Never really investigated the topic of spark plugs too close, but a lot of folks here and on the web recommend AC Delco R45S. When looking up the application, it states that this plug is for a 400 2BBL. The correct plug for a 400 4BBL is suppose to be a R44S and R43 S for high speed driving. I'm sure a 1 point heat range isn't probably gonna make a world of difference, also, things may have changed in plug development and manufacturing, just thought I'd throw it out there. Rock Auto and our manual can back up the info above.
Good subject. Personally, I still locate and use the recommended 44S plug and have never tried the R44S. I know the "R" (resistor version) is used for RF interference purposes but I am unsure if it affects the spark intensity when using my original coil/points/capacitor/rotor.
I started racing before there were any HEI dist. And even in the late 70's, the HEI was only a few years old, and apparently not a lot of racers knew much about 'em. Most still used points. Some went with aftermarket dual points. But I stayed with single point Pontiac dist. I used all Accel parts--cap, rotor, coil, points, & wires.
I used Champion plugs for the 1st few years. But, at 1 race, I had a plug come apart, causing a bad miss, obviously. So, I switched to Accel plugs, and never had another problem with plugs. I don't know who made the Accel plugs, or who makes 'em now, if they still sell plugs.
On some of the other Pontiac forums, most seem to like either NGK or Autolite plugs. I've never done any plug testing, so I can't say if one brand is any better than the other. But, I'm quite sure you can Google up tons of plug reviews online.
Interesting that Champion plugs and AC plugs were made by Albert Champion. His partners in the Albert Champion company won the Champion name and incorporated the champion spark plug company and Albert champion made spark plugs with his initials AC on them as the AC spark plug company. Both products are now ACdelco, owned by GM.
