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Discussion Starter · #1 ·
I just finished rebuilding my engine. It only took me a year to finish this task with the help of some unscrupulous mechanics that did more harm than help. I have the original 1969 block with GT40 heads, roller rockers, nostalgia comp cam. performer rpm intake manifold, and 600cfm edelbrock carb. I´m using a mallory hyfire IVC ignition box, pertronix coil, and duraspark distributor. The problem comes under two circumstances:
1. When I first step on the gas to get going, there is a hesitation, a loss of power, and then when I press harder on the gas, the engine picks up strong.
2. When I´m cruising along at a steady speed, the engine starts jumping and stalling until I give it more gas. While I´m accelerating or release the gas pedal completely there is no problem, but as soon as I press the gas just enough to keep a constant speed starts jumping like crazy.

Anybody has ever had this happened to him. I´m going crazy and don´t know where to start checking. Any advice is welcome.
 

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Sounds like you have problems in the carb. Either Float level, power valve, or Accelarator pump. That would be where I first checked.
 

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Sounds like the engine is lean. You could possibly have a vacuum leak (check all your hoses and make sure all unused ports are plugged.) It sounds like a vacuum leak to me.

I'm not an expert on the Edelbrocks, but if it's not a vacuum leak, you'll need to richen up the carbuerator. I'm sure there are some guys here that can help you tune it.
 

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Discussion Starter · #4 ·
Thanks guys. I forgot to mention that the car idles just fine a little below 1.000 rpm, and when you punch the gas in neutral, it sounds great, no hesitation or anything. I´ll check for vacum leaks, if I can´t solve the problem this way, I´ll try with the power valve. I already check the accelerator pump and the floats, and they seem to work just fine.
 

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Discussion Starter · #6 ·
Well hell, I guess I better start reading that edelbrock carb article in Mustangs and Fords.
 

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The jumping around while you're cruising is probably from the carb being too lean like someone else said, usually feels like the car is surging a little.
The hesitation from a stop or when you punch it can be a couple things, either it's not getting enough of a shot of gas (accelerator pump on a holley) OR it's getting too much gas from the acc. pump and bogs cause it's too rich. Have someone watch the tailpipes when you get on it in gear and see if theres black smoke from too much gas, at least that'll narrow it down.
Check your plugs too after cruising around and not getting on it, if they're bone white it's too lean. They should be a little tan.
 

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I have the same carb and my car behaved the same way when it was tuned too lean. What rod & jet combination do you have in there right now? Go back to the Edelbrock factory calibration if it isn't already, and start modifying from that point.
 

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Discussion Starter · #9 ·
Thanks for your answers. My carb is stock, but I´ll check the vaccum and the lean condition and I´ll report back. Thanks again guys.
 

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...I would guess lean condition also.

I has similar symptoms, changed to Holley 650DP, let´s see when winter evades..
 

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The accelerator pump shot is really easy to adjust on the Edelbrocks, just move the pump rod to a different hole on the lever to get a bigger or smaller shot of fuel. From my experience, I had to have mine on the biggest shot (hole closest to the pivot point) in order to get rid of my off-the-line hesitation. If it's already on the closest hole, try putting it on the middle hole just to see if it has any affect. If you can't fix the hesitation with the accelerator pump adjustment, the next thing to try is a stronger power-piston spring. This will make it stage in rich sooner, but be careful because too heavy of a spring and it will stage in rich while you are cruising or under light load, which you don't want. And as far as the surging while cruising, like everyone else said check for vacuum leaks, and also you'll probably need to go with either a little larger primary jet or a metering rod that has smaller numbers (smaller diameter) to richen up the mixture some. In picking out metering rods, you'll notice they have two numbers... for example 73/47. The 73 is the diameter of the rod during lean/cruising mode, and the 47 is the diameter of the tip when it transitions to rich/power mode. So if you are having a cruise problem, but part throttle acceleration is good and clean, you'll want to find a rod that has a different big number and the same small number, like 70/47 to go 3 steps richer in cruise mode and keep the power mode the same. Make sense?
 
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