The differents between spark plugs

[By-Tor]

I understand that there are spark plugs TR drivers use and abuse.lol
My question is about the different metals used in the spark plug.
Copper, Platinum, or Iridium and so forth. Which are these better and in what situations are they better in?

BTW, has anyone herd of the AC Delco Rapidfire spark plug?(There like five bucks at the AZ.)
Also I have been hearing about the gap of the Delco 44's, 43's, and 42's should be .035. Why, is this better than stock?(or is it stock???)
What would be the best in my 1978 Regal S/C?

 

[By-Tor]

Here, let me state more about my TB. Its a stock car with a stock engine. What I want is more efficiency not really power, but if it comes along with the ride I'll take it.

 

[SS/GNX]

In a turbo/supercharged/nitrous car I would stick with copper.
The platinum plugs can melt (well the platinum coating can)
and Iridiums are a POS and also dont work well with un-naturally aspirated engines.

Some people might argue about the iridiums, but my LS1 car got slower on iridium plugs, so I dont like em. my 2 cents worth.

Gap is because you dont want the spark to blow out. If its too far apart, it can blow out under boost, if its too close, it wont effectively burn the air/fuel mixture in the combustion chamber.

Cant comment on the rest.

 

[Alky V6]

I have to disagree about the iridiums. They resist fowling much better and have been lighting off some very rich alcohol mixtures for me. I don't plan on going back to regular plugs. I saw no performance difference from going to iridiums.