Carb Adjustment?

[BigFishBobby]

Here is my diagnostic so far:

1) I have heavy exhaust (not smoke, although it looks like smoke ONLY on humid nights).
2) I am not burning oil or losing water.
3) During the day I have a strong exhaust smell from the tailpipes, but no smoke.
4) I bought the truck from a guy who lived in Ga. who bought it a couple months prior from a guy in N.C.

Is it possible that due to the altitude change from NC to here that I need to adjust my Carb? Is it possible that is my strong exhaust odor problem? Is it something else completely?

Thanks in advance for the input.

[motopatzo]

Do you actually see smoke (what color is it if you do) or are you getting that unburnt fuel smell?

[BigFishBobby]

The only time I see "smoke" is on humid nights. Never during the day, which leads me to believe it is not "smoke" at all maybe just fumes or something to do with the temperature outside vs. the temperature of the exhaust. Weird I know.

[motopatzo]

It probably is moisture content in the exhaust process. We get that here as well on cool mornings. Part of the combustion process. On newer vehicles with all the emission equipment, you can actually see water drip out of the exhaust when you first start them up. However on yours, if you can smell strong exhast odours, it could possibly be jetted too rich or your idle set too rich?

[BigFishBobby]

However on yours, if you can smell strong exhast odours, it could possibly be jetted too rich or your idle set too rich?

Thats what I was also thinking. Just wanted to hear other options. The odor is what has me really asking questions. It doesnt smell like oil, and I am not losing water so I have a hunch it is the carb. Thanks.

[mnunn454]

When I got my El Camino, the car ran fine, but the exh. fumes were so bad they'd run you out of an open door 2-car garage in less than 30 seconds. Turned out to be running way too rich. A jetting change and a few other adjustments did the trick.

On my C-10 I recently installed O2 sensors in the header collectors and an A/F ratio gage in the dash. While it's not nearly as good as a wide-band O2 sensor setup, it did help me refine the tuning of my carb to get the Air Fuel ratio in the ideal range most of the time.

I'm assuming you've already eliminated the "stuck choke" possibility. Next step is to check your plugs. If they're dark/sooty/crusty with carbon or wet with gas, that's a sure sign the jets are too rich. A good bet is to start with jet sizes the same as would come in a new carb of the same type and then go up/down from there. What kind of carb do you have? Do you feel confident enough to change th ejets yourself?

[BigFishBobby]

Originally Posted by mnunn454

When I got my El Camino, the car ran fine, but the exh. fumes were so bad they'd run you out of an open door 2-car garage in less than 30 seconds. Turned out to be running way too rich. A jetting change and a few other adjustments did the trick.

On my C-10 I recently installed O2 sensors in the header collectors and an A/F ratio gage in the dash. While it's not nearly as good as a wide-band O2 sensor setup, it did help me refine the tuning of my carb to get the Air Fuel ratio in the ideal range most of the time.

I'm assuming you've already eliminated the "stuck choke" possibility. Next step is to check your plugs. If they're dark/sooty/crusty with carbon or wet with gas, that's a sure sign the jets are too rich. A good bet is to start with jet sizes the same as would come in a new carb of the same type and then go up/down from there. What kind of carb do you have? Do you feel confident enough to change th ejets yourself?

I have not eliminated the "stuck choke" possibility. The truck runs fine and starts after pressing the gas once before start up. I have an edelbrock carb I believe. I do not feel confident in changing the jets myself yet, but with some info maybe I'd get brash.

[mnunn454]

Bobby, I'm new to the site so, pleased to meet you. (Nice Red 69 C-10 BTW).

I have an Edelbrock carb and am fairly familiar with adjusting it.

Once you've verified the choke isn't sticking shut, Edelbrock carbs are fairly easy to adjust jetting. Swapping the needles to smaller ones is the simplest and takes only about 3 minutes once you're familiar with the process. You don't even have to pull the top of the carb off.

Another possibility that I overlooked in my 1st post above is a fuel bowl needle and seat that's sticking open and letting extra gas pour into the carb. Fixing that, or swapping to smaller jets is straight forward and not as messy as when working with Holley carbs.

There's another oddity that could be causing it, and that's if the engine has low vacuum due to a radical cam or a vacuum leak. How much manifold vacuum do you pull at idle? Is there a vacuum leak? What are the specs on the cam? If the vacuum is too low, the "power mode" springs will lift the needles and cause it to run richer.

Finally you might want to check the idle mixture adjustment screws to make sure they're open only about 1.5 turns (give or take a little).

Good luck. Let me know what you find.

[BigFishBobby]

mnunn, welcome to the forum from a fellow newbie. Thanks for the input. I'll do some research and check it out. Thanks again.

[Boog]

If you are using a quadrajet carb there is a thread down in the engine forum with a LOT of links to tuning the quad carbs. I just found it and saved that one to my favs.

[motopatzo]

I'll have to agree with mnunn454........that's exactly what I was thinking