With so many plugs on the market one could go crazy trying to choose.

I have a 1970 440-6 and currently I'm running a Champion RJ12YC plug in it. They've been in for awhile and have decided to a tune up.

Any recommendations out there on manufacturers and plug type?

I'm also considering going to a little "hotter" plug so wondering if there's an Pro's/Con's in doing this and what would be the choice if I did that? The reason I'm considering a higher heat range is that the plugs look a little dirty/fouled which could be a carb adjustment?

Your thoughts ??????

NGK. XR5

Yes NGK has gotten some good reviews here lately. Wallace raceing has good plug reading pics. unleaded gas shows less color than leaded gas used to. I have one of those "colortune"kits that has a modified spark plug you screw in & it has a clear glass section down on the firing end & you can see the color of the flame! the sheet says you want a nice blue. trick as hell! Choke on too long is a common problem. I would check the carb & get the timing dialed in (timing first).

If the Champions have worked OK maybe use the same? I like and run NKG's based on the (no longer posted) guidelines for plugs from Mancini based on compression. They have worked well. Plugs look good if I pull them after running. Not so good if pulled after idling a lot cold. A hot(er) cam and idling, especially cold, do not go together well

If the deposits on your plugs are blackish and rich mix fuel related, a hotter plug may not help much... and also may promote detonation. Those are some "pros and cons".

Your far better off in fixing the tune (probably jetted richer than needed) instead of trying to band aid it by using a spark plug heat range that is to hot for todays fuel
Do you know what the List numbers are on your carbs or if they are originals or replacement carbs?
If you know or can looked at the list #s on them and post them on here then we can look up the stock jetting for you and post it back on here

I have wondered if i could install a Colortune
and then aim my Harbor Freight video boroscope probe at the window of the Colortune,
and view the flame color while driving the vehicle.

I have heard that one challenge with the Colortune is squirming around to be able to get a good look at the window.

Spark plug choice wise,
the irridium tipped NGK's
set to the biggest gap your ignition can fire at redline rpm,
Are good value for the money,
and last a long time.

I run NGKs in my cars At the shop we used them a lot and no problems.Usually we ran ACs in GM though.Bosch we would not install even in an enemys car.Total trash in my opinion.saw too many that were trash in different cars.Older mopars we usually ran Autolites but Ive run NGKs for at least 10 years now.Rocky

I had been running autolite copper plugs but I think they're now made in China

Thanks for the replies. Ordered a set of NGK XR5's today and will address the fuel mixture. Rebuilt one of the original carb's a short time ago but really didn't spend the time on "fine tuning" the carb(s).

Will running a gap of 35 be good for these or do you have a better suggestion?

Yes 35 is good. the Jacobs ign bible has recommendations on going more/less than that for special tuning but you will have zero issues with 35