[RodgerH]

I have a Blue Thunder dual plane intake with a notched divider under a Holley 4150 with mechanical secondaries. Runs great, flat torque curve, pulls strong from idle to 6000.

I want to add a phenolic carb spacer for heat insulation. I have room for up to 1" thick.

Question: With this notched divider dual plane manifold, should I get a 4-hole or an open spacer?

Rodger