Re: Spark Plug Upgrade
John, well said, sir. Unshrouding the spark always worked, as did indexing the negative electrode, or, what there was left of it, was/is always beneficial. Giant plug gaps between shrouded electrodes doesn't.
I had a 1972 Chevy LUV pickup, used the stock engine for years, then went to a small block. When it was still a 4 cylinder, I had a partial loss of power in the engine. I checked valve settings, OK, timing, OK (had one of the first Mobelec electronic ignition conversions ever, worked well), wires, cap, rotor, compression, bent this, bent that, no luck. I constantly read the plugs during the fix it process, no issues, or so I thought I saw.
Well, one session with the plugs, I read them, looked OK, gap was fine, no reason for a problem with them. OOPS, the number 4 cylinder was the one that gave the problems, looked good. Last look at the plugs, I read them, firing end up, no issues. Then, I put the plugs down, sitting on their negative electrodes, and went to get water to drink. Back to the plugs, going back nto the engine. Number 4, looked again, and found the whole porcelain jacket over the positive electrode was now fully covering the positive electrode and plug gap, literally blocking off the spark area. I turned the plug up side down, porcelain slid back into place opening the gap bck up. I did the rotation a few times, the porcelain was completey disconnected right where it mated with the plug body, so, it was just fne new, and for a few hundred miles, then, porcelain broke away at the body junction, shorting down the spark at the electrode gap, but not all the way into the plug, where the electrode opened when it was installed. Spark still worked when the porcelain was all the way down shrouding the gap, making a significantly less contact area with mixture.
A single new spark plug fixed it.
Moral: It doesn't take much to make a serious problem, that even tech guru heros like the one posted two posts up from here, and even a common shade tree mechanic like myself, can easily MISS..