Anybody know what kind of rotational backlash is acceptable on the distributor? In troubleshooting by rough running issue I suddenly noticed there's quite a bit of rotational slop in the distributor cam

The tune-up directions say to remove the vacuum advance.

Thanks for the thought, but yes, I did watch the timing mark while revving the engine and it does advance as it should, although it could be the vacuum advance doing it. I hear the centrifugal advance rarely goes haywire, and I'm not sure how to isolate it for testing purposes.

Thanks for the input. It's the same when I remove the air cleaner.

Well, I'm at my wits end over this. About a month ago I noticed my '49 Custom 8 started to run rough when I opened the throttle. It starts to accelerate and then when the pedal gets to about 3/4 to the floor the engine bogs down, it stops accelerating and runs rough. Prior to this it ran fine at all speeds, even at freeway speeds around 75 mph or higher. This is what I've done thus far:

replaced the vacuum advance on the Autolite distributor
replaced the points
replaced the condenser
replaced the coil ( there's a separate post on this in this forum)
replaced the fuel pump
replaced the inline fuel filter off the tank prior to the electric fuel pump ( I never use the electric fuel pump, no need to, I drive the car almost every day)

I set the points at .016.
The plugs look ok, a little sooty, but it runs a little rich.
I rechecked the manifold vacuum and it's a steady 19 inches at idle ( I'm at about 1300 ft above sea level here in southern California). And when I blip the throttle it behaves as it should, dips and then comes right back to 19 inches.

I did a compression test and the pressures were a bit low ( in the mid 80 psi range but consistent across all cylinders.)

I checked the ignition timing and it's right on at 6 deg BTDC, vacuum advance disconnected.

I took apart the carb (Carter WD-O 531SA). I didn't rebuild it because I don't see anything wrong with any of the components that typically come with a rebuild kit. The needle and seat look fine, the accelerator pump looks ok and seems to pump ok. I took out every brass orifice making sure they weren't blocked. I sprayed carb cleaner through every passage I could find. The metering rods appear to operate as designed and they look ok.

I had a very similar problem with my '50 Ford a few years ago and it turned out to be the coil. There were some posts in this forum ( or maybe it was somewhere else, I can't recall) that said you had to be carful about coil polarity so I took the coil off my Ford (also positive ground system) and put it on the Packard and I still had the problem.

Up until this time the car ran perfectly, although around the same time I noticed some tapping noises ( I posted that on this forum also) but nothing really bad, and it goes away after about 10 or 15 minutes of driving.

What could it be???

Well then I'm back to square one I guess. I was reading through the training document for the WDO carb on my car and they have a troubleshooting section and one of the items they mention under High speed circuit complaints is a "restricted drilled vent hole". I assume this is the vent to atmosphere of the float bowl, but I can't find it anywhere. Anybody know where it is?

I didn't solder the wire to the new coil, I just stuck it in between the coil and the bracket. Then when I tighten the two clamps together the wire is pretty secure. But I was wondering if that may create more resistance than the original soldered arrangement.

My '49 Custom 8 is running rough at high revs. I've done everything I can think of to get to the bottom of it but so far no joy. One of the things I did was replace the coil, because I remember having the same problem with my '50 Ford. So I just got a 6v coil from NAPA and I noticed when I removed the old coil it was soldered to the bracket half. So I had to tear that off and I then used that for the new coil. To make sure the coil case was grounded I removed the paint from a little spot on the coil and placed a short piece of wire between the bracket half and coil and ran the other end to one of the bolts securing the one bracket half to the other. I noticed that Max Merritt sells their coils with the bracket half attached to the coil. Did I screw up by buying the generic NAPA coil?

It's hard to tell, but I would guess it's at engine speed. As I mentioned, it's most prominent during acceleration on the road, if you rev the engine while stationary you don't hear it, so it has to be under a load I guess. Lately I notice that the engine is running rough at very high revs ( gas to the floor in second gear for example). I'm going to run a compression check on it tomorrow and I'm also replacing the fuel pump this weekend to see if that helps but I'm not too hopeful since the roughness doesn't go away when I engage the electric fuel pump. The car has really run flawlessly for the past year, and I drive it almost on a daily basis since I retired in April. It's just in the last month or so that I've encountered the noise and now the roughness at high revs.

Thanks to everybody who replied to this. Well, maybe it is piston slap. I've had the car for a little over a year and like I mentioned, it's just in the last month or so that I've notice the noise, I guess the cylinder could have worn funny in that time.