non-projected tip. I’d like to stick to projected tip.

that is the correct tip, size, and has crush washer but it’s a heat range 5. I could probably do some crossing and find a 7 off that.

Colder is a 3923, but with your compression if may just foul on cold start

3924 should be fine with your build and heads NA. If a doubt use the 23 but don’t believe you’ll need to. Won’t hurt anything during break in with fluctuating rpms to help cool the cylinders. I’d just ck the plug on the hotter cylinder periodically. Likely #8 or refer to dyno sheet if you did so.

ya for some reason I thought you were running a blower

my concern with going colder is, ever since I bought this damn boat, I started with a 7 I believe on the 502 and it absolutely hates cold start. If I give it one extra pump of the throttle, it will damn near foul all the plugs before it starts. Sometimes does fowl them all and I have to change em out. I’ve been thru the ignition system, carburetor several times, cranking timing check several times....everything is ideal. When I did this build, I just put 6’s in it cuz that’s what I had laying around for the 502 (was gonna switch back to the 6’s on the 502). Well, this setup starts cold flawlessly with exact same ignition, carb, and timing so I’m thinking the 7’s were just too cold although, from my understanding, the “fire” will be the same temperature regardless of plug temp. The plug temp only is referring to how fast the plug will dissipate heat which doesn’t seem like that would even be a factor on an initial cold start.

It disapates heat but the plug needs to get hot enough to keep itself clean. I think it was the NGK site that I saw a nice explantion of proper heat range selection.

sounds weird to foul what ignition are you using?

BKR7E’s. If too cold, they shouldn’t be, BKR6E’s
V-power NGK’s for the win baby.
5/8 hex
.750 reach
14mm thread
.035” gap
projected
crush washer
v groove

I use acdelco’s with iron heads(autolite with iron heads and nitrous ) and ngk v powers with aluminum. Why ? Always always worked for me. That’s why. Others experiences may vary. And probably do. Lol.

it’s all performance distributors brand. External distributor mounted module type of deal. I know it’s not top notch but I’ve seen a lot of people run it.