MSA 6-1 Headers Flow Rate

[Patrick Berryman]

Has anyone in this forum flow tested an MSA 6-1 header before? I'm curious how many cfm their headers can flow and if it's enough for my engine. It has 1 1/2" diameter equal length primaries to a 2 1/2" collector. The primary tubes have 2.36 square inches of room for exhaust to flow (x6) and the collector/downpipe has 3.93 square inches of room for exhaust to flow which tells me that the 2.5" downpipe would become a restriction first before the primary tubes become a restriction. If that is the case, what is the total flow capabilities of a 2 1/2" downpipe and would that mean that the only difference between different headers is the type of bends and the length of the primaries for scavenging effect? Scavenging effects aren't my main priority, but I'm also curious what rpms do the MSA headers have a scavenging effect? I'm currently running an attempt at a port job for the cast manifold, but as I'm sure you all can predict, it is still horrendous and begins restricting around 4700RPM. Thanks. 

[JMortensen]

Never done a flow test, but thought I'd chime in to say that my square port header, purchased from Arizona Z Car in the 90s but same header, had the tubes formed to meet the port shape incredibly poorly, and the inside of the primary was pinched down enough that I actually felt the need to port the header a bit on a couple cylinders to try and open them up before installing it. I'm sure a round port header wouldn't have that problem. I was still pretty green back then, I think today I'd probably beat the tubes or maybe use two prybars in the primaries to spread the tubing back open again and then grind and weld if necessary. I just remember being very unhappy with it.