1963 327/340 Spark plug

[Irby G.]

What was the original plug that came with the 340hp? Was it the 44? Also, what is the suitable substitute now-a-days? Is it the R45? I see that they also have R45S. I assume the 'S' is for extended tip. Will these hit domed pistons?
Aloha, Irby

[Clem Z.]

Re: 1963 327/340 Spark plug

i have seen it happen so i always index the ground electrode so it is not at the 6:00 o'clock position with the plug installed. just use a magic marker to put a line on the plug in line with the ground electrode and make sure the line is not a the 6:00 o'clock position when the plug is tight. sometimes you have to move the plugs to a different cylinder to get this to happen.

[Duke W.]

Re: 1963 327/340 Spark plug

The AC 45 was the best street plug. The AC 44 is too cold and fouls easily.

Since the AC 45, which is a non-resistor plug, is no longer available, you can use the NGK B4 or Denso W14-U, both of which are non-resistor and equivalent to AC heat range 5.

I you insist on AC plugs, use the R45. Piston dome interference with "S" extended tip AC plugs is not likely with OE machining and the OE double gasketing, but unless you're sure that the block and heads have NOT be milled and the original double shim gaskets or an aftermarket thick composition gasket is installed, don't use extended tip plugs.

Duke

[Irby G.]

Mahalo....

Thanks. Cleared it up for me.