I have holly 4-b and it seems when in drive the rpms drop below 500 and acts like it is going to stall. I have tried to adjust but it seems I can not get it to adjust right. idle mix screws seems to only drop the rpms. In park the rpms go to about 750 and seems to be idleing to high. Any help would be great.

 

well it should drop the rpms when you put it in gear 750 isnt all that bad try adjusting the idle speed in drive, thats how i do it in my camaro it idles around 550-600 in drive but idles about 700 or so in park. and do you have a big cam in your car.

 

Have you checked your float bowl level through the sight plugs to know if your fuel is at the right height?

 

I have not check the sight plugs. I am not sure what cam in the car. It idles at 750 800 in park when you put in drive it drops to 500 to just under. When I got it it had a new 305 long block in it. thanks for the help anymore ideas would help also

 

vacuum advance hooked up?