Trying to help get info on what plug to use with a set of 440 source big block heads. What do you run? What is the part number for Champion and Autolite? Thanks for the help in advance!

try some autolite 3924's. easy to come by and you can move up or down from there.

What combo and compression? I run only NGK`s cos they`re easier to get a full reading on and live well street/strip and for my 12.1.1 comp. 470 w/alum heads I run a # 7 or 8. 7`s stay a bit cleaner and 8`s are colder for full boogie blasts if engine temps are above 180-190.

Need more info.. street or strip, compression and what
fuel.... but autolite 3924 is a decent number.. thats
the full strap.. they offer the race version also which
starts with a "R" which is a short strap

Its probably in the 9to1 area just street strip deal but didn't have a clue on the part number since he had 440 source heads. My friend likes champ and autolite. Thanks for your help!!!

Maybe a 12yc champion then...............

For my 10:1 compression street car with Stealth Heads, these seen to work good:

NGK #2756 plugs (Plug Part # BKR6E-11) which is a 6 Heat range.
The Plug part # breaks down as:
BK = 14mm thread, 5/8" Hex ISO Type (shorter ceramic part)
R = Resistor Plug.
6 = Heat Range.
E = 3/4" Thread Reach.
-11 = Spark Plug Gap of 0.044"

The #2 plug is pretty close to the inner fender on my Coronet, so I also use the special Snap-On spark plug tool:
https://store.snapon.com/Hand-Sockets-So...ex-P644223.aspx

Just had this same problem - car was running like crap.
Last owner apparently couldn't figure it out & first mechanic also had no idea.

I finally found a guy who knows these cars - he said to use RC12YC because they are longer than the stock ones.
(The 2nd digit "C" is different from the stock part # which I can't remember off the top of my head right now.)

Problem went away immediately.

I used Champion RC12YC in mine and they worked perfectly!

When I crossed referenced the RC12YC to NGK it lists several heat range 5 and 6 plugs, including the BKR6E that I'm using, so I think the heads like the hotter spark plugs. I orginally had cooler "8" heat range plugs and they fowled when the weather got coolder, that is why I went to the hotter plugs.

For a low compression pump gas motor with those heads i would start with either the Champion RC12YC or the nextstep hotter one, if champion offers them On Auotlites thier # 3325 will probaly work okay also

Thanks everyone...