340 sputter on initial acceleration

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Jake lagrange

Jake lagrange

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My dart runs great, so it seems fires right up hold idle by her self after only a few seconds (no choke), sometimes when it's not fully warm yet and I go to accelerate not even hard it will go fine for maybe 2-3 seconds than sputter stumble than pick right back up where it left off, even on gentle accelerations. I was thinking my carb I didn't personally put it on came with the car I think it's a Holley 600 or 650. Any advice where to start?
 
Jake lagrange said:
My dart runs great, so it seems fires right up hold idle by her self after only a few seconds (no choke), sometimes when it's not fully warm yet and I go to accelerate not even hard it will go fine for maybe 2-3 seconds than sputter stumble than pick right back up where it left off, even on gentle accelerations. I was thinking my carb I didn't personally put it on came with the car I think it's a Holley 600 or 650. Any advice where to start?
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Sounds like an accelerator pump. 65'
 
pump shot (just watch it work, should be nice long steam) and check distributor advance plate movement, lube it.
 
Primary jets, if it was pump shot it would stumble as soon as you touched the peddle. Go up 2 sizes and see what happens ...
 
On the carb? Would that be something a tune could fix? A good cleaning? I don't know
How to make them bigger. Isn't holly the one with smaller primary jets compared to
Secondary
 
Buy a Holley book, study it ! ... yes the primary are smaller than the secondary jets. On my 340 I'm running an AED 750dp with 72/77 jets... no stumble whatsoever ....
 
Jake lagrange said:
After it's warmed up no
Stutter or stumble
At
Click to expand...

It's perfectly normal. Don't F up a good thing. It's not fuel injected. It will never run great when cold. Don't try to make it do something it cannot. You will only make it run worse. Don't look a gift horse in the mouth. There's nothin wrong with it.
 
Cold the raw fuel condenses on the floor of the intake and runs down the runner playing havoc with the AFR. It's not broken, just different.
 
Jake lagrange said:
only reason I asked my first dart never did that. Even just fired up
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The first one was probably running too rich. That will mask a cold startup. This one actually sounds like it's tuned about right. Stumbles when cold and runs well when warm. Normal.
 
Condensing fuel or just a cold combustion chamber, not being able to properly fire a cool intake mix that is otherwise the right mixture. EFI can be used to compensate; the computer uses human observation to incorporate corrections but the only equivalent on a carb is a choke.... which you don't have. The idle may be rich too, since it fires off OK without a choke..or you are good at using the accelerator pump to compensate!

A hotter spark MIGHT be able to fire off this cool mixture better... but maybe not. What do you have for an ignition system?
 
An HEI might really do you some good. It will provide much more spark energy and that starts a better kernal (initial spark) with a better burn.

Make sure that you points gap is set right. Being closed up a bit (which they will do with normal wear) can produce similar symptoms. Ditto for many worn/used ignition parts. Just replacing rhe PO's wrong ballast with a correct OEM ballast resistor on my '62 all original /6 points system made it fire better when cold.
 
You should hook up a choke. That's what they're made for. If you set your carb up right, it can run almost like fi. RRR is right on.
 
The carb on it has an electric choke, unfortunately not hooked up and I've knuckle deep in the brakes so haven't had time to figure out how to hook
It up, honestly I kind of want to hook the old pull choke.
 
Jake lagrange said:
The carb on it has an electric choke, unfortunately not hooked up and I've knuckle deep in the brakes so haven't had time to figure out how to hook
It up, honestly I kind of want to hook the old pull choke.
Click to expand...

Nothin wrong with a manual choke. Just give it time to warm up until you can hook the choke up. it will be fine.
 
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