That sparking business I have never seen before!
I skimmed the thread from the beginning and did not see anyone mention that both the carb and the tank have to be vented.
Neither the pump nor the carb actually suck fuel. It is the 14.7 psi of atmospheric pressure that enters the tank thru the vent, then pushes the fuel to the front, in response to the pump creating a tiny low pressure area inside of it. Once there, the pump pushes it up to the float bowls. From there, it is the low-pressure inside the chambers on the intake stroke, that prompts the atmosphere to push fuel up and over the idle/main wells.
If your float level is too high, it becomes too easy for the atmosphere to push the fuel over. If too low, then too difficult.
Gasoline is made up of many different molecules, the lightest of which boils at about 95*F. If it is boiling in the bowls, then it is also boiling in the wells. With the engine running, this is no big deal because the bowls and the wells are vented, so it just escapes back into the atmosphere. And your engine does not need or want that crap that is boiling anyway; it is only in there to help your car start/run when the engine is cold. As the switch-over to EFI is happening, eventually I suspect, the formulators will phase that constituent out completely.
Up here in Manitoba, we don't have your high-heat problems. But we do have a significant base elevation that ranges from about 1100 ft just West of me, down to 800 ft about 30/40 miles East of me. I am at 930 ft. Elevation changes the boiling points of all the molecules. And we have daily temperature swings of 40 to 60 degrees F .. So I need that lightweight skunk-pizz.
This is another reason I have a mechanical fan...... it turns continuously...... continuously blowing on my aluminum heads, my aluminum intake, and my aluminum bodied carb; continuously cooling those, and then continuously pushing the hot air down and out to underneath the car.. Yaknow; I don't care how much power my T-clutched,7-blade, large-diameter, all-steel fan, sucks; I will never ever install an electric system.
Now, consider this; where is your carburetor vent?
On a Holley it is in the airhorn with a standpipe, inside the air filter house, semi-protected from the underhood air dynamics.
But on a Carter-type carb,the last time I looked it was on the top of the bowl with a mechanical lifter arm, synchronized to throttle movement, OR it was terminated in the charcoal canister. What happens when my factory 7-blade starts pushing hot air across the vent hole? I mean IDK, and I don't want to know, which is just one of the reasons I don't run that type of carb. The bowl HAS to have access to a constant atmospheric pressure.
Overnight, those lightweight VOCs evaporate, leaving you with the heavy stuff to try an ignite in the morning. The boiling points of those remaining vary all over the place, with the heaviest not boiling until 450*F, IIRC. So then lighting that syrup with a cold plenum, cold runners, and cold chambers gets a lil more difficult. And your Idle-timing is way retarded, so even if whatever gets lit, a lot of it is gonna go straight thru the system, and out the tailpipes,.... until the metals warm up some. And because of the retarded timing, the engine has very little idle-power either, until it warms up.
But, you say, your idle-timing is NOT retarded.
Oh yeah?
Next time your engine is cold, in the morning; immediately after it fires up, just start cranking in some timing, until the engine rpm stops increasing. Now read the timing. What you see there is the correct amount of idle-timing for whatever the rpm rose up to. I'll guess you will see hi 30s to mid 40s. So even if your idle-timing is set to 18*, it is less than half of what the cold engine wants. And so, that is where the lightweight VOCs come in handy.
Put a scanner on your EFI car, and see how it is programmed....
In any case, I really just wanted make sure the vent was not overlooked. Good luck!
As for me; I keep a 500cc bottle of fresh fuel under the hood, into which I have mixed stabilizer and 5% two-cycle oil for ring sealing and lube. I have installed the air filter house on top of the hood and sealed the underside of the hood to the top of the carb. So when I open the hood, shazzam there is my airhorn staring back at me. I squirt some gas in there, close the hood, jump in and twist the key; and instantly it fires up. Immediately, I dial in some advance with my dial-back timing box, back out of my carport and idle out thru the neighborhood. About three/four miles later,on the hiway now,the car surges forward about 3 to 5 miles an hour, indicating to me, that the engine is ready. I retard the timing back to normal, and it's go time!
