Why is the B18 manifold recommended so often when putting a B20 (with SU carbs) in a 122? Based on postings from this board a few years back, I once cut the intake off a B20 combo manifold just to get a dual-port exhaust: I was advised the intake was "junk". Now rethinking this for new engine. . . Volvo engineers must've had a good reason for adopting combo design: this is a difficult casting to mfr.!! B20 style seems to have much better flow porting. The intake manifold was seperated from exhaust again in 1970s only after dropping carbs and going to FI. . . right?

Is there anything bad about the cast iron B20 combo intake (the one with carb mounts)? How does the cast arn one run in the summer: if timing/mixture is correct will it still run hot and promote vaporlock more often (with the carb heat shields installed), or is this just junkman logic? Was there some issue with an intake balancing baffle. . . .? Curious. . . how many versions of the cast iron combo manifolds were used on the B20 . . . which years are considered best (if any)?

Gotta choose soon. . . . advice?