ive seen soe sheet metal manifold with round runers and some with square. is there q differece? is it like square porting a head, you get more air flowing through it? also what is better as far as plenums. some blend the runners smooth and some have a little "stack" inside of them. like this from full race geoff pic for example.

 

Generally I would definitely think that square runners would be a very bad idea if you have circular ports for the simple fact that you are changing shapes and hitting hard edges both in the runners and the ports. Air doesnt like that! I can't answer your ? about the stacks sitting flush or the ones on full-races manifolds sticking out but I do know that the tapering of the start of the runners is VERY crucial to flow. Air doesnt like sudden changes in direction and those tapers minimize that. Correct me if im wrong somone, but i would tend to think they bring the stacks into the manifold to "bring the air closer to the runners" and to help the air get a head start in the runners to start gaining velocity.........
Hope this helped
Ryan

 

heres some more pics i found.

 

rectangular runners allow for more volume.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Drum and Bass Racing &raquo;</TD></TR><TR><TD CLASS="quote">heres some more pics i found.
</TD></TR></TABLE>

Thats a Mitsubishi 4g63 motor. They have square intake ports on the head, ie the square runners. The honda ports are more rounded.

liam

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liam821 &raquo;</TD></TR><TR><TD CLASS="quote">Thats a Mitsubishi 4g63 motor. They have square intake ports on the head, ie the square runners. The honda ports are more rounded.

liam</TD></TR></TABLE>
ahh i see. i was looking at some ports before i posted that but i was looking at the exhaust side .