hello guyz i just bought a mac .67. im not sure what the plug is, the plug in her now looks weird. can someone tell me what kind of plug to use in this motor. thank you

OS, McCoy's, K&B will all work.

now as to which number to use will depend on what nitro% you plan on using.

Dan.

McCoy MC-9 real ones not the Dynamite brand labeled MC-9 they are lucky to get to the water. Rossi #7's also are great plugs.
There is a trick I learned long ago. That is heat the plug up then let it cool completely several times before using them. It tempers the coil and they last longer.
If you get the right head shim, nitro content and needle setting a plug should last a long time.

Daniel

There is another glow plug trick that the Brown's use on their engines. Pull the coil out a little before tempering it so that it sticks out away from the plug and into the chamber more.

thank you guyz, one more thing what would the needle setting be i cant find it on the web. i guess ill start at like 3 turns out and go from their. let me know