To Choke or Not to Choke

[friz freleng]

'73 Ford 302. I have just installed an Edelbrock 1405 carb (manual choke) on the engine. When I start it I have to keep it reved above 2000 RPM, until it reaches operating temp, or it will not idle. After reaching operating temp, in a few minutes, it idles nice around 600-800 rpm. The idle screws are set 1.5 turns out. It idles a 10 degrees BTC. I am assuming a choke, manual or electric will cure the cold idle problem? I live in north central Florida. Temps are in the 40's at night and 60's - 70's in the day. I was going to buy/install a choke cable but, for $35 I can get an Edelbrock 1478 Electric Choke Kit on Amazon. Any advice appreciated. Thanks

[miker98038]

You need to hook up the choke, and set the fast idle settings. Read the manual, it’s not complicated but you need to do it all properly. I ran a 1406 with a manual choke on my bird for several years, and it’s a very similar carb.

I suspect something else is wrong. My F code clone had no choke, milled completely off the carb. But even it at 40 would start to idle down before the temp came off the peg. No heat crossover in the intake, but after you got some heat in the heads it only needed a little throttle. The engine had enough cam it idled from 900-1000 warm.

[Flathead Fever]

I was a smog mechanic for 30-years and a Mustang hot rodder. Tuning has to be done in a certain order. The first thing is to set the timing which you have done. 10 degrees is good; it's the factory amount on my original '66 Shelby. Next You need to set the idle mixture warm, just 1 1/2 turns out is a place to start just to get it started but then it needs to be fine-tuned. You need to turn each idle mixture screw "in" the same amount on both screws maybe a 1/8 of a turn at a time, until it just starts to affect the idle mixture, then back them out evenly just a little at a time until it smooths out. Once you have the idle mixture adjustments maybe turn them additional 1/8 of a turn "out" or all-around driving, because of weather changes the mixture can change a little bit day to day. Both screws need to be turned out "exactly" the same amount. Now if you changed the "idle rpm" after adjusting the air fuel fixture you might want to check mixture again.

You can also take a bottle of propane and just barely open it and pass it over the carb. if you have the mixture adjusted correctly it won't have any effect on the rpm but if it is to lean the idle will go up and if it's too rich the idle will go down.

The last idle adjustment is the choke. Once you have the idle mixture set then let the engine cool down. Wait until it's a cold day and then make the choke adjustments on the electric choke or manual cable

Then you can start playing with the jetting to really get the carb dialed in. There is a lot to a carb to really get it dialed in.

[friz freleng]

Thanks for the advice. I just ordered an electric choke kit. Just to be sure, I am going to wire it to an ignition hot wire/source. When I turn the key on, 12vdc goes to the choke and stays on until I turn the key off. Yes?

[dmsfrr]

Depending on which carb and choke mechanism you have there is usually a separate adjustment screw on a 'fast idle cam' just below or behind the choke thermostat cover. Maybe not as easy to see as the one in the red circle in this first example photo.

I wired the electric choke to the 12v side of the ballast resistor in my 12v converted '55.
Example photos 2 and 3.
Your 302 may have a Pink resistance wire instead of a ceramic ballast resistor. That Pink wire may be under the dash not in the engine compartment so double check voltage at the coil.
.

[miker98038]

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As dmsfrr shows above, there’s a fast idle cam. If your 1405 is the same as the 1406, there’s a couple steps on that fast idle. One for full choke, and one for pull off or as the choke opens. Read the manual. Getting the right compromise between the two is essential for proper start and operation. May take some fiddling to find the sweet spot. Depending on where you live (temperature variation) it may also require a slight seasonal adjustment on the choke housing. Fall and spring. Common back in the day with any auto choke.

[Gene F]

I have both on my cars. I rally like the electric choke.

DMSFRR, I hate to nit-pick, but when you use the choke cap that is not electric it has been my experience that you need the clamp that holds the heater hose against the cap for it to work correctly. Just my experience...

[BW]

Yes only when the key is ON. A lot of people use the S terminal on the back of the alternator, I know it's between 7 & 8 volts but everyone I have talked to say they have not had a problem.