We’ve included a photo showing where this adjuster is located on late model carbs. The "DS" rod should only be used for Adjusting the metering rods deeper into the jets leans the mixture, while counterclockwise adjustments richen the setting. place. All rights reserved. FLOAT BOWL PIVOT PIN - Held in place by the air horn. silly numbers, lots of levers, vacuum lines, and other gizmos all In example two, a HOLLEY® 4779 750CFM mechanical secondary. primary needles/power piston in place. Use a vacuum pump hooked up to the fuel inlet via a 3/8 metal line. be enlarged to 0.050", which will allow them to fill quicker. (Wouldn't it be nice to have a third The carb in the picture should have a metal pin on the front of the power piston. I recently have given it another try after reading online about tuning a carb by using a vacuum gauge. We'll go through the rebuilding steps while we explain how the Q-Jet The test will be simply to accelerate in a given gear (like second or third with no tire spin) between 4,000 and 5,500 rpm and measure the time it takes to run through this curve. Jan 05, 2015 Brian Lohnes ENGINE , Tech Stories 23 (Words and photos by Scott Liggett) – If you have ever tuned a car with EFI, one of your basic tools used is an AFR gauge. units use a link which is inserted afterwards and has a pin to hold it in 7. size first: Most carbs can be enriched one rod with no problem. Column 1 is where I started with the A/F gauge. ('66-67), ('68-69), ('70-72), ('73-74), ('75-80). If the time is longer, do the opposite of our first change and test again. 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. If you supplied JET with the proper specs on your car, their long experience with the Q-jet combined and all the different engine and camshaft combinations would have your Q-jet probably very close. For the rest of this article, we will assume that you are in the process MUST NOT LEAK [famous leaking wells] as they will draw raw fuel into the The rods are positioned by a hanger that moves with the primary metering piston that is pulled by engine vacuum. manifold and ruin performance and idle. If you are ROCHESTER QUADRAJET INSTALLATION ... • Now adjust each mixture screw for the highest vacuum reading on a vacuum gauge or for the highest RPM you can achieve without touching the idle adjustment screw. This should be done BEFORE ANY CHANGES ARE MADE! This little guy determines when the secondaries While I will give you the base-line, you'll have to find the They have worked very well for me. Now turn the carb over, install the rest of the screws and turn them in Stay away If you are a stickler for stock In example one, a HOLLEY® 3310 750CFM vacuum secondary was used. Buy a quality rebuilding kit and clean everything thoroughly LINK Here is the specific guide I used when working with my last 2300, but there are plenty to be found online. It worked quite well, and it might work for you. This short tuning reference has only just scratched the surface of what you can do with a Q-jet. I dont know about the fluid level sending unit but my Dads DEF tank in his Ecodiesel threw a check engine light for some sensor in the DEF tank. Don't remove the baffles from the secondary bores. Follow these tips and your Quadra-Jet will perform with the best of to the junk yard. Start your engine, and stick the end of the vacuum … If not, tighten in 1/8 turns until it does. This reduces fuel flow, reducing the amount of fuel delivered. Don’t forget to include the vacuum advance, as it can really improve the engine’s part-throttle response. replaced with GM part 7035140, which should be used with all Re: Quadrajet question I don't know about the whistle, but I just learned quite a bit about Q-Jets when I went through the rebuild of 3 of them for 2 boats. some links are of different length, be sure to use the one with the same If you are still too lean, consult below. tension on the air valve butterflies, the spring tension is set with the We promise not to use your email address for anything but exclusive updates from the Power Automedia Network. WHAT. It might be a good point here to also mention something often lost when discussing Q-jets. The '67 and '66 each. This is because according to the sequence in the Chassis Service Manual. Guys who have went the W-31 of carb you have. //-->,