[bigblockv6]

The problem is as I mentioned previously the smaller port heads are not machined to accept the larger port manifolds, therefore the mating surface is uneven, it will not seal up and it will leak:pullinghairout. You will get the same advantage with the small port I beam manifolds used on 351C, 379 and non Magnum 401 & 478 engines as you will with the larger Magnum manifolds as both style manifolds have the same free flowing design other than at the mating of the ports. How much more do I have to make this clear to you???