Cruising at 25-40mph Wideband is showing 12-12.6. Is there any benefits to going leaner. Where do you set your mixture? Engine is sbc 377cid, iron heads 380hp 430lbft at dyno with dyno headers, now with glm exhaust manifolds.

What rpm and vacuum are you at?

2200-3500rpm. Dont have vacuum cauge.

I run 12.8-13.2 in that range. Seat of the pants you likely won't notice anything. At 2000-2600 coming on plane I'm closer to 12.0 then it progresses to 12.8-13.2 around cruise at 2800-3200 rpm. It will use a little less fuel obviously but I don't think you'd be able to measure that amount unless you did a distance vs fuel test.

I've run AFRs in the 13.5 to 14.0 range during 3000 rpm cruise without knock or damage. HOWEVER, this was for test and eval only and I would not recommend doing so full time.

Thanks Trash, have to do some Wot testing before any tuning. Do you monitor both cylinder groups or only one? My sensor is now in group 2. I have Edellbrock air-gap with rochester q-jet.

One bank (2/4/6/8 side) but I have an MPI motor with flow balanced injectors. This is on a standard bore 377 stroker SBC.

I have a double fuel bowl Quickfuel 750 that's a lot like a Holley. I have just increased my jet size by 2 on my primaries for the same reason.
I was getting 13.8 to 14.1 in the 2850 to 3200 rpm range. Once I get on it, the secondary fuel fattens it up nicely.
I'm glad to see some justification for increasing the midrange fuel ratio.

See how lean my Marine 750 is compared to your quadrajet. It's a lot closer than mine is. The 12 to 12.6 AFR shows how well the Qjet works. It uses vacuum to determine fueling. If you want to change the midrange you can do that with a change to the metering rods, springs and/or jets. A stronger spring will lift the rods more for a given vacuum value. Or a narrower rod will flow more fuel, or a bigger jet will increase fuel too.

I am a q-jet guy. Newer had any issues with them. Going to use one in my 502 engine also, throttle shafts bushed and throats cleaned.