Spark plug problems?

[bud45]

Had to change plugs again in the truck today...the truck is a '69 GMC with a '65 283 out of an El Camino. The original plugs were R43, which promptly fouled after a week. No amount of cleaning worked, so the local parts guy said, "heck no, go with R45s...R43s are too cold!" and so I did. Problem solved for maybe four months, until those fouled, too and BAD! I took it upon myself to get something hotter ( fave guy has transferred, no one knows squat any more at local parts house!) and the only thing available were R46SZ plugs. I regapped them to .035 (they were originally gapped at .050) and they seem to work MUCH better- it now acts like 25+ more horsepower & smoother running.

Since I do mostly city driving (top speed 45-50, with occasional 65 mph jaunts for a couple of miles), plugs seem to foul more often. I understand high speeds, like Interstate speeds & racing call for colder plugs...so slower speeds need a little hotter variety- am I on the right track?

Has anyone else had experiences like this? It's been a L-O-N-G time since I've had to experiment with heat ranges, and it was on Mopars 'way back then, not GMs...thanks! Bud

[Robert1970C20rstbukt]

Do you have a points or HEI setup?

[chip46wis]

I used to use r45C-c stands for commercial use-----I went from changing every 2000 in my old 375 horse 396 to about 5000 miles-worked for me-------

[bud45]

Robert, I have points and did a tune-up after the engine was installed last April, but still have had fouling problems. Knowing the source of the engine, and it having R43's in it, I'll bet he jetted the engine a little rich, since I still have some "smut" at the tailpipe. I'm STILL gonna rebuild/replace the carb after hunting season is over on a weekend off & check it out...