We've taken a very simple topic and made it a LOT more complicated than it needs to be.
For 99 percent of the hobbyists who have decided to build, tune, and calibrate their Q-jet, baseplate rebuilding is an important part of the process, no doubt about it.
What MUST happen is that the person doing the work takes steps to insure that the HUGE secondary throttle plates are correctly adjusted to fully close and not allow air past them or a vacuum leak at idle.
They follow suit by adjusting the primary plates for full closing and making sure that bushings are installed if/as needed, plus tweaking the shaft if it is bent or twisted.
The linkage on the primary shaft can be incorrectly set-up on a stock carb as they were mass produced items. Matter of fact it's pretty rare to see one that will fully close and when move to WOT has the secondary throttle plate fully open as well, let alone all the throttle plates fully open simultaneously.
This is where the builder needs to pay close attention to detail starting with indexing, centering all the throttle plates for full closing. Then move on to adjusting the linkage so they fully open. Some models have provisions for a stop so the secondaries don't roll over past center, others do not.
You will also find more times than not the primary throttle plates are either over or under center when the seondaries reach the full open point, hence the need for adjustments in a few areas to make sure all these things are happening as they should.
Good results come from close attention to detail. I use and recommend a positive stop IF it is available, and nothing wrong with modifying things or making one when it's not.
As far as adjusting the open point or angle of the primary throttle shaft when it starts to open the secondaries, it's just not a main priority vs having everything else set-up as it needs to be. As the driver of your vehicle you should at this point in your learning curve know how to mash your right foot down hard and fast enough to get the secondaries on line if/when they need to be.
When I build or restore a Q-jet here, or any other type of carb I spend a LOT of time with the baseplate. Often machining it flat on both sides, installing bronze bushings, indexing/centering all throttle plates for full closing with the absolute MINIMUM amount of light showing, etc.
Time spend in each area of the build, being meticulous and close attention to detail is what sets your build apart from the rest and another important part of making sure that you get a good end result........Cliff
