Carter BBD Factory Settings

[StiffyLS]

Hi, what are the factory settings for the Carter BBD's mixture screws?

Thanks

[MagicRat]

You mean the idle mixture screws?
Usually the base line setting is to turn the screws in all the way and then back them out one and a half turns.

At that point you ca turn them a bit to fine tune them. One way to do so is to warm up the engine, and plug in a vacuum gauge to a manifold vacuum source (this is a souce that sucks most at idle)

You should show about 18-22 mmHg of vacuum at idle. Then turn the mixture screws in or your a bit until you reach the highest possible vacuum reading at a normal idle speed.

[StiffyLS]

Thanks a lot MagicRat, yes, I meant idle mixture screws, sorry. I'm having difficulties getting my carb set right, or maybe it's not a carb problem, I just converted my jeep's orginal 1 barrel manifold/carb to a 2-barrel manifold/carb with a remanufactured Carter BBD, got the intake/exhaust manifolds from a jeep junkyard near where I live. Jeep will start right up with a few pumps and idles great, alot better than my wore out Carter YF (1barrel). But when it's still cold and I step on it, it will bog out within the first second or two. After it's warmed up, I can step on it for maybe 3-5 seconds before it bogs out. I just set the timing to about 9 degrees BTDC which my haynes book told me to set between 8-10 degrees, on a 1 barrel it's set to 6-8 degrees. After setting my timing I did notice a great improvement, but still the same problem. I'm going to replace my plugs, wires, cap and rotor to see if that will help, but if you know of anything else I should check, please let me know... I also put on a new fuel pump not to long ago when I was trying to put on a Tomco remanufactured Carter YF and was having leak problems at the base of the throttle body, even tried 2 of them with the same problem, Tomco sucks.

Pretty sure I got the idle mixture screws right around 1 1/2 turns out too.

Thanks for any help.

[MagicRat]

The idle mixture screws work pretty much for idle only. As soon as you step on the gas the main jets take over the job. If the idle is good, the idle screws are not your problem.

Okay, I am looking at an exploded diagram of a '77 Carter BBD right here.

This carb uses moving metering enrichment rods, with a calibrated spring. Manifold vacuum keeps the rods seated in their holes during low speed operation. The rods act like plugs and prevent fuel flow through these holes.

However, as soon as you open the throttle a lot, the vacuum drops, and the rods rise up on the calibrated spring, allowing the holes to become uncovered and provide additional fuel into the engine.
If these rods do not rise when you step on the throttle, the engine will run too lean and die when you step on the gas, but will run fine at idle and low speed operation.

I sustect the metering rods are not rising; they are stuck down. Either the calibrated spring is missing or the tiny sliding piston that makes the rods move is stuck.

Also, its possible you have the wrong carb to manifold gasket, or the carb was incorrectly assembled.

IMO try another carb or complain to the remanufacturers. If this does not work, get a rebuild kit for the carb and go through it yourself.
IMO reman carbs are often poorly assembled and have defects. I always rebuild the carbs myself carefully. They are simple devices once you understand the principles involved.

[StiffyLS]

Thanks again MagicRat, put new plugs, wires, cap and rotor on and that didn't help much, alittle more responsive, but that's because my jeep needed new plugs and stuff anyways. So now I pretty much narrowed it down to the carb, I'll pull the top tomorrow and check if the metering rods are working correctly, I thought since this was remanufactured that I wouldn't need to do this, but then again, since I did have 2 Tomco reman. carbs that had problems, it would figure these guys don't take their time rebuilding them. The Carter BBD I have now was reman. by Champion and have had a lot less problems, besides the full throttle problem. Also, at half throttle, I don't get nearly as many bog-downs as full-throttle but it still happens.

Thanks!

[oljeeptek]

Magicrat is possibly on the right track.

I'd also be sure you aren't getting any egr flow at low temps. Disconnect/block it to check.

I have also had these break the pickup coil wires in the distributor. Plug the vac advance hose or lightly pull the wires in the distributor sensor and see if they stretch or come apart.