Still Chasing Carb Gremlins
 

I fixed the choke and vacuum leak issues with my carb, but it still isn't perfect.

When I start the truck in the garage (50-60 degrees) it starts and idles fine. When I start the truck outside (20-30 degrees) is starts and runs fine for about 30 seconds, then idles down and sounds like it is going to die. If I give it a little gas it picks back up but runs very rough and shakes the truck. After 1-2 minutes of holding my foot on the gas it smooths out and runs ok until I get home and park it.

Again, in warmer weather it runs fine, but in cooler weather it runs rough. What do I not have set correctly?

Re: Still Chasing Carb Gremlins
 

Cold intake plenum.
Crossover (exhaust heat) under the intake might be plugged.
Your heat riser may be hooped or stuck.
Or you have headers which doesn't let the crossover work.

Re: Still Chasing Carb Gremlins
 

It is over chokeing. We need to know what make & model carb you have. The choke pulloff may be bad. It may be like Geezer says, the heat cross over passages plugged up & not getting heat to the choke coil. You need to fix this as excess fuel can wash the oil off the cyl. walls & pollute the oil.

Re: Still Chasing Carb Gremlins
 

It's an Edelbrock 1406.

Re: Still Chasing Carb Gremlins
 

What intake?
Do you have headers?

Re: Still Chasing Carb Gremlins
 

Edelbrock intake, and headers.

Re: Still Chasing Carb Gremlins
 

So then it's running like normal with no heat in the intake.
Not a problem if you let it heat soak.
When I start mine I listen to hear it start to slow down and run rough. I shut it off, go for a 5 minute wait and fire it up again. The 5 minute wait lets the heat rise from the oil and the lifter valley and heat up the intake plenum. You need heat to keep the fuel vaporized. If it gets cool it reverts back to a liquid and puddles in the intake. THen as you start to drive it keep your ears open for the sound of more rough running. Colder air coming into the carb cools the intake again. Usually it'll straighten out after a good soak in a mile.
Just the nature of the beast when you have an unheated intake.

Re: Still Chasing Carb Gremlins
 

Is there anything I can do to remedy that, or am I stuck with it running this way given my current setup?

Re: Still Chasing Carb Gremlins
 

I think it should idle better than that in 20 - 30 degree weather. Sub-zero: yeah, that's a challenge, but you can set it up to run okay in those cold temps.

First thing's first: confident that your warm idle mixture adjustments are right? Base timing is right? What RPM does it idle at cold and full choke (i.e. when you first start it in the morning)?

Before you start the motor, push the accelerator to set the choke, then pop the hood and look at the right side (driver's side) of the carb and note the position of the fast idle screw on the fast idle cam. At least close to the middle of the two lines?

Then go to the Edelbrock (actually this is a link from Summit) site and get their choke adjustment instructions (very bottom of this PDF).

http://static.summitracing.com/globa...-1478_inst.pdf

I think folks don't always understand how to adjust these things but really, if it's not all totally worn out, it's a decent setup.

Re: Still Chasing Carb Gremlins
 

I've lived with it for 50 years in a lot colder climate than where I live now. Winters of 40 below.
You can jet richer, max out your initial timing and turn your high idle up a bunch but depending on the temp and humidity you still might have the problem.

Re: Still Chasing Carb Gremlins
 

mine did this when I bought it last month. exactly problem you are describing.
I put new edelbrock intake, edelbrock 600 cfm carb, and HEI distributor and runs really good now.
I think the main problem was the old points system on the distributor.
not sure what you are running for ignition.
just a thought.
Mark

Re: Still Chasing Carb Gremlins
 

I richened my fuel screws by a 1/2 turn this morning and increased my idle by about 1/4 turn. My fast idle seems ok, maybe even a little fast when it kicks in. I have not checked my timing yet because I assumed it was right since it ran fine in the summer; I'll check timing tomorrow. I'm not sure what RMP it idles at because the tach that was in there was junk, and I haven't gotten a new one yet; I've been setting idle by ear.

Re: Still Chasing Carb Gremlins
 

What intake manifold?

How about a picture of the setup with and without the air cleaner?

Re: Still Chasing Carb Gremlins
 

jkeady & geezer are spot on, confirm all of your basic adjustments & learn what your engine likes. Carburetors are like women, you gotta get to know them! Some are more finicky, some are high maintenance! Actually, when set up right they are neither but every carb seems to have a method it likes to get it cranked in cold weather.

Re: Still Chasing Carb Gremlins
 

A vacuum gauge is helpful for setting both timing and carb set screws.
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Re: Still Chasing Carb Gremlins
 

I dunno... sounds like a completely normal cold weather carb start up to me. These old rigs with carbs are NOTHING like modern FI rigs.

Even setting the fast idle by stepping on the pedal and starting it up it can and will labor a little bit during cold weather.

What distributor do you have? If an HEI make sure the spark plug gaps are opened up to .045

Gary

Re: Still Chasing Carb Gremlins
 

That may be. This is my first time dealing with a carb, so I may have a wrong expectation when it comes to how it should run in the cold.

Re: Still Chasing Carb Gremlins
 

I'm betting that is probably the case. Having the luxury of modern FI makes the old carbs pretty archaic when it comes to cold weather. Being able to turn the key and just walk away from a vehicle without messing with the gas pedal is something we have all gotten very spoiled with in this day and age. Even older guys like me. ;)

Heck, I've removed every choke out of every carb I've ever owned. Just get used to pumping the gas and feathering the throttle when it's cold out. It turns into a real rodeo while driving a 4 speed. :lol:

Gary

Re: Still Chasing Carb Gremlins
 

That's what I've got, it's a trip.

Re: Still Chasing Carb Gremlins
 

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Re: Still Chasing Carb Gremlins
 

I've never had any luck with Edelbrock carbs lately. I've switched to Holley and have no problems.

Re: Still Chasing Carb Gremlins
 

I pressed the gas pedal once and it started fine. At 30 seconds I give it a little gas and hold it, at 51 seconds I rev the engine and let it go back to idle, from 1:02 to about 1:15 I get a few pops (like a backfire, but not as pronounced), I rev it again at 1:22 and let it go back to idle. It idled fine to the end of the video and I had no issues driving it a few blocks home.

https://www.youtube.com/watch?v=W4eO...ature=youtu.be

Re: Still Chasing Carb Gremlins
 

At 24 seconds in it starts to load up (too rich). Depending on ambient temp you may want to roll back your choke a little (the black round plate on the side) It also sounds like your fast idle is a little low (a higher fast idle will help prevent load up) Those noises did sound like backfires - a backfire is almost always ignition related, most fuel related backfires are when it is runnig very lean or very rich so check/adjust your mixture screws. (it's not popping at fast idle but it is at idle) also confirm timing, check ignition components (plugs, wires, cap, rotor) A cold engine requires more KV to light the mix so with worn parts it may run fine when warm but have a miss/stumble when cold.
Lets say, for sake of argument, that your mixture screws are almost all the way in (lean), your choke is dialed too rich, your plug wires are worn & cross-firing - You are dealing with three separate issues, don't expect one adjustment to fix everything. If it were me, I'd re-check my ignition system, if a part is suspect, replace it, adjust the carb using edelbrock's manual, set timing & go from there.

Re: Still Chasing Carb Gremlins
 

X2!!
Turn up your high idle and. lean your choke a bit.
The pops or backfires is because it's puddling fuel. It's lean.