When I ran rossi plugs in the late nineties the comparable plug to a Mccoy #9 was the Rossi R4. Could not blow one ever. The R3 is a little hotter for the 21s. Best plug I ever ran. Pricey ,but quality is second to none. I can't comment on odonnell plugs. I have never used them,but heard they are great. R3 or R4 for 21s,45s and 67s. We ran R6 rossi plugs in a 60scale for along time. After two laps the engine would shut off down the backstretch. We thought it was the servo shutting down the throttle. After changing servos and receivers the problem still existed. After having to many head aches I
concluded it had to be to cold of a glowplug . I changed the R6 to a R4 the engine came alive and ran like a raped ape. Moral of the story its better to run a slightly hotter plug and slightly rich ,restrict water if needed for maximum performance. Rossi plugs give you the durability to work thru these kinds of problems and not prematurely blow. Hope this helps. Dan Mccormick Namba 221
