""There is a spring with a bolt going through on it clearly allowing for adjustment what would adjusting that smaller or larger do?""
- This adjustment is so that you can readjust the clearance when you swap in different size pump cams (black, pink, white, red, orange, green and blue). Each cam has a different profile and each one needs to be adjusted just like you already have done.
- The air bleeds control how much extra "air" comes into each circuit. Think of the air bleeds as an "external" adjustment. The Idle Air Bleeds are an external adjustment for the Idle Feed Restrictors which are on the metering blocks. The High Speed Air Bleeds (Main Air Bleeds) are an external adjustment for the jets. If you have three sets of each, then you have three adjustments that you can make on the outside of the carb before having to take the carb apart for the internal adjustment (IFRs and jets).
Both of these sets of bleeds are on the top of the carb. The IABs are the outer four and the HSABs are the inside four. It is much easier to see what each one will affect if you have an A/F tuning kit. Without the kit, you are going on feel and sound alone.
- IFRs, metering screws, and IABs affect the idle and the cruising up to around 50-55mph or so pending on rpm.
- Primary Jets and HSABs affect the cruising A/F from 50-55mph and on up.
- Power Valve and Power Valve Restricters control "when" (PV) and how much more fuel (PVCRs) once the vacuum is low enough to open the PV to help supply extra fuel to the main jets.
- Float levels will affect A/F from idle to WOT. This is an external adjustment that can be made that will affect the A/F from idle to WOT. This adjustment affects the entire range of the carb, not just certain circuits.
- Pump cams and squirters are the "band-aid" of the carb. They help fix hesitations during acceleration. If too much fuel is added per the pump cams and squirters, then this will hurt acceleration and cause black smoke.
- Secondary Jets and HSABs affect the WOT A/F.
Setting the metering screws at 1.5 turns out is only a base line for some brand named carbs. This should be rich enough to get you started up and then you need to tweak the idle vacuum and A/F from there. The metering screws on a Quick Fuel carb are generally set at 1/2 to 1 full turn outward. The main goal is to get the idle A/F ratio setup for a clean idle but rich enough to keep the vacuum up to produce a smooth idle especially on auto cars in D with the brake applied (like at a stop light).
Note: There are a few different circuits in the carb. They can all be rich or they can all be lean. One can be rich and then the others be lean. So saying the carb is rich is a very general statement. As you learn the adjustments on each circuit, then you can tune the appropriate circuit to fix the tuning issue.
Start with the idle circuit: IFRs, Metering Screws, and IABs. Once you have a clean idle, no hesitation off idle from a stop (light acceleration), and a clean cruising A/F, then you tune the accelerations off idle. This includes the pump cams and squirters. Once this is complete, then you test your main jets. Cruising from 50mph on up to 75mph or so is where you want to tune the main jets. You have the internal adjustment of the main jets and the external adjustment of the Primary HSABs. You may not be able to tune the HSABs without an A/F kit. Once this is complete, then tune the Power Valve and the PVCRs to allow a clean transition from cruise to the main jets. You can test this by cruising at a steady pace (50mph+) and then pushing down on the accel pedal (do not open the secondaries) and see how it reacts after the vacuum drops below your current PV rating. An A/F kit can show you how lean or rich you are once the vacuum drops down to and past the PV rating (5.5, 6.5, etc.). Then you can adjust the PV timing and the PVCRs size to keep you in a good A/F range. Then after all of that is done, then use your secondary jets for the WOT A/F tuning. Keep in mind that you have an internal adjustment (secondary jets) and you have an external adjustment (Secondary HSAB's) for tuning your WOT. If you have three sets of HSABs and you can not get the WOT A/F that you want, then open the carb and change the secondary jets. Then you start the process again.
Did you notice that I kept saying A/F kit! These are a remarkable tuning "tool" when you are working with a carb. There is a lot going on inside of a carb from idle to WOT. The A/F kit helps you see the changes in A/F while trying to tune.
Look at tuning a carb like standing at the bottom of a flight of stairs. One step at a time (idle) until you get to the top (WOT). Lets say there are 10 steps. If you make a tuning change to a lower step number, that change will affect all of the higher numbered steps (Total A/F).
If you tune step one (idle: IFRs) then you jump to step 10 (WOT: HSABs), you have no idea how the rest of the carb reacts. Or, if you tune steps 1 thru 5 in that order, then you change step 3, this change now affects steps 4,5,6,7,8,9,& 10. If you change step 9, then your change only affects step 10. If you change step 2, then your change affects steps 3 thru 10. This is why you tune a carb from step 1.
Learn how to adjust each step of the carb and take notes after each change! This will allow you to see how each change affected the issue.
Have fun!
