I was tuning the idle mixture screws today and noticed that when I did the drivers side, as I turned the screw in, the rpm increased. When I did the passenger side, the car wanted to stall as I turned it all the way in. What would make it do this? The carb is an Edelbrock Thunder 650. I just installed Rhoads V-Max Super lube lifters and before that, the carb functioned normally. Turn the screws in, engine stumbles. Turn them out, engine smooths out. The engine has 16hg of vacuum and idles very steadily at 800rpm in park/neutral, and rock steady at 650rpm in drive. I run a Canton Racing 1/2" phenolic spacer for heat soak(Edel's seem to be terrible for this) and it's the four hole type. I used to run an open hole gasket both under the spacer and under the carb, until I was told that the gasket directly under the carb and on top of the spacer should be a 4 hole like the spacer, or it would negate the function of the spacer. The car has plenty of power and runs great. Any help would be greatly appreciated.

Are you saying you can turn the drivers side all the way in and it never starts to stall? If so that side of your carb is getting air from someplace it shouldn't be.

If you can eventually get it to start to stumble I would verify how many turns each screw is out. With the engine shut off count (use the screwdriver slot to visually count 1/2, 1/4, 1/8 and even 1/16 of a turn) the turns as you close the screws down. Don't tighten them down, stop when you meet resistance. Compare the 2 totals to see if the driver side is just out a lot further than the passenger side.

From here adjust them back out using the side with the least number of turns out as your start for both sides. Start the engine and when it's warmed up tune from there but keep track of the changes and split the difference to make both screws adjusted the same.

I just tried it again and it worked fine this time. Apparently when I had the carb off for something else, I knocked it over. Maybe that had something to do with it. I also removed the idle mixture screw on that side and re-installed it. It all works fine now. Thanks.