Carter BBD tuning issues

-
W

watso76

Active Member
Joined
Apr 28, 2014
Messages
31
Reaction score
0
Location
Jacksonville, NC
I have a stock 318 with a Carter BBD 2 bbl. It was running fine before but quite a bit rich. I did some tinkering after looking at my manual to try and lean it out. I felt like it ran better but when I put it in gear it idled very low. I essex with the fast idle cam and the curb idle screw the mixture screws and now I can't get it to run smooth again. It idles well but as soon as I rev it there is an initial stumble but it breaks through and sounds rough. It only does it initially. I just want to get it back where it was. Does anyone know where I should start fresh? What should I set everything on? The fast idle cam is an enigma to me even after following the instructions in the manual to set it. Where should I start my mixture screws at? Any help to get it running smooth would be great. Thank you in advance.
 
Ignore the fast Idle, with the throttle closed, turn the adjuster out approx. 2 1/2 turns. some need only 1 1/2, depending on the year. Turne the Idle screw until you get a good idle. Make sure the timing is static at the setting the book calls for. vacuum unplugged and tapped off.
 
Check to see that the metering rod lifting mechanism still has the set screws tight. Your rich condition could be due to a misadjustment of that set up with the power piston and the metering rods.
 
oldmopardude, which vacuum hoses do I need to unplug? Which adjuster do I need to screw out? The fast idle? It is a 76 Scamp btw. Sorry, I'm new at carbs.

airgrabber, how do I check any of that? I'm new at carbs and don't have a whole lot of experience with them.
 
Now that we know it is a 76', then I believe the Instruction sheet suggests 2-3 turns of the air mixture screw counterclock wise as a static setting.(right fully closed, then 2-3 turns left) don't screw the mixture screw too tight, just snug,barely. The vacuum hose to the distributer should be disconnected, so the timing won't advance at Idle. I seem to remember that year not having vacuum at an Idle anyway.
Once timing is set, look for 550-650 Idle rpm. Check timing again, and again as you adjust the Idle/mixture screw. you turn it in 1/4 Increments left or right to get the best Idle, smell for richness,etc. Once you are satisfied, get somebody to put the car in gear with the brake on to adjust the rpm so it will still maintain idle in gear. a slight drop in rpm is normal. It is a lot easier to show you than explain, sorry. fast idle asjustment is primarily for maintaining rpm during warmup, no other time.
 
warmed up, choke wide open. you will have to use your best judgement, the engine should be smooth running,without banging into gear. if it does, the idle is too high.If the engine shudders, idle is too low. remember the high idle lever is operated by the choke. none of that is connected to adjusting the carb. do all this after the engine is warmed up, and the choke is off.
 
So the choke should be wide open when the engine is warm? I didn't think it was suppose to be. Or am I suppose to open the choke and keep it open while I adjust? When the carb is cold and nothing has been touched, what should I have my settings at? Idle mixture screws, idle speed, choke, fast idle just as a baseline.
 
all adjusting is done warmed up. the choke is closed upon start-up,and opens about a 1/4 when started,and high idle lever holds the throttle at a slightly higher RPM. The choke has to be wide open to do any adjusting of the fuel/air mixture screw. Remember, the choke has nothing to do with air/fuel adjustment. The choke helps start the car, then opens up gradually. only when it is wide open do you adjust the carb.
 
If the choke is not fully open when warm, that's why its running rich. With the butterfly not fully open when warm, the air/fuel ration is off. Less air, but more gas. When the butter fly is fully open when warm, you'll have a air/fuel ratio. But until that butterfly is fully open when warm, you're just chasing your tail. Didn't mean to insult you with my explanation, it seems as though you don't have a lot of experience.
 
Louie70Dart said:
If the choke is not fully open when warm, that's why its running rich. With the butterfly not fully open when warm, the air/fuel ration is off. Less air, but more gas. When the butter fly is fully open when warm, you'll have a air/fuel ratio. But until that butterfly is fully open when warm, you're just chasing your tail. Didn't mean to insult you with my explanation, it seems as though you don't have a lot of experience.
Click to expand...

That makes sense, so what do I need to do to get it open all the way when it's warm?
 
Not very familiar with that year BBD. Is there a release? It might be an adjustment to the linkage itself? There is a cam on the gas linkage side, at least on the BBD for my 70. Its stepped so the choke opens dependant on how warm the car is.
 
Not sure if there is a release. I will look in my manual. I will be studying that tonight apparently. So much more involved than I thought it was going to be.
 
Don't let yourself get intimidated. It looks complicated but the idea is very basic. It don't have a mind of its own. Make it do what its supposed to do. It could be as simple as an adjustment.
 
What exactly does the choke vacuum kick do? Anything? It has a linkage connected to the choke on the other side of the carb.
 
When the engine is cold the thermostat rod wants to closes the choke 100%.
To start push the pedal down once and release, this allows the choke to close and the weighted fast idle cam to fall catching the screw and opening the throttle blades.

Now you start the engine and it creates a vacuum THIS pulls the choke blade open slightly. (Choke Pull Off or Kick). I'd set my 1970 at 1/4 inch.

As the engine warms the thermostat rod tries to open the choke and take it off of fast idle, this will only happen when you push the gas pedal again.
 
Thermostat rod? When my engine is warm I can move the choke to wide open but it doesn't stay there. What can cause this?
 
You must log in or register to reply here.
-

Back
Top