Alan,
Although I've seen many written statements in vintage magazine articles from the SD 455 era, I too have not seen a PMD statement concerning the drive by noise levels. I can only speculate that the magazine editors got this information from someone at PMD rather than from their own assumptions.
I've also wondered why the '74 GTO used the only funtional shaker hood scoop in the Pontiac line that year. Again, I'm only guessing, but with the smaller mild-mannered 350 engine, it may have been less of an issue than on the bigger more agressive Trans Am engines. You would surely think that Pontiac would have wanted the functional scoop on it's premier performance engine if it was at all possible.
As for the Formula hood scoops, I'm thinking that because they had longer passages and they weren't as open to the outside air as the shaker hood scoop was, they may have been less noisey. The Formula scoops had some baffling in them to keep water out of the carb and this probably muffled the sound a bit, also. We can only guess until we hear from someone on the inside.
I can't give an answer as to why Pontiac was going to make cold air induction a required option on the SD 455 A-bobies and not be available elsewhere in the line. It's hard to base anything on the information that we have available to us. Who knows if the the planners at PMD were scambling so hard at that time to just get the Super Duty package out the door that a lot of the documentation became a little vague. They were up against a lot of resistance at the time. All we can do is brainstorm to find as many answers as we can to the many questions out there about this great engine.
Jim
|