Hey guys. I run a 500" Indy motor in a A body. 440-1 heads, Indy 440-2 intake. With my 4150 series carb It's a steady 5.95-6.05 @112-ish car depending on weather & track. Typically a 1.37 or lower 60'

I wanted to go to a Dominator. So I borrowed an older 7320 Holley and mounted it with a Wilson Manifolds open adapter 1.5" tall. When I fired it early this past spring it fouled #7 plug almost immediately. So I put my 4150 back on and it was good to go. Last weekend was running 6.01 on the 4150.

In the meantime I ordered a new custom dominator from a well known builder. Not saying who right now because I don't need all those carb builder loyalties to come out.

So this past week I put on the brand new dominator. Again with the 1.5" adapter. And guess what? #7 fouling very quickly. Plug doesn't look all that bad but I'm checking them at idle with an IR temp gun and 7 is at 200° while the others are above 500°. Here's a temp check at idle aiming the beam right at the tube about an inch or two from the port.
Exhaust temp check video

I'm running Autolite AR3910's, MSD box, with 35° timing

Any thoughts or guidance on correcting the issue? I'm open to suggestions.

-Thanks