Carb recommendtion

I would love some advice on where to go with this carb. It is a 71 351C 4V in the orginal car, a 71 Mach 1. The previous owner installed a cam, edlebrock high rise, Weber 750 CFM vacum secondary carb and headers. The care came with the "Drag Pack" and factory 4 spd with "Hurst Shifter". The engine loads up with fuel real bad when it idles for over 3 mins.(a long red light) The carb needs work as the engine sputters at high RPM and, it is hard starting after it sits for more than a week. I drive the car a couple of times a month and I love the "gobs of torque" this thing has but I wonder if this is the best set up for this car. Here are my cam specs

Speed-Pro Cam
Intake valve lift .503 Duration 308 Lash HYD
Exhaust valve lift .507 Duration 314 Lash HYD
Rocker Ratio 1.73-1
Distance between lobe centers 108 degrees.

Carb
Weber 750 vacum secondary

Intake
Edlebrock Highrise (medium rise, I don't know the detail.)

Soon to have "Doug's" ceramic coated headers.

Question

Is this a good set up for this car?
I have a brand new Autolite 4300 original 4 barrel for this car, would this be a better carb on this intake and cam conbo?
How much difference in performance would occur if I put the original intake and carb on this config?

Any help would be appreciated.

It sounds like you may have the wrong power valve in it. Have you checked to see what kind of vacuum you are pulling?

I haven't, but I will. What power valve would you recommend?

Before opening anything up, try a few simple things first.

The fuel bowl levels need to be checked. The best way to do that is run the car, warm it up. Shut it off. Unscrew the fuel bowl sites on the front and back, and when you open it, just a little gas should seep out. If none does, try bumping the side of the car a little and see if the fuel spills out.

If a lot comes out, that maybe your problem right there. If you have an aftermarket fuel pump, that could also be an issue, as you maybe making too much fuel pressure.

Lets us know what happens.

Power valve should be about 1/2 what the idle vacuum is.
if you car idles with 11 inches of mercury then your power valve should be opening at 5.5 inches. Holley power valves are stamped with the opening vacuum.

Originally Posted by Fordz

I would love some advice on where to go with this carb. It is a 71 351C 4V in the orginal car, a 71 Mach 1. The previous owner installed a cam, edlebrock high rise, Weber 750 CFM vacum secondary carb and headers. The care came with the "Drag Pack" and factory 4 spd with "Hurst Shifter". The engine loads up with fuel real bad when it idles for over 3 mins.(a long red light) The carb needs work as the engine sputters at high RPM and, it is hard starting after it sits for more than a week. I drive the car a couple of times a month and I love the "gobs of torque" this thing has but I wonder if this is the best set up for this car. Here are my cam specs

Speed-Pro Cam
Intake valve lift .503 Duration 308 Lash HYD
Exhaust valve lift .507 Duration 314 Lash HYD
Rocker Ratio 1.73-1
Distance between lobe centers 108 degrees.

Carb
Weber 750 vacum secondary

Intake
Edlebrock Highrise (medium rise, I don't know the detail.)

Soon to have "Doug's" ceramic coated headers.

Question

Is this a good set up for this car?
I have a brand new Autolite 4300 original 4 barrel for this car, would this be a better carb on this intake and cam conbo?
How much difference in performance would occur if I put the original intake and carb on this config?

Any help would be appreciated.

Being this car is a 4 speed have you thought about a double pumper? They make great out of the gate throttle reponse. They like gas but kick as if tuned properly. Depending on you gear ratio and which toploader you have, 2.32 or 2.78, a dbl pumper in the 700 cfm to 750cfm range should work out of the box. My 2 cents.

You know, I've been told that a 351C can't handle anything larger than a 650 CFM carb. The car now has a 750 vacum secondary Weber, and it really loads up when it idles for anything over 3 mins. With that said, I went on the Holley site, punched in my data, and it spit out a recommendation of a 750 vacum secondary. So I felt pretty good about it. I am still not convinced that I have the best choice, so my question, what would the 750 double pumper add to this package that the current carb doesn't? Thanks.

IMO

You need to source a HOLLEY tech manual and go through the carb to find out why it is idling too rich.

people also told me not tput anything bigger on my 302 than a 600. I took advice of people here and put on a 650 DP. It runs incredibly well and makes significantly more power than the old 600 that was on it. Your car could pobibly use a 700-750 DP if you rev it high. Seeing that you have a 750 already, you should tune it up, get the floats right,he righ power-valve, those kinds of things that have been reccomended.

Can you verify which carb you have? I havent seen a 750 Weber, but I have seen 750 Holleys with Weber Power Plates.

Does the carb have a number on the air horn?