The Stovebolt Site Forums The Shop Area Engine Shop rochester b off idle tuning

At 7000 feet and 16" vacuum at idle, it tells me your vacuum gauge might be reading a bit high. That's more along the lines of what I'd expect at 2500~3000 feet, but still it is very encouraging. It suggests you're not losing much vacuum inside the Rochester. Yes, definitely...if the PP is opening around 5, then the removal of 4 coils would be the answer. Of those springs I found, one of them was notably weaker and a couple were pretty strong. I wondered about this but the other Jon told me he thought Rochester had used something like 7 or 8 different springs and any time these went through a "rebuilder's" hands, any sort of mixing and matching of parts would happen. The leanest AFR between 5 and 10" vacuum says your power piston is off the valve (a very good thing and not something I'd be inclined to change). 16.5 to 17.5 is slightly on the lean side, but probably not worrisome. A slightly larger main jet should bring that back to 15 or so (where I'd be a bit more comfortable). You don't want it too lean, but you also need to know your AFR (particularly the sensor) could be giving questionable readings unless it is brand new. Oh, and you probably know this, but don't leave the AFR sensor in the exhaust pipe if the gauge isn't being used. Even a little bit will mess them up. And those are sensitive things. They need to be positioned and angled just so to get the right readings and most of them want to be something like 24" from the junction of exhaust pipe and manifold. But it sounds like yours is pretty close to right. As for leaning out at WOT, that isn't surprising to me. With that 53 jet and the throttle wide open, your fuel is limited but your air intake has been increased, so as I see it, you reached a max with the jet somewhere before WOT and now you're just catching up with air to fuel.