Originally Posted by techinspector1
Max pressure for a Holley is 6 1/2 psi at the bowl inlet. Regulate your pressure to 6 psi. No need to run the pressure right up against the wall. More pressure will blow fuel past the needle and seat and into the manifold and create tuning nightmares like you are describing.
Further you may want to upgrade the 600 vac sec carbs needle seat assemblies to the hi flow .110".