OK carburetor experts.

My 83 F150 5.8l/351W has been treated to an Edelbrock Performer manifold and a 1406 carburetor running "out of the box" calibration. Also running Hooker long tube headers, dual 2 1/2" exhaust, no X or H pipe, glasspacks and a stock cam.

It runs reasonably well. I have been playing with the choke adjustment to the point that I'm satisfied and I have set idle mixture screws just out from the point where RPM starts to drop. Idle quality is good. Timing is set to stock spec and I have a factory non-catalyst truck, (no AIR or cats).

There are a few flaws in this system that I would like to iron out. Cold starts are acceptable. Choke sets up and pulls off correctly. (electric choke). Hot starts require full throttle after sitting a short while. I believe this is fuel percolation. I may try to solve this with an insulating spacer. There is an intermittent stumble with off idle acceleration, but it pulls hard once it "catches". It also has a burble at cruising speed.

I'm not expecting EFI like smoothness and power, but I've had carbureted vehicles in the past and I think it should run a little smoother.

Any suggestions?

 

The burble at cruising speed can be lessened or eliminated with the metering rod spring kit. Try the 3" blue springs. Had the same deal with mine and the 3" blue springs eliminated it. As far as perculating, mine did the same thing. So does the aluminum Summit/Holley carb even with a phenolic spacer. The phenolic spacer did help a little bit though. It's just the ways of the fuel these days. Not a whole lot can be done about it. As far as the off idle acceleration stumble, Change the accelerator pump arm from the stock middle hole to the top hole, which should lessen the pump shot a little. Mine ran best this way. But, no two engines are the same.

Hopefully I remembered most of that stuff decently and didn't make my self look like a babbling fool.

 

The Eddys do have a tendency to start slowly when hot. The insulator may solve that.

On the off-idle stumble, I would have suggested going the other way from what Matthew said, but he may be right and you'll know soon enough. If it is worse go the other way.

On the burble at cruise, we need more info. The springs Matthew referenced only come into play in low vacuum conditions, like down around 5", and that takes a fair bit of throttle to create. So, is your burble just cruising, and at what speed/throttle setting? You could be on the lean limit and need to change out the metering rods, but let's discuss first as you will probably also need to change the jets.

 

Thanks Matthew and Gary. Going to try the suggestions.

Little under the weather today, but I'll get a little more info on it. Tailpipes are black and sooty, so I'm thinking it's running rich. Problem is it's been mainly short trips around town at low speeds all winter. Really got to get it out on the highway and that is where the burble comes in. Typically cruising 60 to 65 mph in high gear, light throttle.

I'll put a few highway miles on it and check the plugs.

 

If the burble is running steady then the springs won't make any difference since any spring will be overcome by the 10+ inches of vacuum. In that case you'll need to change rods.