lets wrap it up.
first the accelerator pump. note the mounting hole on the throttle shaft,and the upper adjusting nut arrangment.
note the dash and mark that must align when installed.use the nut on the link to adjust.
now onto the choke adjustments.note how the choke pull-off linkage attaches to the carb and pull-off diaphragm. starting with INITIAL CHOKE PLATE CLEARANCE.
with the electric choke cap installed,rotated to the rich (closed) side,open and close the throttle to set the choke.the choke plate will snap shut,and the fast idle cam will be on the top step,meaning,the screw with the spring will be sitting on the biggest step on the black fast idle camas shown. that screw is also what sets the fast idle rpms,which you will do after the carb is on the engine.
hook a vacuum pump to the choke pull-off diaphragm.and apply full vacuum,the diaphagm will pull back,opening the choke a bit as it does..
using a drill bit or allen wrench,and the measurment given in the manual for your vehicle year,measure the choke plate lower edge clearance,between the plate and carb body. use the 1/4" screw on the back of the pull-off diaphragm to adjust this measurment. i used the '75 spec of .166",and used an allen wrench that was close in size.
next,release the vacuum.put the fast idle cam on the second step,up against the shoulder of the high step. measure the choke plate clearance again,as above,but with no vacuum apllied. this is the FAST IDLE CAM ADJUSTMENT. this will be a smaller measurment than the initial clearance.
this is the fast idle cam adjusting screw.this will adjust the choke plate clearance for this setting. again,i used the '75 spec,.147",and a allen wrench that was close in size.
next,open the throttle to set the choke. apply vacuum to simulate a running engine. bump the throttle open and closed.the fast idle cam should go from the top step to the second step.
carb is ready for install and tuning,starting with fast idle speed,regular idle speed,then idle mixture via vacuum guage.
now,if when you are done,the truck starts,then fizzles out and dies,the initial choke clearance is too great,meaning the pull-off diaphragm is pulling the choke plate open too far.use the adjusting screw to remedy it,a little at a time,untill the truck stays running after startup. likewise,if the truck blubbers and chokes on gas after start up,the choke needs to be further opened by the pull-off.