don's right on the money. my problem was not being able to keep the secondaries closed and them big suckers can destroy millage quick. had a friend who was an ace on them but sadly he passed. not too many out there that can get them right any more. to be honest had i not already had an intake i was going to run a 2 barrel on my shop truck. the 390 and the 450 holley's work really good for small street motors.