What size sparkplug for Frankheads?

[inspectorcritic]

Z4C plugs will work but there too short leaving a pit think I'm losing compress I need a plug that at least goes flush with the hole but still have about 3/8" before it hits the piston if I got one 3/8" longer will it give me more compression.
What plug number is recommended?
I was think of a 3 prong for more spark.
.. and is I use short the short cap nuts will that risk warping the head compare to the 1"+ plus head nuts?

Can I use , used gaskets got one that's copper?

 

[Sumsloppymeet]

i run a b7hs ngk in mine i was thinking of finding a 3 prong to try out myself

 

[inspectorcritic]

i run a b7hs ngk in mine i was thinking of finding a 3 prong to try out myself

Does that take a 16mm length thread and a 3/4" socket?

Just bought a plug at 17 mm length found out if you run a shorter plug like a Z4C the threads will be damage I'm waiting for a thread chaser to come in the morning to repair it.

 

[Sumsloppymeet]

no takes regular plug socket 21mm i think not sure the threads