flathead tech question

[zibo]

question 1

was wondering what the difference is in spark plugs
H10, H10c and H12 's.

question 2

what plugs are recommended in a stock flathead, old dual point mallory with BEST coil and 2 94's?

thanks alot!

travis aka zibo

[Mr 42]

I think the H10c is a copper core type
and H12 ha sa differnt heat range than the H10. I will never remember if they ar hotter or colder.
But it doesn't matter since the H10 or H10 C you want.

I have a stock 8Ba with a thicksyun manifold and two Stromber 81's , and a MSD dizzy,

And the H10 works wonderfull....

[Bruce Lancaster]

Also, I believe the C type plugs have superceded the old types in most Champion types, and you can't get the others any more. Pretty sure 12 is hotter. H10 is the usual number for most uses, many catalogs once listed H11, I think because all the flatheads left were presumed to be old smokers needing to burn the oil off their plugs!

[Digger_Dave]

My old Champion Plug Chart shows the higher the number; the hotter the plug.

My AC Chart shows, 45L as the equivalent to Champion's H10 with 47L being hotter.

[Butch11443]

I'm running a "49" 8BA with a Mallory Dual-point & 2 - 94's. I use H12's and haven't had any problems yet. Stock is H10.
Butch

[zibo]

thanks-
actually I scavenged a new set of H12's off a dead merc,
it drove well up to the rc & hr.
seemed like a hotter plug, but ran cool
(on freeway anyway)
thanks for the info!
tp aka zibo