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Hello! I am the current owner of a 1979 Bronco it has the 351m with the c6 transmission, my truck was sitting for 10 years before I acquired it from my dad and begun restoration, before it sat it was equipped with a dual plane edelbrock intake, and an edelbrock 1406 carb, I've always had an issue with hot starting the engine, it would turn over 5-10 times before it would fire, in order to mitigate this I put a dead head fuel pressure regulator and a 1" spacer under the carb.

Now to get to the issue I have now, I have been tuning the carb for better mileage and better mid range torque, I've tuned it for way better mileage and for much easier hot starts, but I have run into an issue where the truck will not start when it has sat overnight, it will crank and crank until the batteries go flat, but if i stop cranking the engine will fire but it will fire in the wrong direction, it usually it will spin once or twice backward and will not start after. Even stranger when i recharge the batteries for a couple minutes it will start just like it usually does. Im still stumped on if the engine is flooding when cold, or the ignition system is failing in some way, im thinking either magnetic pickup or a bad/loose connection to the coil causing voltage drop when the starter engages.

Another few notes, once the truck starts in the morning it will start and run no problem all day, and my hot start issue is almost resolved, it only takes a rotation or two to restart the truck after it has been sitting for more than 15 minutes, the only two other things i can do to completely rid the problem is to get one of those aluminium heat shields or the wooden spacers edelbrock sells.
 

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Not to be a wiseguy, but do you think all this screwing around got you anything compared to the stock setup? I dont think the cyl heads/cam on a 351 can even make use of any extra fuel you throw at them. They are so choked off.

That said, have you tried a shot of starting fluid when you cold start it? This would confirm a lean condition on the choke. Also, as sort of a poor man's choke, does the carb have an accelerator pump? Actuate the linkage a few times to put a shot of gas in the throat and try to cold start. I think it would be wise to determine if it is a lean condition or if you are loading it up and flooding it.

The first place I would look is the choke circuit on the carb. Is the choke vaccuum operated? Is it working properly?
 

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Is your cold cranking speed the same as your hot cranking speed?

Like @para said, choke and accelerator pump is key to getting it started. I occasionally have to give mine two pumps of gas if it has sat for a bit. High idle cam also comes into play. The 1406 choke uses manifold vacuum to operate the choke piston against a spring force that decreases as a function of spring heat up.
 

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1984, 300 L6, smogless, manual 3speed with overdrive.
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Is your timing set properly? And see above.
 

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I have a story that might help: Our 1969 ford Falcon Futura wagon.... 302 engine... could be tough to start. Long story short: the starter solenoid relay under the hood was bad...... not dead bad, just bad, where the starter would not get a strong 12V shot. I am guessing that the internal contacts were burned. New one makes it turn over really strong.
 
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