HEI distributor tuning problem

[WadmalawJoe]

Well, the job is not done.....
The noise came back after a couple days. It was warmer last weekend when I set everything. Then it turned colder for the week. I drove the truck everyday last week. So I'm thinking maybe the carb (edelbrock a pos imho) has something to do with it. It has a manual choke so I'm controlling the choke, but the thing never consistently idles the same. So I'm thinking the vacuum probably changes to. I don't know.... I will be adding a vacuum gauge soon though.
Another tidbit of info; I noticed the limiter plate would only limit the advance by 6 degrees at the maximum setting. The advance can was a Mr. Gasket brand that I picked up a couple weeks ago. Yesterday, I took that off and put the other one back on (the one that came with the distributor) I had swapped them around thinking it was a can issue. Right away I noticed the arm coming from the can is slightly different in length. If I wanted to max the limiting plate I would have to jam the arm all the way, which would probably mean zero advance. I set it at the halfway notch and closed the distributor up and checked it out. Timing was at +10 initially, plugged the dist. in and it went to +20, so apparently the halfway notch cuts the advance by 10.
I adjusted the initial timing to +15 and took it for a drive. Well the tapping started at 2,300 rpms and was present through 2,600 rpms. My wife rode with me and says I'm overly paranoid as the tapping isn't very loud. That statement worries me some, because at some point I might hear, the car was only making a little noise before it died....lol
Anyway, I feel like I'm back to square one. At least, I have gained some knowledge about distributors and such, thanks to everyone on here. I will keep picking at it and see what I come up with.
Maybe I should have titled this Joe's HEI and tapping blog....