Whats goin on yall. I gots me a 4 barrel rochestor and am having a tough time tryna figure out how to tune it correctly. I understand theres two mixture screws in the front but when i have the car at idle and i turn em. The sound of the engine still sounds the same. Which makes no sense. I mean i dont know. But can u guys tell me how to do this correctly ?

 

Which Rochester is it?

 

E4ME

 

those screws won't really do a hell of a lot on that particular carb- they set them from the factory and plug the holes so you can't screw around with them, and they really don't do as much as the mixture screws of an older non electronic carb, since their function was mostly taken over by that electric solenoid that is in the carb.

but if you want to try to adjust them, take them out and blow the holes out with a good shot or two of carb cleaner- stick the straw right in the hole and blast away.. when you put the screws back in, gently bottom them out and turn them out 1.5 turns and go from there. but you need to make sure the engine is totally warmed up and the choke and fast idle cam is disengaged before even trying to do anything with them... back off the idle speed screw as far as it can go before the car wants to die, then adjust the mixture screws for the highest idle and highest vacuum reading.

 

Ok well lemme ask u. Is this
Normal. That when i start the car its at 1500 rpms and then when i pressed the accelerator and let off to go back to idle it stays around
700

 

That is the choke working. After engine warms and you step on the accelerator, the choke mechanism allows the idle to drop down.

 

Dang. Looks like i fked up....car was starting nice this morning but then in the night the
car dont start up. So am sitting there sayin to my self. Wtf is going on,, i just put a new tank and pump and i got fuel pumpin nice. So i sprayed the carb with a lil starter fluid. It didnt start so am like iight its not a fuel problem. So then i check for spark. I niggarig the wires and got spark from each one. I then took the #1 spark plug out and this
Sht was coated black smelling like unburnt gas.. And real talk. I thought i
Tuned the carb right. But I guess not. I got no idea how ama get the carb right. It just be getting to confusing . Any body got any solutions?. Cause i guess i tuned it to rich. (this car is a 85 Iroc H.O.)

 

Hey. Shep. The screws down in front of the carb allow air around the closed butterfly valves at idle. A good way to adjust them is to open them both equally 5 turns and start the car ( warmed up ). Turn them in 1/4 turns each till the idle speed drops 100 rpm. That should be 2 to 3 turns from closed. If the exhaust pops on coast down, close them down another 1/4 turn each until that stops, not less than 1 1/2 turns open.

 

Actually, no.

 

Hey thanks yall but i got it.. I turned them closed then backed it out about 2-1/2,, it sounded like it was dieing and plus the car was setting a engine light of lean exaust, so i started to turn them out more and the car started to run alot better at around 3 and3/8ths turn for both mixture screws and the idle went back to specs at 750 rpm