Howdy Curtis:
I'll give your query a shot.
No, the late model 200/250 heads have enough volume for mild street application. For maximum performance, is there ever enough? The one barrel carb, in stock trim, is the limiter there. The port size is about ideal for throttle response/street efficiency. Too big is just as much of a problem as too small, except at high rpms. Too small can be helped with increasing the velocity. Too big is hard to cover up at low rpms. The Cleveland heads are a case in point.
Any time a dose of Air/fuel mixture has to take a right angle turn, it is not good for flow. The resulting turbulence does help to keep the fuel in suspension, but a a cost of velocity. The 1st hard right angle is at the base of the carb flange. And again at each individual port. Intake vacuum or suction helps the turning process, but the log/plenum adds to inprecise fuel distribution. The final turn is less than a right angle, but it is a downward turn. At that point, the individual ports are some of the best in cast iron head design. They are straight and steep. Once past the log, the port to intake valve window is almost a straight shot. V8 head designers are always raising the ports to make the short side turn less severe.
The Austrailian 2V and Argentine heads make significant steps to remedying the sharp, right angel turns. Both use a sweeping, indivicual runner from the plenum under the carb. The long sweeping manifold port runners add volume and help to maintain velocity. The Oz manifold falls short, in my opinion as it orients the carb with the throttle shaft perpendicular to the crankshaft. This adds to fuel distribution problems by directing flow to one half or the other.
The height of the inline six is its own worst enemy. Ideally, If the manifold could sit the carb about 8" higher, the manifold runners could bend down too and lessen the angle of the downward turn. That would require one hellacious hood scoop.
The exhaust is severely impeded by the cast in turn where the exhaust manifold bolts on. Milling off the intake log also solves this exhaust restriction.
As long as you're redoing the head and intake manifold, how about moving the spark plug in, closer to the center of the bore, creating the kidney shaped chamber for swirl, and adding a set of piston with a dish that mirror the chamber shape. That would give the highest ratio of quench to bore.
That's my thoughts. Enjoy!
Adios, David
