Does anyone know the correct gap for these spark plugs?
They have the extended tip for better burn.

Motor is a 540 with Thunderbolt 4 ign.

Thanks

.040

RAPID FIRE AND SPLIT FIRES ARE A RIP OFF <<JUNK ,I had a guy from sterling tell me thursday there like STP for your oil ,But Like
P.T. Barnum(of circus fame) said there is a sucker born every min

But hey run them I'm not slaming anyone for their beliefs I do stupid stuff too !

I can appreciate your concern Cessna but if you compare NGK, AC plugs, Champion Plugs you will see that the Rapid Fire Junk reaches furthur into the combustion chamber hence better chance of not fouling at low speeds.

Most plugs are avalibile in extended tip -
Just for chits and giggles today I compare a rapid fire and a extended tip plug and they were either the same or the autolites were longer ,just my 1 cent worth

and they make tips for oil burners that schroud the tip (hide it ) from the oil and ect in the cylinder not put it out in it ,go with a MSD box and regular plugs you'll think you had your motor rebuilt

bobby daniels with the msd ignition on a 502efi what would you gap the plugs at ? using either ac delco or ngk standard length plug?

Stay with 40 on the plugs ,it (the msd) really helps idle ect and ect. use one of their e type coils or the blaster 2

Bobby,

Good point on the MSD box.
Can I hook the MSD into the Thund IV ignition ? and how do I wire this up.

2nd question... I was told that Autolite plugs were a good choice for my motor but was never able to figure out which one.
Any help here

RJ

sheikman1,
I see the motor is running good. Great to hear. So how does the boat like the 540 ?

Pwrbt33

P.M. your head type and comp.ratio,and cam and I'll be happy to help with plugs ,,,autolite work fine I can get the number with info

shop for a MSD 6al box jegs or summit ,but shop ,hope you do it it will help