Does the groove play any functional in the design? In the casting to the far left in your photo, the groove looks like it creates another site for fastening the manifold to the head. I take it that the grooves don't extend inside the runners, where air flow would be affected. If the grooves have no function, then I think the manifold has a cleaner look without them. In either case, they look wicked.
This is GREAT, guys... thank you for all the replies.
Brian, it looks like you and I are out-voted by quite a margin.
so, no groove it is
No, W-motorhead, no function, and no effect inside. Just mimicks the countour of the inside. Yes, I originally created the provision for the center bolt, but later realized that on the small port, it's not critical. Not to mention, as orginally intended, this small port version has the material to raise the tops of the runners to match large pot heads... thereby creating a more "conservative" option for guys with large ports.
The large port manifold WILL use the center bolts.
Anyhow, just got back a few miniutes ago, with my prepared "333" truck heads. Valves seats are VERY nice, with the blend into the bowl done with a cutter, creating a super rounded contour into the bowl.
I'll be calling my dyno guy in the morning, to make an appointment.
Over the next few days, I'll be pretty busy
If I were in the market for a one 4 intake manifod I would prefer one with the groove because the groove makes me think of one intake manifold runner for each head port but the smooth makes me think of one big intake manifold runner for two head ports like (I think I remember) some 6 cylinder engines and maybe Pontiac 301 V8.
Well here I go again, as we march along, most everyone is out of step but me.
I think it looks good both ways. My preference would be the 5000 with the whole for the bolt looks better with the groove and the 6000 looks better without. It wouldn’t sway me one way or another though.