Quadrajet
(→Choosing a carb) |
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You need to pay attention to a few important things when choosing a carb to rebuild/use on your engine: | You need to pay attention to a few important things when choosing a carb to rebuild/use on your engine: | ||
| − | *Fuel inlet (straight or 90º), so it doesn't interfere with any of the accessories or water neck, etc. 90º fuel inlets are usually exclusive to Chevrolet (small block V8, V6-90 (1985/86 and marine/industrial), 1968-85 Cadillac V8 (472, 500, 425, 368), and 1983-89 Mopar LA V8s (Dodge Ram truck and van applications are non computer controlled while the passenger cars (M platform) had electronic controls). | + | *Fuel inlet (straight or 90º), so it doesn't interfere with any of the accessories or water neck, etc. 90º fuel inlets are usually exclusive to Chevrolet (small block V8, V6-90 (1985/'86 and marine/industrial), 1968-'85 Cadillac V8 (472, 500, 425, 368), and 1983-'89 Mopar LA V8s (Dodge Ram truck and van applications are non computer controlled while the passenger cars (M platform) had electronic controls). |
*Choke type. Most prefer an electric. A hot air type choke can be converted to electric easily. A divorced choke Q-jet is able to be converted to electric, however the kit is rather expensive. | *Choke type. Most prefer an electric. A hot air type choke can be converted to electric easily. A divorced choke Q-jet is able to be converted to electric, however the kit is rather expensive. | ||
*Whenever possible, get the factory cable bracket. Even if you're using an aftermarket intake, it might come in handy for making up your own bracket. And regardless if using an aftermarket intake or not, the bracket can be used to measure the correct cable/carb relationship for setting up whatever bracket that's used. | *Whenever possible, get the factory cable bracket. Even if you're using an aftermarket intake, it might come in handy for making up your own bracket. And regardless if using an aftermarket intake or not, the bracket can be used to measure the correct cable/carb relationship for setting up whatever bracket that's used. | ||
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1976-up carbs are often preferred due to less wear than the older carbs, often an integrated choke assembly (hot air or electric) will be present, and the float and needle and seat assembly setup is better. Also because there were improvements made throughout the run of Q-jets, newer is better. The '76-up carbs will also have APT (adjustable part throttle, a way to fine tune the carb). | 1976-up carbs are often preferred due to less wear than the older carbs, often an integrated choke assembly (hot air or electric) will be present, and the float and needle and seat assembly setup is better. Also because there were improvements made throughout the run of Q-jets, newer is better. The '76-up carbs will also have APT (adjustable part throttle, a way to fine tune the carb). | ||
| − | Cars (not necessarily trucks/vans) from '81-up are going to have feedback carbs. No good for anything other than computer use (CCC), or possibly as an all-out race carb where it is set up/jetted to run without primary metering rods. Some 1985/86 Chevrolet/GMC trucks and vans with the base 305 will have a dual | + | Cars (not necessarily trucks/vans) from '81-up are going to have feedback carbs. No good for anything other than computer use (CCC), or possibly as an all-out race carb where it is set up/jetted to run without primary metering rods. Some 1985/'86 Chevrolet/GMC trucks and vans with the base 305 will have a dual capacity accelerator pump assembly (which resembles the feedback carb used in passenger cars). These carbs are often overlooked for performance use. However, they can be readily utilized once they are understood. More on them can be found at the link located at the end of this section. |
| − | Interestingly, one of the best/easiest way to find a good carb | + | Interestingly, one of the best/easiest way to find a good carb is to look for one off of a truck or van. Up until 1986 truck carbs were often non feedback (not an "electronic" carb), and they were nearly all 800 cfm units- even those found on 4.3L V6 engines! These engines can also have the large coil-in-cap, non-feedback HEI distributors. |
It's also a good idea to acquaint yourself with the [http://www.crankshaftcoalition.com/wiki/Q-jet_with_dual_capacity_accelerator_pump '''"dual capacity" accelerator pump Q-jets'''], in case you run across one. They can make a good performance carb. | It's also a good idea to acquaint yourself with the [http://www.crankshaftcoalition.com/wiki/Q-jet_with_dual_capacity_accelerator_pump '''"dual capacity" accelerator pump Q-jets'''], in case you run across one. They can make a good performance carb. | ||
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