To further answer your question, the dual idler gear drives are for people who want to brag about "I got a gear drive, man" at the cruise ins. They're absolutely worthless as far as keeping accurate cam timing, because the dual idler set can rock back and forth several degrees before the crank ever moves the cam. The single fixed idler removes all of that play. If you look at the price differences between the two, you'll see the prices reflect that. Look at the Milodon single idler setup for the small or big block. They ain't cheap. That's because they're very accurate. I basically turned this dual idler set into a set similar to a Milodon set.
