Carb running rich

[joshm121]

Noticed exhaust seems to have really strong smell. I've heard of a carb running "rich"before like too much gas and wondering if I need adjusting. Tried small screws on side but no difference. Need some feedback on proper way to adjust.

 

[savage]

What carb do you have? It sounds like a holley if you are adjusting it on the side.

 

[joshm121]

Sorry, yes, holley 2b.

 

[dave67fd]

Tried small screws on side but no difference

No difference in what? The smell?
Random changes in the mixture screws will cause you problems unless you follow the proper procedures.
First check that the float level is correct and then use the following to tune.


http://forums.holley.com/entry.php?429-How-To-Adjust-The-Idle-Mixture-On-Holley-Carbs

 

[DirtDonk]

When does it smell? All the time, or just at idle? Or just when accelerating or some other time?
The two screws usually only control idle mixture so would have an absolutely minimal effect on driving smell.

Is this a new thing? Been doing it since you bought the Bronco? Just noticing it now that the top is off or the windows open more often maybe? That last is a very common thing. These old carbureted engines were not the cleanest burning to begin with, so perhaps what you're smelling is more "normal" than you might think, but it's just now getting into the cabin more.

Paul

 

[joshm121]

I think it has always had a strong smell, but I definitely notice it more now that the top is off, and I definitely smell it while moving. Maybe normal, but it is pretty strong. So much so that it gives me a little bit of a headache. Gas mileage is pretty terrible too (about 10 mpg).

 

[77BRONKOTN]

Real strong smell is lean. Like burning your eyes etc.

 

[joshm121]

Doesn't really burn my eyes, but could see how it could. How do you correct?

 

[ransil]

fix your exhaust

 

[joshm121]

fix your exhaust

care to elaborate?

 

[DirtDonk]

I'll chime in again. Pretty sure ransil is referring to the place your exhaust tip(s) exit the rear. BEEEEG problem on Broncos, aerodynamically speaking.

I was asking for the other details pretty much to find out the same thing, and if what you were experiencing might be related.
Broncos have sucky aero, and the exhaust exit is critical and a very narrow window. Turn-downs are a no-no. Exiting ahead of the rear tire is a no-no. Even dual exhausts is sketchy at best, and the single best place to exit the exhaust is behind the passenger tire angled out to the side, or slightly to the rear. NEVER straight out the back.

Any of that apply to you?

Paul

 

[DirtDonk]

Oh, and while rich-or-lean conditions definitely make things worse, just about any normally running carbureted engine of this vintage has some pretty heavy exhaust smell. Only the most finely tuned and perfectly running carb'ed engines are easier on the nose.

With the top off, two things happen. One is that a lot of the exhaust is naturally sucked back into the passenger area over the tailgate. And more important sometimes the exhaust gets sucked heavily into the cabin through the previously closed off corner stake pocket holes.

For starters, to maybe lower the death-fume quotient just a bit, try stuffing some rags/shirts/furry cats into the corner holes to see if that might slightly reduce the amount of fumage you're getting.
Worth a shot. Especially if it works!

Paul

 

[DuctTape]

I'll chime in again. Pretty sure ransil is referring to the place your exhaust tip(s) exit the rear. BEEEEG problem on Broncos, aerodynamically speaking.

I was asking for the other details pretty much to find out the same thing, and if what you were experiencing might be related.
Broncos have sucky aero, and the exhaust exit is critical and a very narrow window. Turn-downs are a no-no. Exiting ahead of the rear tire is a no-no. Even dual exhausts is sketchy at best, and the single best place to exit the exhaust is behind the passenger tire angled out to the side, or slightly to the rear. NEVER straight out the back.

Any of that apply to you?

Paul

Turn downs when exiting side behind tire is a no-no? I did not know that. Is that because it splashes to rear and gets sucked up and in?

 

[jckkys]

I think all of us who've owned /driven EBs for 40 or more yrs. have wrestled with exhaust fumes getting sucked into the passenger compartment. Early models like my '69 and '73 had OE tail pipes go around the rear tire and angle to the rear. This worked fairly well but I backed into a rock and bent/kinked the pipe. The '77 had the tail pipe point straight to the side in front of the bumper with 90 degree bend to exit straight back under the end of the bumper. This one tended to come in the lift gate when it was open. A knuckle head exhaust guy replaced that with duels that are too noisy but exit at a 45 degree angle just under the ends of the rear bumper. This seams to be the best at keeping exhaust out of the passenger compartment. It may be tuning, but I don't smell exhaust in or around the Bronco. My EFI cars smell like sulfur when they start cold.

 

[joshm121]

Ah, OK, very helpful. I do have duel exhaust. They exit at 90 degrees, but maybe that is still the problem. Is the recommendation 45, or does it really need to be a single exhaust system? Will try sealing up the pocket holes and update.

 

[DirtDonk]

Turn downs when exiting side behind tire is a no-no? I did not know that. Is that because it splashes to rear and gets sucked up and in?

No, I was referring to the generic "turn-down" where they simple terminate the exhaust tubing right at the back of the muffler under the truck. Just aim it at the ground about the area below the back seat. Not a good idea on most EB's.
Some do it and don't have much to complain about. Even Johnny here at WH has that I think. But his EFI runs really well, and his rear window is rarely open unless the top or sides are off, so lots of fresh air in the mix anyway.

Turning the tip downward after exiting the rear is not a bad idea in fact.
Might even work better in some cases than a simple side exit.

Paul

 

[DirtDonk]

Yeah, even though I prefer the single, I would think a dual that's already there might be ok until you determine for sure that the angles/exit points are the main culprit. Definitely seal things up first and see if it helps.
Be great if it cures it completely, but it's a rare Bronco that doesn't get at least a little crap blown in from the exhaust.

Paul

 

[DuctTape]

No, I was referring to the generic "turn-down" where they simple terminate the exhaust tubing right at the back of the muffler under the truck. Just aim it at the ground about the area below the back seat. Not a good idea on most EB's.
Some do it and don't have much to complain about. Even Johnny here at WH has that I think. But his EFI runs really well, and his rear window is rarely open unless the top or sides are off, so lots of fresh air in the mix anyway.

Turning the tip downward after exiting the rear is not a bad idea in fact.
Might even work better in some cases than a simple side exit.

Paul

Ok I got ya and glad to hear it. I have mine exiting straight out side behind rear tires and I was planning on turning them down to point to ground. Wife is getting tired of black spots on her car. .

 

[DuctTape]

Noticed exhaust seems to have really strong smell. I've heard of a carb running "rich"before like too much gas and wondering if I need adjusting. Tried small screws on side but no difference. Need some feedback on proper way to adjust.

If carb tune doesn't solve the problem, ignition system can also cause rich/lean. Fuel system can also cause lean condition.

Spark plug appearance can be used to help diagnose if it is a rich/lean problem, but it is more art than science.

As others have said it might not be a rich/lean problem. 10 mpg is pretty good. If I were you I would pull plugs first to check how they look (google for example images).

If you have the wherewithal, finding someone with a tailpipe wide and mixture reader can help diagnose. From my own experience it can be difficult to nail down the true problem just from the usual suspects of smell and plug condition.