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Carburetor tuning please HELP

78cordoba

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Hey guys I have a new Edelbrock 1407 and the idle mixture screws have no effect. im guessing i just need to tune the carb but dont know where to start any help would be very appreciated here are my cam specs

COMP CAMS CL21-671-4

Cam Style:Hydraulic flat tappet

Basic Operating RPM Range:2,300-6,300

Intake Duration at 050 inch Lift:239

Exhaust Duration at 050 inch Lift:246

Duration at 050 inch Lift:239 int./246 exh.

Advertised Intake Duration:284

Advertised Exhaust Duration:291

Advertised Duration:284 int./291 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.484 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio:0.484 in.

Valve Lift with Factory Rocker Arm Ratio:0.484 int./0.484 exh.

Lobe Separation (degrees):108

Camshaft Gear Attachment:1-bolt

Grind Number:pP284H

Computer-Controlled Compatible:No

Lifters Included:Yes

Lifter Style:Hydraulic flat tappet

Valve Springs Included:No

Retainers Included:No

Locks Included:No

Valve Stem Seals Included:No

Timing Chain and Gears Included:No

Assembly Lubricant Included:Yes

Pushrods Included:No

Rocker Arms Included:No

Gaskets Included:No

Valve Springs Required:Yes

Quantity:Sold as a kit.

In-Store Pickup:Choose In-store pick-up (OH, NV, GA, TX) on our web site.

Famous factory camshafts of the past are combined with the latest advanced camshaft technology to give you the sound and excitement of the musclecar era. COMP Cams Nostalgia Plus cam and lifter kits are specifically designed to capture the essence of the original '60s musclecar with additional power that you can feel in the seat of your pants. The new technology creates awesome response to give new life to any hot rod.
 
Look down the carb while it is running. It must be getting fuel from somewhere else if you can’t shut it down with the mixture screws.
 
Pretty big duration cam for a 7:1 400. probably have the idle cranked up so it will run.
 
A good way to tune an engine is to tune the distributor/timing before the carb.

What is the initial/total timing set at?
 
Usually the throttle blades are too far open into the transition slot of the carb for the idle screws to make a difference.
Start with initial timing which should increase the idle speed, then you can back off the idle speed adjustment and maybe get back on the idle circuit.
Not sure on the carter, but on a holley there is a set screw for the closed position of the rear throttle blades, and it can be opened a little bit, and the the front can be closed down a bit. Finally, you could drill holes in the throttle blades to allow more air in with the throttle blades closed even more.
 
Pretty big duration cam for a 7:1 400. probably have the idle cranked up so it will run.
Thats what Iv been told. I had a poor engine builder and have had to redo alot. such as the timing gears were off a few teeth at one point but that has since been fixed. do you think i need to go with a different cam? i was hoping i could make this one work. yeah id say its turned up some i dont have a tac and im having issues getting the timing just right probably do to the idle being turned up im still pretty new at all this
 
That is alot of duration cam unless you have a 3,500+ stall converter.
The distributor should be re-curved so you can add a bunch of initial timing (likely 16+ degrees at idle), and around 36 degrees mechanical advance at 3,000 RPM (vacuum advance disconnected when checking the timing.)
It concerns me that the cam was "a few teeth off". Hopefully fixed before installing the valve train. That is a good way to smash the valves into the piston, but those pistons are also like 0.120" below the deck at TDC, so hope nothing was damaged.
 
That is alot of duration cam unless you have a 3,500+ stall converter.
The distributor should be re-curved so you can add a bunch of initial timing (likely 16+ degrees at idle), and around 36 degrees mechanical advance at 3,000 RPM (vacuum advance disconnected when checking the timing.)
It concerns me that the cam was "a few teeth off". Hopefully fixed before installing the valve train. That is a good way to smash the valves into the piston, but those pistons are also like 0.120" below the deck at TDC, so hope nothing was damaged.
its not the original engine it has pistons that go all the way to the top with valve relief the all i know is it was bought at a swap meet not sure what was all put in it other than the cam. if thats the case im not looking for something that crazy. mainly just want to cruise in some pokerruns with it. i may just put the stock cam back in
 
If your Edelbrock is new, take the air horn off and do the float calibration as described in the manual. I bought a new 1406 may years ago and did so just to be sure everything was right. I did the float calibration. The float calibration was way off right out of the box. They may calibrate em at the factory, but since they are un-supported, think they get bounced around in shipping and get of calibration by the time you install it. It was also my experience that my 1406 ran pig rich. I had to order the kit of rods and jets to lean it out.
 
My 1411 was so rich that my buddy could smell it when driving behind me. I leaned it down 2 steps in cruise and 1 in power mode.
 
IMO....
#10's thought about the cam is correct. Long duration cams typically need more throttle opening to provide a reasonably acceptable idle. This allows the off idle transition circuit to feed fuel, preventing or at least inhibiting the idle mixture screws from controlling the mixture. Usually, the idle mixture screws will have no effect. The tendency is to adjust the primary main metering jets down and or increasing the diameter of the primary metering rods cruise step (Carter-Edelbrock [Eddy]-Weber) or Holley main metering jets or idle feed restrictions. Most of the time, these changes will have little or no effect.
A possible fix is to drill small holes in the primary throttle plates, directly opposite the idle feed transition slots, to add additional air, allowing the throttle plates to close furthur, yielding a controllable idle mixture. Perhaps a good starting diameter for these throttle plate bleed holes is 0.125" diameter. The final dimension will have to be determined by trial and error.
Some OEM applications already use this "fix", like the center Holley on a six barrel engine.
BOB RENTON
 
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Thanks everyone for the help, but I believe I'm going to back to the stock cam and work on upgrading my rear end before i get a cam again if anyone is interested in this cam I'm willing to part with it. Just let me know
 
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