Choose Your Quadrajet Number Identification Guide
Click here to enter them directly into your cart. Before we get started, we will assume the engine is in good condition and the entire ignition system and ignition curve is dialed in. Yes, add this item No, dating view my current items.
Would you like to replace your oldest item in the compare list? It is useful even if you don't own a Q-Jet. Free Shipping Order this item and get free delivery and handling on your entire order!
With your foot on the brake pedal, check to make sure the engine idles comfortably in gear. Beat-a-Price Guarantee Details. The primary wall of the cfm unit does not have this bulge, and is consistent throughout.
Never miss a sale on new parts, tools, and more! The secondary metering jets are fixed so the variables to experiment with are the metering rods, the hanger, and the secondary opening rate. Offer excludes truck freight and oversize fees. The rods are positioned by a hanger that moves with the primary metering piston that is pulled by engine vacuum.
On built Carbs they are on the round tag. This short tuning reference has only just scratched the surface of what you can do with a Q-jet. All Quadrajet fuel inlets are in one of two positions.
Choose Your Quadrajet Number Identification Guide
Very early Quadrajets had tags installed into a cast round area on the drivers side of the main body. Carburetors are often blamed for problems that are caused by ignition system issues. The last two remaining digits determine whether the carburetor came from a car equipped with an automatic or manual transmission. Any and all replacement parts between Carter and Rochester are directly interchangeable. If you're a Poncho Head, you know Cliff.
You can use it for reference. Usually an even number will indicate an automatic car, while odd numbers indicate a manual transmission. Later, electric chokes started showing up in certain applications to replace the hot-air-style chokes. The smaller primaries act as a small two-barrel carburetor until the accelerator is pressed far enough to open the secondaries. Finding a compatible donor carburetor for your application should be relatively simple.
If the time is longer, do the opposite of our first change and test again. Underneath that piston is a spring. For the most part, even numbers were used on automatic transmissions, and odd numbers on manual transmissions, but there were numerous exceptions. Have a carburetor problem you can't solve?
There are a countless numbers of Quadrajet carburetors still being used, or just waiting for you to rescue them from the local salvage yard. The Quadrajet became an instant success. Every factory Rochester Quadrajet flows a minimum cfm, and there were a few units rated at cfm. One must keep in mind when dating carburetors that the year of production may not always be the same year as indicated by the carburetor number. These adjustments alone can keep you busy for weeks if you are serious about tuning your Q-jet.
Quadrajet Casting Number Chart
The large flat area on the main body just above the secondary throttle shaft has a series of numbers stamped into the casting. In fact, it could be an advantage to keeping the mixture somewhat on the lean side in that short amount of time the air valve is transitioning to full open. Remember, turning the idle mixtures screws in clockwise creates a smaller passage and a leaner idle mixture setting. The B hanger will pull the rods out the greatest distance, with the V hanger the least.
This reduces fuel flow, reducing the amount of fuel delivered. Most carburetors produced in and after about have the choke housing mounted on the carburetor. In these instances, the thermostatic coil, which is mounted on the passenger side of the main body, uses heated vacuum and is easily recognizable by its large, black adjust ment disc.
The variables are jet size, the power tip and taper on the metering rods, and the power valve spring tension. It is quite common to find much later production dates then what is indicated by the carburetor number. Chrome Firefox Safari Explorer Opera.
We promise not to use your email address for anything but exclusive updates from the Power Automedia Network. Already know the part number you need? Record the numbers and procedure in a tuning book. Then, make a secondary metering change and perform the test again. The thermo static coil is activated by hot air from the intake manifold exhaust crossover system via a heated tube.
Quadrajet Power Your One Stop Quadrajet Shop
The distance the metering rod tip travels in the jet is determined by the hanger. Carburetors built before mid, have a tag with the part number. Would You Like to Pick it up?
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Rochester was not able to keep up with production. Innovate Motorsports innovatemotorsports. Odd last digit, dating glamour but I can assure you it was not used with a manual transmission.
If both the leaner and richer runs resulted in slower times, then the original metering was the best tune. We'll send you the most interesting Chevy Hardcore articles, news, car features, and videos every week. Since this actually occurs when the carburetor is not properly tuned, it is an ill-conceived, derogatory name. There are several ways to meter primary fuel flow.
- This is why you should make small changes and evaluate them over multiple driving events before making your next change.
- Then they're specially calibrated and percent flow-bench tested to ensure performance, and made available at a budget price.
- Usually two or three letters and the date that the carburetor was produced.
- But, not all Quadrajet carburetors were built by Rochester.
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Vertical Navigation Horizontal Navigation. The best place to start for tuning would be to install the lightest power valve spring. Good advice comes from Cliff, but it's still free.
This is where a good wide-band oxygens sensor and a data logger could be very useful in setting up your Q-jet to be just right. They may be located with the stamped numbers. Now, online we can take a look at the secondary side of the Q-jet. One should always give a carburetor a close visual inspection.
This was most common in the models. Summit Racing has more payment options. When tuning an engine with an unknown ignition curve, start your tuning efforts with the ignition system first.
- These Quadrajets are difficult to modify for conventional use.
- There are many other exceptions.
- Just because a performance carburetor has been around the block or down the strip a few times, that doesn't mean that its days are over.
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