W/r/t "The intake side of these heads is limited by the valve opening - not the port"
I disagree.
The ratio of the intake valve area to the cylinder displacement is comparable to many high performance V8 engines. Using the std. 1.875" valve in the 235:
Valve area in square inches 2.76"
Cylinder vs. valve area = 7.0%
For comparison, a 350 with the std. 2.02" intake valve:
Valve area in square inches 3.20"
Cylinder vs. valve area = 7.3%
In my opinion, the port is overworked, and not nearly large enough since the common pair of cylinders causes constant pressure changes, reducing the efficiency and making the port “feel” smaller. This is why
the siamese intake ports of the later Gen-3 engine of similar displacement are wider ovals with far more cross-sectional area. According to author A. G. Bell (
https://tinyurl.com/yb7uahxr), a siamese intake port’s area should be slightly larger than its intake valve area. Using the common 1.875” valve, the port should be approximately 1.900” ID (3% larger area than the valve), which is 91% larger than the existing 1.375" intake port. Of course, this is impossible due to the casting’s limited wall thickness.
My conclusion: the port cannot be made too large.
