[Longs]

1967 GTO, original engine, rebuilt about 20K miles ago.. Original distributor, 100K miles, still running points.

I have a rattling sound at about 1,000 RPM, idle speed in Park, seems to be coming from the distributor. If I shift into drive and the idle drops, the noise goes away. At higher RPMs I'm not hearing the rattling noise. It has been doing this for some time now, thought I'd see if I could figure it out.

I have checked the cap and rotor, mounting screws on the points, etc. and I don't find anything loose or obviously wrong.

I have links to two videos. One shows the play in the distributor with the cap off, moving up and down and back and forth by hand. Does this play look "normal" or is it excessive? I'm wondering if the distributor is "floating" at idle, but nothing I can see rubbing.

The second is with the car running. As I work the carb and allow the RPMs to return to idle you can hear the rattle start and stop.

Can anyone diagnose this? I've never removed the distributor myself, I don't know what should be normal. Thanks for any help anyone can provide!

https://youtu.be/4V5-33fSSv4 Distributor Play

https://youtu.be/Cx9OK5loqQ4 Distributor Rattle

[Holeshot71]

Could be the pcv valve. Check to see if it's rattling when making the noise?

["QUICK-SILVER"]

Up down looks a little much but I've seen worse.

Twist in the centrifugal advance looks normal.

Might be something up with the vacuum advance. Right where you're working the throttle is where the vacuum advance would be coming in and out if it's hooked to a ported source. Easy enough to unplug the hose from it and see if the noise changes.

Clay

[steve25]

Are the advance springs shot?
Remove the springs and advance weights and rev to 1K is the rattle or whatever still there?

[Longs]

Thanks for the replies, found the rattle. It is coming from the vacuum advance rod that goes from the diaphragm to the plate in the distributor. If I reach under the distributor and put a little bit of upward pressure on the rod, the noise stops. I can feel the rod moving in an out with the throttle, so I'm assuming that it's able to rattle either based on the rod going into the advance plate or in the diaphragm end of the vacuum advance.

At least now I know that it isn't coming from somewhere down in the engine.

Is it necessary (or easier) to pull the distributor to change the vacuum advance unit?

[TedRamAirII]

You CAN do it without removal. But I would pull it out, detail it, and replace it all in one shot. Replacing the Vac Advance may move your base timing, if the rod isn't exactly the same as your old one. You will need to verify ignition timing after you are done, anyhow. I wonder if its rattling because its getting a weak vacuum signal using Ported Vacuum? At idle, it really should not get any, unless the throttle is open too much? Once you pull it, you can see why it rattles. Glad its only that!

[lust4speed]

Is the plate itself pretty firm or does it have slop? If the very fine C-clip is missing from the center top of the plate it will move around. Only movement should be circular with really no up and down movement.