First off this is my first carburetor. I have a 66 f100 350 with a 352 ford carb #c6tf t. I rebuilt it tonight after taking it apart and soaking it in chem dip for a day. What are the adjusting screws on the bottom of the carb for? They have springs on them. I know that neither is the idle adjuster. Thanks for the advice. Also do you guys recommend using the lead substitute?

 

Those are the air/fuel ratio screws. screw them in all the way then out 1.5 turns. with the engine idling once warmed up then slowly adjust each one out until idle starts to drop (due to it being to rich) then screw back in 1 turn. at least thats how I was always told how to adjust them. good luck

 

The mixture screws are for the idle circuit only. 1 & 1/2 turns out is a good rule of thumb for the idle mixture screws. Just don't over tighten them when you screw them in or you can damage the seat.

 

Old trick if you dont have a tach to use when making your adjustment was to put a half full glass of water on a flat surface on your motor and watch the water as you make your adjustment. Like I say a tach is better to use but the glass or water will do in a pinch. Sometimes your ear or sense of feel when adjusting the carb can fool you.

 

ok the carb is in, it works much better, but it still wont idle as low as I want it to, my guess would be that it's idling at 1200, anything lower it dies. Although when I have the choke on it idles great, probably 600-800. Any ideas? I tried all different adjustments with those screws.

 

When you do the adjustments make sure the truck is up to temp before adjusting...idle is 500-550...mine doesnt like running that slow much either.

- cs65

 

I had it at temp. What else should I be looking at to get it to Idle?

 

did you check the timing?

 

you might make sure you have no vacuum leaks. check all hoses, T's and carb ports.

 

A bit backwards. Idle will drop or kill engine when it goes lean. Idle screw turned in too far.

Use a vacuum gauge for highest vacuum or a tach for highest rpm.

Start off closer to 2 turns. Go back over each screw until you get the best idle.
For best emissions turn them out to highest vacuum then in until idle just starts to drop off.

Have you checked the points and dwell? (assuming you still have stock points system)
Where is your timing at with vacuum advance disconnected? Stock is 8 Deg before but they like 12+ BTDC much better for initial. Are you sure the idle circuits are all clean? Do you notice a big diff when turning Idle mixture screws?

 

If it runs ok with the choke partly or mostly closed it sounds like you have a very lean condition (too little fuel mixed with the air). Look for any large vacuum leaks. If the truck has a PCV valve, pinch off the vacuum line between the spacer plate and the valve to see if the idle improves. If the PCV valve goes bad it can cause a large vacuum leak in these trucks. If the PCV valve is OK look for other vacuum leaks with a can of carb. cleaner. When you spray an area with a leak it will cause the idle to come up and smooth out. If no leaks found, back the air fuel adjusting screws out as far as you can w/o falling out and see of idle improves.

 

Ok ill be checking for vacume leaks, the timing is another story. I installed a pertronics unit in the truck because the points were worn. That helped a lot. I have to do some more resedarch before I tackle timing it. I'm grabbing a vacume guage from work today.

 

well looks like im going to be pulling the motor. I have vacuum leaks around the intake manifold now three broken bolts on the exhaust manifolds and now the freeze plug under the motor mount ( the only one that I didn't replace) is leaking so I figure that i am going to save my self a lot of head aces if I just pull the motor. I ordered the felpro engine kit so i am going to replace all of the seals because i am sure that they are leaking. I'll be pulling the heads and replacing the head gaskets, and valve seals. I will also be inspecting all the bearings while im in there and maybe do the rings.

What else should I be doing while I have the motor pulled? Is there anything that I need to be aware of before I tear into it that is special to these old trucks?

 

Thats a great carb to learn with. In the late 60s-early 70s we had this thing called a Quadrajet on big block GM's that you had to throw out because they never worked even right out of the rebuilt factory box.

 

Ok, so the motor is finally in. Still having some idling issues. The pcv valve is new, The timing is set at 10. It will still only idle in choke. and it wont idle very low there. I don't have any vacume leaks. I set the timing with the vacume advance disconnected and the hose plugged. The fuel air mixture screws don't seem to do much of anything. Even with the idle screw all the way in it still wont idle with out the choke. I can push the choke about 50 percent of the way in before it idles down and dies. Any help would be great.