Stumbling 390-2V . . Any suggestons?

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cooleybrian@gmail.com - 15 Sep 2006 15:55 GMT

I have a '69 Galaxie with a 390-2V that hesitates when you first press
the accelerator pedal. After the stumble, it catches on a runs very
strong and smooth, so something is just wrong in the initial tip-in of
the accelerator.

I have a nearly new Pony Carbs rebuilt Autolite 2100 in there . . have
carfefully timed the car for a smooth fast idle and high vaccum. It
doesn't seem like a mixture or choke problem, and since the idle is
smooth I don't think it's a vaccum leak.

Does anyone have any ideas/experience in solving this?

Thanks.

Brian
San Francisco

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Big Al - 15 Sep 2006 16:02 GMT

> I have a '69 Galaxie with a 390-2V that hesitates when you first press
> the accelerator pedal. After the stumble, it catches on a runs very
[quoted text clipped - 12 lines]
> Brian
> San Francisco

First thing to check would be the accelerator pump. Do you know how?

Al

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cooleybrian@gmail.com - 17 Sep 2006 14:46 GMT

> First thing to check would be the accelerator pump. Do you know how?
>
> Al

No, not sure how to do that. Any tips?

Thanks.

B.C.

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Ol' Duffer - 15 Sep 2006 18:35 GMT

> I have a nearly new Pony Carbs rebuilt Autolite 2100 in there . . have
> carfefully timed the car for a smooth fast idle and high vaccum.

The method you describe will usually lead to excessive advance.
Use the timing marks on the harmonic balancer, get a strobe and
do it right. Once you have it timed, then you could think about
fiddling with the carb, but you apparently already have, so I don't
know where that leaves you.

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Tom Adkins - 16 Sep 2006 02:40 GMT

> I have a '69 Galaxie with a 390-2V that hesitates when you first press
> the accelerator pedal. After the stumble, it catches on a runs very
[quoted text clipped - 12 lines]
> Brian
> San Francisco

The Famous "wiggle the gas pedal Ford stumble". You ccan try richening the the
accelerator pump a bit. First, set the timing to spec and verify thet the vacuum
advance is working properly.

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Backyard Mechanic - 16 Sep 2006 02:41 GMT

> I have a '69 Galaxie with a 390-2V that hesitates when you first press
> the accelerator pedal. After the stumble, it catches on a runs very
[quoted text clipped - 5 lines]
> doesn't seem like a mixture or choke problem, and since the idle is
> smooth I don't think it's a vaccum leak.

Is there any 'popping' on decel? If so, too lean.

But, if that carb is the same as my 66 390 2V, I seem to recall the accel
pump is adjustable. Could be wrong

Signature

Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

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Tom Adkins - 16 Sep 2006 06:04 GMT

>>I have a '69 Galaxie with a 390-2V that hesitates when you first press
>>the accelerator pedal. After the stumble, it catches on a runs very
[quoted text clipped - 10 lines]
> But, if that carb is the same as my 66 390 2V, I seem to recall the accel
> pump is adjustable. Could be wrong

Nope, BY, you arent wrong, same carb. The lever on the throttle shaft is slotted for
fine adjustment. The accelerator pump arm on some was slotted for more coarse
adjustment. Smallblocks were pretty easy to adjust the pump stroke on because they
just rev so quickly. FE motors were touchy about accelerator pump, vacuum advance, and
initial timing settings because they reved up slower. Those engines would stumble on
acceleration if the moon wasn't in the right phase or the temperature wasn't just
right ;) This was a Ford thing on many engines through the 70s, but was most prevalent
on the FEs. It can be fixed with some diligent tuning, at least for a little while.
As a rule GM cars didn't suffer from this problem, but I remember some of the late
60s and early 70s HP and PI Ford motors that used the Rochester Quadrajet that still
had stumbling problems.
If you drive an old Ford with an FE motor, you learn how to wiggle your foot on
takeoff :) How much depends on your tuning ability.

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