SBM Edelbrock/Speedmaster Head Data

I agree.

On mildly reworked factory SBM heads, if you don’t do a fair amount of SSR layback, it’s not at all uncommon for me to see the flow continue to drop after the separation starts.
In other words, the flow gets worse and worse as the lift increases.
This is obviously not a problem with the area at the pinch getting worse as the valve is opened further, but rather the area of the bowl/throat getting progressively shut down more as the valve is opened.
In this scenario, if opening the pinch “more” exacerbates the situation, then imo, it’s not helping with power output.

It would make for an interesting dyno test though.
Bigger pinch with more separation and less high lift flow vs a smaller pinch with less separation and more high lift flow.



Not taking into account the corner radii, theoretically enough for about 330cfm.
I meant in a running engine that if the rest of the port was up to the task for (cid x rpm x ve%) that the pinch area should to be sized (it's generally the mcsa) for the application (cid x rpm x ve%) so it don't choke off before desired peak rpm and have decent over rpm (shift points). More so for that then any flow increase that may come from it. In other words if the push rod needed to be moved it would be for the needed mcsa more than an increase in flow, far as I understand it.