Technical Why is my SBC running on?

This is exactly what I'm trying to say. The slots being open too far means that something else is wrong. I think it's your timing and converter.

 

By "opening the throttle plates more" I just mean turning the idle SPEED screw to open the throttle a bit more to increase idle speed. Though once they're opened beyond a certain point, as mentioned above, adjustment of the idle MIXTURE screws can seem to be ineffective. Especially if the throttle plates are open enough to allow the carb to start pulling fuel from the main nozzles.

Get yourself a vacuum gauge if you don't already have one. It will teach you a ton about what's going on in an engine and carburetor and WHEN it's going on. Hook the gauge up to full manifold vacuum in a stock daily driver and watch how it reacts during normal driving for a couple of days. Now hook it up to something with a lumpy cam and a tight torque converter and watch the gauge for a couple days of normal driving. Then scratch your head and ask yourself "Where the hell did all my manifold vacuum go?"

As also mentioned above use both the vacuum gauge and a tach when trying to set the idle. What you're looking for is the "lean best idle" settings. You want the highest, steady vacuum reading and a relatively low, steady idle speed. More initial timing will help bring the vacuum up, but you may have to make some adjustment to mechanical advance so you don't end up with too much total timing. It all kind of turns into a big balancing act, just like in the circus! Some lighter springs under the power pistons may help as well. An easy mod on the Edelbrock/Carter carbs.

And keep in mind that you sort of have to do this twice. Once to get a steady idle in neutral and once to get a "liveable" idle in gear with the torque converter trying to lug down the engine. You'll see what I mean when you look at the vacuum gauge.

 

There have been a couple of times in the past that I have cracked the secondaries a little more and backed off the primary side to kill the flow through the transfer slots at idle. Folks used to drill holes in the throttle blades too, but we won't talk about that.

 

Hi Burger,
I really appreciate the ***istance. I wasn't really clear and I apologize for not making my self clearer. I know that the idle mixture screw will increase or decrease the slot. I thought that by other means you could adjust them through the another method (ie) a bench set up method. Never mind that. lololol
Jay

 

I agree with you here Flathead. THat is why I am going to root out the problem properly.
Jay

 

Ok. Thanks to the guys that are hanging in and trying to help me solve this problem. If you guys can be patient I am super busy this weekend and will be back on later on. I am also going to find out what gear is in the diff. I will get back to this thread and we can continue later on. I really appreciate the tuning tips big time. I am totally willing to learn and take advice and Remember this is not my car. It is a friends. I appreciate everyone's comments that have been really helpful. This is why I love the HAMB!
Jay

 

You said "I set the air fuel screws 2 turns out and set the idle".. Did you adjust the mixture screws any more after you got the engine running?
These "2 turns" is only a base number, and on the rich side, and will cause running on..
Slowly wind each screw in 1/4 turn each side, till it starts to run rough, (you will probably have to adjust the idle speed as you do this) then back them out a little to get a smooth idle. .. My mixture screws are approx. 3/4 turn out..

 

No....the slots are fixed holes in the carb. They are not adjustable. What you can do, is adjust the idle SPEED, and it will expose more or less of the slots, as the throttle blade moves up or down.