Carb tuning can often involve expensive gauges that read things such as fuel to air mixture and exhaust gas temperature, but are these really necessary to adequately tune your carburetor? Of course not, in fact you can do most of the tuning on your carburetor cheaply and with the use of a few tools that you probably already have on hand. Your most indispensable tool will probably be a simple flathead screwdriver. With your screwdriver in hand here is how you can quickly and cheaply tune your carburetor.
Sometimes, possibly due to overuse or to old age, the carburetor may stop working properly. Or they just want to make their car’s performance better. At this point, tuning carbs can increase the carburetor’s optimal performance. While your standard carburetor may only have one or two tuning points, there are fancier ones that can have several different tuning points. Such as four-corner idle adjustments, replaceable jets, replaceable air bleeds, secondary idle speed screws and more.
Before you even begin tuning the carburetor, it is important to make sure the rest of the engine is in good working order. All of the valves should be adjusted. The filters should all be clean. Make sure your throttle linkage is in good working order and the distributor timing is correct. If these items are not in good working order then you may want to think about rebuilding the carburetor, as tuning may be difficult.
If you wish to allow more or less fuel into the carburetor, you can adjust the idle mixture screw. By adjusting the air fuel mixture in your carburetor, you can make sure you get good mileage. You will need to go to the air filter and unscrew the wing nut and then remove the filter. It is not necessary to disconnect any of the hoses connected to the filter.
You want to look at the section of the air filter that is screwed in the carburetor—particularly the screws on the lower part towards the front. You want to tighten these until they are completely tight and then loosen each screw slightly. Now you can replace the filter and start the car. You can tighten and loosen these screws as necessary.
Often times you may experience some idle problems that cannot be solved by a simple adjustment of the idle screws. Adjusting the idle feed restriction changes the size of the opening that is being restricted, potentially curing any idling problems you were experiencing. Changing the idle feed will almost certainly require you to adjust your idle mixture screws as well. This is a simple adjustment that can be done with the tools you have on hand.
If you are still experiencing idle problems you can adjust the air bleed. The idle air-bleed draws air into the engine to emulsify the fuel and air mixture. Opening the bleed allows for more air, while closing it allows for less and like the idle feed restriction this can change your idle circuit in your car.
The main jet restricts the amount of fuel that is dumped into the main metering circuit of the vehicle. Opening the jet increases the amount fuel infiltration, while closing it will allow less fuel into the car and this change can be made with the typical tools. Working on the jets is a somewhat more complex adjustment to the carburetor.
Don’t ever turn the primary float bowl to secondary. Don’t turn the secondary bowl into primary either. That will basically screw up the levels of your carburetor. The secondary is usually lower, in order to keep the carburetor fuel from spilling when you are pushing on the brakes too much. Gasoline overflow is also dependent on the internal pressure. In order to do tuning carbs successfully, the pressure must be around 4 PSI to 7 PSI.
If the carburetor is dripping with fuel and the gasoline level is spilling, this is not as much a problem of the float level but of the seat assembly and needle. At this point, no amount of carburetor tuning can really help. There is nothing much you can do but totally replace the carburetor itself.