Hey All,

Got a chance to pull the plugs this weekend and shoot some oil in the chambers to get the rings lubed up. Have a question about the plugs I found.

They're Royal Blue Crown spark plugs, 1 & 2 were M-5 and the rest were M-7. Looks to be different heat ranges, does anyone stagger their plugs like this? Anyone heard of Royal Blue Crowns?

Thanks,

Many manufacturers or brands of plugs were available in the 1930s. AC made Blue Top plugs and several other companies tried to copy the distinctive feature in order to confuse customers and sell more plugs. Still happens today!