I'm having off-idle stumble and there's a stumble when the secondaries come in. Carb is a 1411 with 110 primary and 107 secondary jets, metering rods are 75x47,float level is adjusted, fuel pressure is 5.5 and timing is 36 @ 3000. Engine is a 440 with 1.6 exhaust valve,torker intake,headers and a mild cam, 727 with 3000 stall and 3.55 gears. I tried all three pump linkage holes and nothing changed, I think. Should I start jetting it down or up? try a larger squirter than stock 35?
Are you getting a proper accelerator pump discharge with what you have? A strong squirt in each primary bore. Eddy makes a pump nozzle kit that has a 43 nozzle. Or you can drill yours, small steps. The pump seal could be getting tired or dirt in the check valve. The secondaries are mechanical on the Performer carb with a weighted air valve in the secondary bores that opens as demand develops. I would make sure you carb is clean. The current gas seams to love to varnish up the small passages in our carb.
Yes, accelerator pump works and squirts fuel like it should.Just changed the fuel filter and the carb is clean. I have the 1489 calibration kit and have tried different jets,metering rods and springs.Hesitation is still there.Right now I disconnected the secondary rod to eliminate the primary stumble first.What would be right size jets for a 440? Minimum to maximum? If the bigger nozzle does not eliminate the stumble, then I'm gonna have to sell it, I guess. :shruggy:
Edelbrock has a carb manual on there website. Your jetting and rods are what is stock according to the manual.
Define hesitation, Are you taking about a stumble on a normal acceleration from a traffic light?
You said it hesitates again as the secondarys open? Are you depressing the gas petal to the "lump" and then flooring it ?
The secondarys open as fast as you can press the petal down . There is an air valve in the secondary bores that is weighted closed and opens as the engine demands more air. Edelbrock uses a transition circuit to smooth the transitioning to full secondary air flow. This has a similar effect to Holleys with vacuum secondarys.
I have an 800 Performer If you snap the throttle wide open on a cold day it will some times gasp for a fraction off a second. I have put the largest noozle (43) in and streched the accelerator pump spring to make it discharge faster, both helped.
I have heard about carbs that where idling with a lot of the throttle transfer slots showing,hesitating off idle.
I dislike the AFB-based carbs because of the common off-idle stumble, my thinking is that the pump is lazy at slight throttle tip-in compared to others...enriching the idle often helps.
WOT bog can be helped by increasing the secondary jet size.
Thanks flyinlow and John_Kunkel! I unhooked the accelerator pump rod just for kicks and same problem but much worse.So I'm hoping that the 43 nozzle will eliminate that.
I got the 1411 carb calibration kit so I only can change the main jet stock 110 to a 113 and secondary stock 107 to a 110. I think I should have get the 1407 carb calibration kit, it has bigger jets and smaller rods.
Off Idle Stumble or Surging often occurs when the mixture screws have not been set up correctly.
Quote from: Piston_Freddy on May 26, 2011, 05:48:19 PM
So I'm hoping that the 43 nozzle will eliminate that.
The nozzle size isn't the real problem, the problem is the design. With the engine off look down the primary bore as you slowly open the throttle and you'll see how much the throttle opens before the pump actually starts to squirt.
I'm selling the Edelbog and getting something that lets me put the pedal to the metal and lights up the tires without hesitating. Thanks for the help!
Holleys DP carbs come with two midgets with super-soakers that drench the venturi's with gas when you mash it. .........
The Holley does have a better accelerator pump.
Quote from: flyinlow on May 27, 2011, 05:14:22 PM
Holleys DP carbs come with two midgets with super-soakers that drench the venturi's with gas when you mash it. .........
Its true.