I've been through the internet and I can't find a consensus. When someone asks this question everyone says I like Champions, I like NGK or I like Autolite. But they don't tell which plug number they're running or how their engine is set up. So here goes.

It's an iron head, 9.75ish compression 360 based 408 stroker. I have a Pertronix distributor and a Pertronix coil. Pertronix says to gap the plug at .070 MORE than stock. So I guess the gap will be .040-.045.

This will be in a Duster that will mostly be cruising with a couple of blats down the track per year.

Thanks

I run autolite 65’s in my 12.2 :1 x head gap set at .038

So that's a Champion RN12YC. That would work for me and is what I was considering. I thought that with that compression a cooler plug was called for. At least that's what I gathered during my keyboard jockeying.

Do you find that it runs better or the Autolites last longer than a Champion?

Thanks

I typically run 3924’s on my 416 stroker. Last time, I tried 3926’s and nothing got better. I think the 3924’s ran better.
274-S comp solid cam
9.7:1 comp
Ported edlebrock heads
M1 single plane
BG silver Claw carb “advertised” at 750. But bigger than an old school Holley or carter 750
TTI headers
Automatic stock 340 converter

I run errands around town in it.

I ran a couple sets of champions... then switched to Autolites. They last longer, smother idle, slightly better cold starts.

On your deal with the iron heads and that much TRUE compression I would run either a set of Champion RN9YC(13/16 socket size) or RC9YC(5/8 socket size), both plug # will work on your heads
On the Autolite plugs I would start with a set of #64 or the newer resistor type # 3924 or maybe a set of 3925 and see how they work for you
Not knowing the type and octane rating of the pump gas your going to run limits us on our guesses

Thanks for the replies. We have 93 octane which is 10% ethanol.

I agree with Cab; I prefer the smaller 5/8 hex, and would run the Champion 9 or 12 heat range & see how they read.

As dumb as it is my father liked autolite and not champion. How’s that for hardcore real life. technical data! I have had good luck with the autolites though.

I’d run an NGK BPR6ES gapped at .035, or it you want to get fancy a BPR6ET with the gaps as they come OOTB.