Idle Surge In Gear

Thanks Will. We have tried most of that. Do you have a phone # I could call you at? My email is jwitchdoctor@aol.com. Thanks

 

Hey Will,
Thanks for your input. I found this thread through a search of the same problem.
I was having a horrible in gear surge w/ a new SBC and 871 w/ bug catcher. I could barely concentrate w/ staging because of it. It was because I put the heaviest return springs that I could get on the blades. I thought I was doing it for safety to prevent them from ever sticking open. Anyway, I lightened them up and it idles perfectly at 2400 in gear.
problem solved, BUT, I can't wrap my head around, 1) Why putting it in gear starts the surge and
2) How can heavy springs be causing flex? Looks to me like they would keep the butterflies locked down and stable.
Just trying to understand the mechanics
Thanks