The design elements of cutting edge racing engines really have not changed that much over the decades. Some refinement to be sure. But the big advances have come with material science, and the increased rpm better parts allow.Historyboy
Aren't motors flowing lots more now through the same size ports at the same RPM? CFD and all, ya know?
Well . . . . NO, not lots more. SOME improvements, yes, but at any given, sensible gas speed and pressure differential, only so much air can flow through a given orifice size.
For normally aspirated engines, let's use the ubiquitous small block Chevy as an example. If you set the standard at the old design, double hump, straight plug, 2.02 "fuelie" iron cylinder heads, even the next series, the iron, angle plug, no heat crossover passage, 2.02 turbo head consistently outflows the baseline and produces more bhp. Newer designs from AFR, Brodix, Dart, etc, whether in iron or alloy, flow even more air. But ALL fall short of the potential flow of a theoretically perfect valve at a given diameter. That's just the nature of the "poppet" valve.
So how did the improvements come about?
A/ Well, CFD development of port shapes played a part,
2/ Reduction of valve angle to bore centerline is huge, ie: reduce angle from 23 degrees to ? ? ?
d/ Valve "cant", in some instances can increase flow, but it also can add "swirl",
y/ Alteration of the port entry angle to bore centerline is also huge,
z/ etc, etc . . . . .
I'm not saying that the improvements are not significant, because they are.
The "new" designs are better because the old designs were pretty bad, based on what we know NOW.BTW, the "old" designs were not "purposely" bad. It is important to note that the designers were working on a production engine, not a "clean sheet" racing engine. They were constrained by a variety of factors such as "packaging space" and "cost considerations".
Fordboy