Shelby Aluminum

[steelcomp]

Dave, you made some good observations and I'll try and shed some light where I can. I'm not as "versed" on GM's history and their design criteria, so I can't, without doing some research, speak to the purpose behind their BB design. The comments I made as far as the 385 being a "performance design" were of course made within the considerations of a production application.
There are, as KC stated earlier, few parts in a contemporary race motor, that can be related to the production engines. Most of the info I have been offering has been directed at factory design, and production performance, which, as KC also stated, was all we had twenty years ago. BUT... the outgrowth of what we have today came from those factory designs. The BBF offered many of the ideas that are still being built around today, and were copied by most of the other mfgr's.
I was just visiting some friends at Johnson Racing yesterday and was trying to get cought up with what's going on these days. In the world of drag racing, things are going crazy. IHRA is allowing these guys to build 800+ inch motors!! They have all gone to a 5" bore center. NHRA with their Pro Stock class is still limited to 500" and a 4.9" bore ctr. But it was interesting that the comments regarding changing bore centers were all based on (copying) the Ford 385 design.
The BBF was designed at a time where big cubic inches were becoming the vision, and HP was being found at higher rpm's. For that purpose, the BBC was limited. (Don't forget, in 64/65, 427" was a BIG engine) The BBC engine builders had a terrible time with the heads trying to get the different port designs (long/ short runner, left/ right turn...in the same head) delivering the same performance. They were a porting and tuning nightmare. We already touched on chamber design and valve angles.
The bore/ stroke issues are the same. Optimal is a relative term...the application has a lot to do with the design. The BBC has a very poor rod length to stroke ratio which is an important factor in general engine performance. This is a result of their compact design, but not in their favor as far as performance. Unfortunately there hasn't really been the kind of r&d done on the smaller cube 429 as there was on the 427 BBC, but even in that displacement, the BBF has the same advantages I have mentioned. Equally built, the BBF would have the advantage. The only disadvantage the BBF has in the smaller CI range, with the tall deck design, is intake runner length. The BBC has a much shorter runner length and this can result in more HP potential, (again, depending on application) but not in torque, although I think with today's intake technology, that isn't as much a problem. The 351W has the same problem. Ken Duttweiler did an experiment years ago with the best 351 parts he could get, and a comprable 350 SBC. He simply couldn't (at that time) get the HP out of the Windsor as he could the Chev, and he attributed it to intake runner length.
In any case, the larger the bore, the better the breathing potential, and the better the rod/stroke ratio, the better the dynamics, weather at 200ci or 800". The 800" motors give up the stroke/rod ratio over shear CI displacement, but make enough power to justify it.

Difference in designs has always been a Ford "problem" but once you learn about Fords, there's a lot more interchangeability than it seems. There's also a lot more combinations and options available with Fords, IMHO. (in my humble opinion) I think you hit the nail on the head when you said that "Ford just took Chevy's design and made it better, in some respects, depending on the (application). The BBC was (is) not a bad engine. It was a stepping stone in design ideas which inspired many new ideas.

Ahh, the Allison. An incredible engine! And the Cosworth. You're right, both designed for very specific purposes. Again, my input had been intended for "production" based designs that engineers had to take many different applications and expenses into consideration. "Purpose built" designs like these two works of art are far more specific, and can eliminate a lot of waste and "over design" resulting in a much more refined package, and better outcome. BTW...most of the undercut bolts were designed that way for a more consistant bolt stretch, as an engineering consideration, rather than save weight, but again, a testimant to the detail that can be given to such designs.