What looks good may in fact be the exact opposite of what the carb needs, and without knowing what is happening as you make changes, the results can be worse than if you had done nothing at all, so if you decide to do anything, do not change the shapes, angles of attack, or any other parameter that was a designed-in feature of the carb. The setting procedures will be for a Quadrajet 4-barrel- but they are basically the same for the Rochester Dualjet 2-barrel as well, which is the primary side of a Q-jet carb, anyway. These two changes seemed to cure the bogging. Due to the small size of the primaries and effort required to change primary jetting, and the relatively small effect it would have on performance, it's usually not worth fooling with unless there is a severe lean condition. This seemed to work fairly well in cool weather, but as soon as it started warming up, I started having problems.
But then again, being the type of person I am, I could be tearng this carb apart tomorrow just to see what if. Turn the screw back out until the highest rpm is achieved and then set the idle speed with the throttle screw. Primary side main fuel metering begins off-idle and goes through wide-open throttle. Caution: Do not overtighten any vacuum fitting or plug into the baseplate! The later carbs will also have very small idle fuel supply holes in the baseplate. Hope the info helps some. Cliff is the guy who has built up the qjet's for Jim Hand's winning Pontiac drag cars.
It seems like a lot of work but if you can find a section of isolated road. It is sort of like installing bigger jets because primary rods get smaller the farther up they are held. Re: Adjusting Rochester Quadrajet secondary--Update-- Check out the Q-jet articles on this website. It seems like a lot of work but if you can find a section of isolated road. By the way, the proceedure in the Clymers was exactly the same as someone posted for me from the manual.
The arm usually, it's a greenish piece of metal is held in place by a press-in fitting that must be eased out partially not all the way! Cold engines need a leaner fuel mixture to run smoothly. Our 73 Grandville bogs badly, and I was hesitant to tear into it- until this. When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. As soon as the throttle is moved toward open, the tab on the throttle allows the choke to close. As you adjust you will notice the engine increase in smoothness and speed. Another highly reviewed title is by Doug Roe. I have the rebuilt carbon it and I cant remember what the setting on the rear choke plate is.
There is an adjustment on the tension spring for the butterflies. . The pump should start pumping at about 10 percent throttle open. Become familiar with the camera you have and use it to photograph everything, from every angle, every step of the way. The choke linkage has several parts that must line up in a specific way during re-assembly or they will not work.
How much wear is too much? Understanding how a carburetor functions will enhance your tuning and troubleshooting skills. Don't know the exact percentage but they need to start opening around that 50% mark because from that point on the secondaries need to catch up so that they both reach 100% together. This looks a little intimidating but it's not difficult, if you are patient and careful. There is much more to adjusting a Q-Jet than angle of throttle plates. There was a mod in the rebuild kit which included a large rubber block which provides a seal for these drilling ports.
It can be carefully bent to set the opening amount. During normal driving the primary barrels are adequate for cruising speeds. Article remains under construction as of June 22, 2011. And with those small primaries, a 750 cfm Q-jet can work very well even on a tiny small-block like a 305 or even a 283. Give it no more than half a turn clockwise, adjusting it just until your engine idles smoothly. Wiki articles and Hotrodders Knowledge Base links Wiki article intended to provide information on rebuilding a carburetor.
This will increase your emission levels. In the future, as time allows for updates, the article will cite sections and passages from related books to help the reader follow along with ease. There is a moment of quiet followed by a large increase in exhaust volume, sometimes described as a 'booming' noise. The carburetor is held in place by two long bolts visible on top of the air horn and either two nuts or two bolts on the back of the carburetor on top of the throttle cable bracket. The advantage of the Q-jet is its small primary throttle venturis with very quick-responding boosters that offer excellent throttle response, making it an excellent street carburetor.
I have fixed, for the most part, the bogging. And when you upload your pictures, be sure to organize them into folders and sub-folders with useful categories for titles, i. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. Epoxy will eventually delaminate from the metal and the leak will resume. Another benefit is that they are 800cfm and work very well on large cid engines.
The use of latex gloves and a full-sleeved shirt is highly recommended when working with this chemical. This engine performs as good as could be expected, except possible slight improvement in fuel efficiency, but at this point, probably negligible. By 90 degrees I'm talking about the rear portion of the flap, the front will go past 90 degrees on a correctlyset up carb. Boat Design Net does not necessarily endorse nor share the view of each individual post. Carburetor Circuits Engine speed, load, and starting demands each dictate how fuel will be delivered. Video series by on Gives a detailed, step-by-step demonstration of disassembling and rebuild a Quadrajet carburetor. The well plug stop-leak pads that come in many rebuild kits are a joke below, center and right.