tuning a 401 w/ 1406 Edelbrock

[Pepe401]

I've got a 401 with edelbrock intake, carb(1406), and headers. I'm having difficulty getting rid of a lag/pause. When going from a stop using part throttle the engine starts to rev up then stops briefly and then picks up again. I have moved the pump position to maximum fuel dump, tried changing step-up springs, jets, and rods but have not found the right combo yet. Does anyone else have this combo or something similar? If so what jets, rods, step-springs are you using? Any other suggestions would help.

[Ralph]

It sounds like you're getting to know the carb pretty well. It's not uncommon for the accelerator pump to be bad, in which case changing hole positions doesn't fix the lag problem. With everything else you've tried, my recommendation would've been to replace the accelerator pump first.

[rhamby]

I installed a 1406 recently on my 360 and had a great experience with Edelbrock's Tech. Support folks. They provided jet rec. and tuning methodology which really helped.

1-800-416-8628 or
edelbrock@edelbrock.com

[<Tom 400 CFI>]

TTT

[joe]

<BLOCKQUOTE>quote:</font><HR>Originally posted by &lt;Tom 400 CFI&gt;:
TTT<HR></BLOCKQUOTE>

Great Googley MoogleyGreat Googley MoogleyGreat Googley Moogley?

[<Tom 400 CFI>]

Great Googley MoogleyGreat Googley MoogleyGreat Googley Moogley Right back at you little joe! :rolleyes:

TTT = To The Top. I wanted to see more responses, because I don't believe anyone has hit the problem. It is not the accelerator pump. The pump shoot's a good healthy shot. Plus, there is NO hesitation from Idle to instant full throttle.

I've been helping "Pepe" out, and I'm rather at a loss for ideas here, and I was simply trying to stimulate some more brain storming. Is that O.K. Joe?

[joe]

Oh cool...an unregisterd guy with an attitude that speaks in abbreviations...this could get good :D

[Snakeyes_Tx]

Awe c'mon Joe, I've been known to do a BTT (Back to top) every once in a while too...

I was stuck on the AFAIK for a long time till someone cleared it up for me.

[Tom 400 CFI]

Brad, next time you have the carb apart, check the transfer or "off idle" circuits to make sure they are not clogged. Is there an adjustment for these on your carb? This circuit is responsible for fueling the engine as the throttle plates leave the orfice for the idle circuit discharge. It is designed to "cover" the area between the Idle circuit and the main. It seems like that is where your trouble really is.

"When going from a stop using part throttle the engine starts to rev up then stops briefly and then picks up again"

It starts to rev up because of the accel pump. But then after the shot is burned it is like what ever was supposed to kick in, isn't there, after another second, the main system is finally discharging fuel, and off you go. Just some more food for thought.

;)

[JOECOOL]

Try moving the pump rod outward. You may actually have too much pump shot and its flooding sort of.
Also double check your float level. As well as you pump rod hight. Real important as the pump uses a notch on the pump wall instead of a check ball like the older AFBs. Is the pump cup fit nice and tight on the housing walls? If its loose it is bad. FYI i had a bad NEW accel pump plunger when I rebuilt my Carter AFB.
Second what is the condition of your Distributor? Rotor and cap?
Is your EGR hooked up? If yes try runninmg without it and see if it helps.

[ October 03, 2001: Message edited by: JOECOOL ]

[Lindel]

Check and double check the ignition timing, my 360, with the Edelbrock intake/carb (2131/1406) is very sensitive to timing, now. Once you hit the sweet spot, you'll know it.

Your lag will go away, and the power output will come way up.

I've found that for the most part, the stock carb, with the accel pump at the bottom hole (for the largest shot), with the rest stock, works very well. Good power, mileage unchanged from the 2150.

[Pepe401]

Thanks for all the input everyone. I have experimented with diffrent jets, rods,step-up springs, adjusted the timing to 12degrees advanced, adjusted float level, inspected accelerator pump thoroughly and undoubtedly it does run better as a result but it still has that lag/hesitation at part throttle. My guess at this point is it is definitely a fuel delivery issue.
I still need to check the transfer circuts if they do exist on my carb.
I have not changed rotor and cap recently and it is a good idea however the problem of the hesitation does not happen when it's floored.
It is as if the accelerator pump just doesn't have enough throw at partial throttle to give the 401 what it needs.
I'll keep playing and let you know what happens.