BB Mopar head design ??

Jim Lusk said

Every design is a compromise of one sort or another. Changing the heads much would have meant a redesign of the intake and exhaust (expensive). Rocker arm length, pushrod angle, etc. might be more difficult to get right. The original design easily made enough horsepower to be competitive through the production life of the motor.

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So then was it a geometry issue with the valvetrain or something? Still trying to understand why they put the valves where they did when they first design the engine; moving them in would even have had the benefit of making the engines slightly more compact on the outside. I can't think of any good reason to move the valves away from the center of the bore except for some kind of interference with other parts in the engine.