SBC HEI Distributor clicking loudly and timimng won't stay set where i put it.

[AyWoSch Motors]

Okay, very odd question here. I'm sure I'll be told I need a new distributor, but curious what is going on.

So I have my 350 on a run stand so I can check everything out before it goes in my truck. Yesterday I hooked the exhaust up so itd be more quiet, so I could hear everything better.
Started up nice and quiet, and that's when I noticed the distributor is clicking pretty noticeably. The engine runs okay, but I do notice the idle isnt as smooth as it could be, and it has the slightest stumble on first rev from low RPM.
So I got out the timing light, unplugged the advance and capped of the vac port.
Timing was a little retarded, which I tought odd because I had set it before to 0°.
So I advanced it until it was reading about 8°- 10° BTDC at low idle and more about 12° at high idle. Engine was happy and had snappy throttle. Then I checked it a few moments later to be sure, and it had gone back to 0°. I advanced it once again just a little to see if itd stay, and sure enough it went back to 0°. Dont have a clue why.
The distributor hold down is tight, and it wont move at all when tightened down so I know it's not slipping, and the in a different position then when I started, so it has to be advanced, but its not reading that.
I plugged the advance back in, and its running fine. I let it idle for a while to hear it, and the engine is healthy, but the distributor is clicking alot.

I'm thinking of just buying a new one. But wondering why this is doing that, never heard anything like that before.
Dont know if its original to the truck, or something the PO put on, but shes old.

Please help, thanks.

 

[pnwnvrdn]

Pull the cap and rotor and inspect..cracked?, interference issue?

 

[mtnmankev]

Ayden,
More than likely you are looking at a new distributor to fix the issue.
I have seen the inner shaft slip on occasion, sometimes it's the roll pin that fails and the gear stays meshed with the cam but the rest of the dizzy is out of whack.
Not that anything weird EVER happens in my world to show me things I could not have imagined ..........

 

[Vbb199]

You mentioned unplugging vacuum advance, then setting it at 8-10 and it running, but it returned back to 0 when you.... plugged vacuum advance back in? Or just maybe wicked the throttle a couple times ?

You don't have the vaccum advance nipple on the distributor capped off do you?

I did that mistakenly one time and had all sorts of wacky results, between turning the distributor wayy up to crank it, Cold, then turning it way down retarded to keep it from lean popping at WOT, operating temp.

 

[Vbb199]

Though that clicking makes me think your weights are intermittently slinging out or hanging up, what's going on under the cap ?

 

[mtnmankev]

Though that clicking makes me think your weights are intermittently slinging out or hanging up, what's going on under the cap ?

Hopefully it's something simple to figure out and he won't have to deal with any spirits or space aliens.

 

[fast 99]

Previous suggestions are where you should start. Might add I have seen oil pumps that were not machined correctly and have tight spot. It will cause the distributor to "rattle". If a stethoscope is handy the noise will be more obvious in the pan. Hopefully that isn't the case.

 

[AyWoSch Motors]

You mentioned unplugging vacuum advance, then setting it at 8-10 and it running, but it returned back to 0 when you.... plugged vacuum advance back in? Or just maybe wicked the throttle a couple times ?

You don't have the vaccum advance nipple on the distributor capped off do you?

I did that mistakenly one time and had all sorts of wacky results, between turning the distributor wayy up to crank it, Cold, then turning it way down retarded to keep it from lean popping at WOT, operating temp.

I only capped off the Vac port on the carb with a plug, left the advance port on the dizzy open to free air.

And it was seeming to return to 0 when I was messing with the timing, while the advance was still unplugged. Only plugged the back in later.

Seemed to happen after I revved it.
I set it at low idle, then a fast idle, then I did an RPM sweep to watch it move up as it should and listen to it. After I let off, and it backed down to low idle, is when I noticed it went down again.

 

[AyWoSch Motors]

Previous suggestions are where you should start. Might add I have seen oil pumps that were not machined correctly and have tight spot. It will cause the distributor to "rattle". If a stethoscope is handy the noise will be more obvious in the pan. Hopefully that isn't the case.

I did put in a new oil pump, but it sounded healthy when spinning it by hand pre-installation, and it sounded fine when I used my oil prime tool and spun the pump.

I leaned down under the pan while running, no sounds coming from that area. You can put tell it's coming from the cap, its very noticable.

 

[AyWoSch Motors]

Though that clicking makes me think your weights are intermittently slinging out or hanging up, what's going on under the cap ?

That's what I thought, maybe the centrifugal advance weights broke the spring or have slop in them.

I'll have to go out and look at it more carefully.

 

[AyWoSch Motors]

Ayden,
More than likely you are looking at a new distributor to fix the issue.
I have seen the inner shaft slip on occasion, sometimes it's the roll pin that fails and the gear stays meshed with the cam but the rest of the dizzy is out of whack.
Not that anything weird EVER happens in my world to show me things I could not have imagined ..........

Hmm, never would if thought of that, but that's possible. That could explain it.

 

[fast 99]

That's good, just tossing it out there. A noisy/bad pump is something that can be easily overlooked. Have seen it occur more frequently in the last few years. Had to replace a pump 2 motors ago.

 

[mtnmankev]

Hmm, never would if thought of that, but that's possible. That could explain it.

That exact problem shut down one of my trucks a few years back, in my case the dizzy shaft slipped at the top, it's basically a friction fit.

 

[AyWoSch Motors]

Here's the cap and rotor. Everything looks good. All points look healthy, shiney, not burnt out.

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I did notice that there are points in the cap that look like they've interacted with the rotor...

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And I noticed that the tip on the rotor looks bent down? Dont know if its supposed to be like that or not...

 

[AyWoSch Motors]

And here are the weights. Nothing is broken, or particularly put of wack, but it's a little sloppy.

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Did notice theres quite a bit of up and down play on the shaft. Maybe 3/16 play up and down. Is that normal?