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Trying to improve cold starts with a Demon 850

how much vacuum do you have at idle
gas and not driving the car that much could be the culprit for having bad gas
and gumming up the carb
barry grant would recommend rebuilding your carb once a year
 
5 times to the floor, then nurse it for about 5 minutes.
 
I replaced the primary metering block a couple years ago when I dropped the original and broke the white plastic vent extension. I've replaced the fuel bowl gaskets a few times but haven't had the carburetor fully apart.
Idle vacuum....Not a clue. When I had a bigger cam it would register a 4-6" number in gear at idle! The milder cam I have now more than doubled the vacuum numbers to something like 11-12" in gear and around 17 in neutral. I don't know what it is now. I have not checked it in years.
 
I had a thought.....
Can a battery be charged just enough to start the car but not provide the right amount of voltage to power up the ECU ?
I had an Optima that has struggled to hold a charge and I only recently learned that the top voltage it was reaching was below a target number.
Battery voltage chart.jpg


It was running in the 12.2 to 12.4 range at the very best. This chart shows that to between 60-78% charge.
To recap, once the engine was up to operating temperature, it ran great. Could it be that the cold starts taxed the battery enough that the alternator was not allowing enough power to operate the ignition?
Anyways.....
I texted with my carburetor guy. He found an electric choke kit in Utah.....The LAST kit in America so he says. Soon I'll have the Demon back and have the car running again.
 
Kern, yes, ethanol from pump-gas will leave a residue coating that will plug every orifice. You're going to need to take the carb off, clean it, and visual look it over.

Here is a picture from my EFI when fuel was left in it -
IMG-20191111-163252566-HDR-2.jpg


You shouldn't need an electric choke, but it may help.

Just my opinion with fleet vehicles, don't buy modern Optima's [made in Mexico]. We've replaced all of ours with Northstar batteries due to failure rates.
 
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ok so the California gas is about a year old? And the starting gets worse every month? heehee.
Pull a fuel sample out of the float bowl; it better be clear with no water in it.
Slightly yellow is a hard start but will run well enough to run around at Part Throttle.
Orange is really hard to light, but if you get her running, you can put her on the trailer.
Red is as good as skunk pee. Pour some on the floor and try to light it; you'll need a torch. Once lit it will smoke and stutter and stall out, leaving an ugly greasy stain on the concrete.
Modern non-ethanol gas, stored in a vented car gas tank, is good for about a month, maybe as much as two, but starting will suffer. Oxygenated is about half that in winter, one week in summer, or less depending on the ambient and if it sees the sun, like in a plastic gas-can..
Color is a pretty good test
Stabilizer will take even alcoholized gas to a year or more, here in Manitoba..

My factory ECUs have always been good down to 9.5v

As the gas ages, the more volatile compounds evaporate leaving the more syrupy, harder to burn compounds behind, which become more and more concentrated over time. To continue burning it, you will need to use more and more of it by increasing the throttle opening....... which drives the AFR ever leaner. A lot of that Orange gas is gonna go straight thru the engine unburned, and stink up your garage. And IDK what your AFR is gonna make of that.

EFI cars have relatively sealed fuel tanks and even a year later still start and run well. Course I guess the computer is probably working overtime.....
 
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I'm sorry, guys....I forgot to update this thread until now.
I did get lucky and the friend of mine that owns a carburetor rebuild shop was able to find a choke kit for this carburetor. He rebuilt the carb and installed the kit. The old gas was pumped from the nearly empty tank, fresh 91 octane went in. The car started up and ran fine but the choke wasn't working and the fast idle cam was not adjusted either. It ran much better on the warm-up but I figured that the main problem was old gasoline, not any fault within the carburetor itself. I was happy that it started and ran as it did before but I have yet to fine tune the choke adjustment and fast idle. I got distracted with the other Charger project...The replacement of the front structure as shown in the "Lookie what $5000 buys you" thread in the Members Restorations forum.
The carburetor guy thought that the 850 was a big carburetor for this engine but I reminded him that it is a vacuum secondary unit and that the Thermoquads were 800 and 850 cfms and they were on smaller engines.
 
Back up and behaving, good news!
And fwiw...not saying your carb builder is right or wrong but an 850cfm carb is NOT too big for your nicely-built (493?) Even slightly modified 440s usually love the bigger carb, I know mine does. I put on a 750 quick-fuel, tuned it to the max and eventually went back to my mech-secondary 850 speed demon. My engine is a 440/+.060 with a hair less cam than yours. The 750 was a little better for the first 1/2 second of throttle but the 850 kicks it's butt the rest of the way.
 
Thanks. I am running the 528 solid MP cam with 1.6 rocker arms, 2" headers and ported Edelbrock 84 cc heads.
I have a '75 Power Wagon with a 440 and since it rarely revs past 4500, I have a Holley 600 on it because the dual pattern intake allowed me to use a carburetor I already had. The original Thermoquad needed a rebuild and I just needed to get it running quick. The Power Wagon seems to run fine with that small carburetor. I recall reading that the 440 4 barrel from 67-71 used a 580 cfm Carter.
 
After reading this thread I started thinking, as scientists do sadly. ha.

I wonder if one could use a piece of tin foil? throw that over the carb with a hole or two to simulate a choke and then pull it off after the idle goes up.
I'm gonna try that. I do have manual working chokes but it seems with the -30F - 110F temp swing here in MN I'm adjusting them throughout the year.
 
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