I put Autolite platinum plugs in my 67 Cougar I'm building right now. Haven't fired it up yet, but after reading this advice I'm having second thoughts. Should I put copper plugs in this engine also? The 5.0L Mustang we have been talking about is computer controlled and has alot more sensors and solenoids, etc.... on it, but the Cougar is a basic engine with a carbuerator. Does that make a difference on using platinum vs. copper????
Platnium isn't better, it's just harder..so it doesn't wear as quickly. Plats were developed for modern EFI engines where it's tough to change plugs and simply for marketing reasons. If manufacturers sell a luxury car that requires less plug changes, people tended to love that idea.
In terms or performance, copper (and silver) plugs offer the lease resistance. Iridium plugs make a case as even being better than plats due to offering a thinner electrode and less resistance that way. Plats are pretty much bottom of barrel.
Modern cars are usually designed for the plats, so the ignition is designed around it. I usually say if it came with copper...stick with copper. If it came with plats, stick to plats. But modern marketing makes people think because plat costs more than copper, then Plat must be "better"...Same deal with premium and regular fuel. Everyone ignores the engineering reason, and just associates higher octane with better fuel.
Which MAF did you install?