). The noise is slowly getting worse. The engine now has a little shake now whereas before it was fairly smooth.

Can't think of anything else. Thanks for looking.
Sean

https://youtu.be/VVSxLZmfyRU

 

[GypsyR]

The only thing in there that jumps to mind to me that would make such a noise would be the timing chain.

 

[gt350sr]

Nope- not seeing anything funny in there...... lol (Sorry- couldn't resist!) >

 

[cash]

Ha! That's great.

Quick comment on the gear on the distributor. Is it supposed to move? It has some up and down play which I hear is normal, within certain tolerances, but it also wobbles. I mean if you grab it by the sides between your thumb and index finger, you can rock it a little back and forth.

 

[cash]

Oh, and to Gypsy, I did check the slack in my timing chain by rotating the engine over by hand and marking the amount of degrees that you can go back before the distributor wood start moving. I can only move it like three degrees which I understand was good. Of course I could have done something wrong and there could be more slack but it didn't seem terrible based on the research I did.

 

[Turnall]

Ha! That's great.

Quick comment on the gear on the distributor. Is it supposed to move? It has some up and down play which I hear is normal, within certain tolerances, but it also wobbles. I mean if you grab it by the sides between your thumb and index finger, you can rock it a little back and forth.

When I first read this, I said NO WAY...but I have a brand new MSD 8579 on my desk and I can move it side to side a little as well.

Allen

 

[macstang]

Is it just the gear wobbling or the whole shaft? I'm guessing it is the whole shaft in which case it would be most likely the bushing that the shaft rotates inside of is worn out. If it is just the gear itself wobbling that is another level of issues and concern. The gear itself should not move at all. It is pressed onto the shaft and then pinned with a roll pin to prevent just this very thing from going on.


If the shaft has been wobbling chances are good that it has also grooved up the electrodes inside the distributor cap so you probably should plan on a new rotor and cap along with either having the distributor rebuilt or just getting another one.



Another source of a clacking noise inside a distributor happens when an advance spring comes off its weight or it breaks. The counterweight is no longer being held properly and it will clack around like that.

 

[macstang]

Ah you were also the gas in the vacuum advance. My first thought was a porosity issue with the vacuum channel in your carburator. These things are cast after all and you can get a bubble that will let air into where only gas should be and gas into were only air should be. The other thought I had was if your vacuum advance is leaking badly it might suck some gas up in there because it should only hold vacuum or release vacuum and not continually draw air through it. Easy enough to test the vacuum advance. Just suck on the hose and if it doesn't hold a specific suction the vacuum diaphram is leaking so its time to replace the canister.

 

[Huskinhano]

What the others have said. The gear should ABSOLUTELY not move on the shaft!

 

[cash]

When I get home this afternoon I'll shoot a little video of the distributor and show you all of the wobbling parts. Yes Mac, outside the fuel in the vacuum advance post. Assuming these things are unrelated but maybe not.

Down inside the hole there's a hex shaped shaft which I assume is the oil pump Drive, correct? Should that have a little play side to side? The cavity is sitting in is solid but if I poke the oil pump shaft with a stick it does move about in its hole.

 

[macstang]

The hex shaft drives the oil pump and will have a little play in it just sitting down in there. The distributor shaft slides over the end of that thing and takes all that out.

 

[Tony 64]

The rumbling that you hear could be the fuel boiling in the carby and the noise is being transferred through the intake manifold.

 

[JSHarvey]

No idea on your problem, but I wanted to say that you've got a gorgeous car!

 

[cash]

Thanks for the ideas and compliments. Wish I could take credit for the color but that was my dad's idea.

Regarding the fuel boiling, when I listen to it with a stethoscope (placed on the cap) it sounds like a simple clacking. It also stops immediately when I cut the engine.

New video:

https://youtu.be/ocBBjx-L_OY

Thanks again

 

[Caper50]

Why not pop the distributor back in and take a video once the noise reappears? Might be easier for someone here to help diagnose. Just a thought.

 

[cash]

I'll give that a shot. Tried it before but it's hard to hear on camera. I can make it out but I know what I'm listening for. I'll figure out some way to transmit the stethoscope vibrations to the camera microphone.

In the meantime, I took my borescope camera and took a few pictures, colonoscopy style. Not sure if they are actually useful, but neat to look at. One pic of the oil pump drive shaft, one looking back at the timing chain, and two of the distributor drive gear.