We figured this out. Positive discussion of a shared problem is fun and always fruitful. At the very least it helps us see where we are making mistakes (the big-beam idea). Often it leads to really cool stuff. If what we found in this discussion is correct then all of us (even the LS guys ) now have a cheap way to check our motors for resonance.
I agree about the “should work” principle. I’ve done it myself too many times. As soon as I get the inverted junkyard 305 smoking I’ll hook up our garage “torsiometer” and see what happens. It reminds me that I should have a crappy motor set up on a test stand at all times. It would be handy for testing all kinds of stuff.
If anybody is interested in discussing the 180-degree V8 crank idea maybe we could start a new thread? I’d like to talk about the mechanical advantages/disadvantages of fitting one to an otherwise stock V8.