I just recently stripped my block of all the chevy orange. It was Aervoe engine enamel. I used the Jasco Premium Paint and Epoxy remover (from home depot) with wire brushes and steel wool and it took all day to strip the block and heads....and there was no primer. It was on there.
When I repainted I used Duplicolor engine primer first and then Aervoe again. Important thing is to make sure the parts are clean clean clean. Dont touch them with your fingers after you clean clean clean.
If you decide to use primer first, put it on SPARINGLY...almost semi translucent...just enough to cover. Regards.