Not your normal Mopar cooling issue

What are the spec on your cam and what centerline did you install it at?

More likely your ignition-timing is retarded
And the exhaust leaving the cylinders is still burning, and still expanding. And jamming up in the logs. Then on the overlap cycle, the HOT high pressure exhaust is racing across the piston and up into the intake, which is at waaaaaay less pressure.
And around and around and around it goes.

Here is your proof; the first few inches of the intake runners will be coated with a thic, cooked-on layer of black soot.

Here is your cure; With the car stopped and brakes locked, rev the engine up to cruise-rpm and hold it there. Then grab the distributor, and advance the timing until the rpm no longer increases. Now read the timing at your cruise rpm. Subtract 3 degrees and Write it down!
Let the engine return to idle and put the timing back to where it started.
Now, go figure out how to get that written-down number of cruise timing, without affecting your PowerTiming, and make it happen.