Originally Posted by rv6n6r
I'm not an expert on ignitions so I'll leave it to others to say whether .029 is okay. However I don't find them hard to gap, I use a piece of .032 AL to check it and some smooth jaw needle nose pliers to tweak the gap.
I guess I am the only old guy that worked on cars when you had to gap points and plugs, and thus needed a couple sets of wire feelers, as well as a set of flat blade feelers to set valve clearances. A flat piece of metal will work if the plug ground electrode is flat metal beyond the center electrode, but round wire is better, since the electrodes rarely wear to be exactly flat. However any electrode that is parallel to the center electrode, like aircraft plugs requires a wire gauge. Also, using aluminum, it will get thinner after checking a number of plugs, since the electrodes are a far harder steel alloy.
The gap needs to be proportional to the voltage the ignition generates. That is why plugs with magnetos use .016-.018 gaps. Most '60s cars with distributors and a single very big coil used around .028. Modern electronic ignitions generally use around .032-.045.
Difficulty in gapping is indicative of how hard the alloy is. Iridium, platinum or similar plugs will be more difficult than straight steel.