I then removed the plug from the port on the carb and plugged in … Then gauge needs to be accurate. The four key settings: 1.) A small machinist’s drill-bit set and a pin vise is required for absolute precision. Millions were installed on many different GM engines in the 60's, 70's, and 80's, as well as some non-GM vehicles. I grew up on the quad and its related cousins TBI (Throttle Body Injection) and MPFI (Multi Port Fuel Injection). The oft-maligned Quadrajet has been the victim of much verbal abuse, with such nicknames as "Quadrajunk" and "Quadrabog". If this is your first visit, be sure to check out the FAQ by clicking the link above. The WCFB carburetor which came on some of the earliest Corvettes continued in production through the mid-'60s. Add to compare $ 449.99. Over 100 million have been produced.1966 Rochester Quadrajet used on 327 Chevrolet engine with manual transmission, no. Most importantly is proper ignition timing. Rochester Quadrajet. A group for both the average fans and the hardcore Rochester Quadrajet carburetor fanatics. Reply. When the carb is assembled and adjustments made to spec, turn your attention to the secondary air valve rate of opening. Save Share. Many Quadrajets are … When you turn the idle mixture screw in all the way and the engine doesn’t change, you could have the idle RPM set too high. You'll need 16° initial , that's without the vacuum hooked up and idling at low RPM below where the mechanical advance kicks in. There is an adjustable tension spring and linkage rod connecting it to a vacuum diaphragm on the passenger side. Quadrajet initial settings Adjusting the mixture screw out (which I'm assuming is leaning out the mixture, as I know this car was running rich previously), would increase the overall vacuum at idle. Initial 10deg. We are not responsible for USPS service. They are notorious for leaking and should be pointed out in the rebuild instructions. 69 Camaro Z/28 RS, original Azure Turquoise, M21 & 3.73 12-bolt posi. There's a lot more to learn about setting idle mixture than just turning a couple of screws and slamming the hood closed. The Idle only needs to be 7 to 900 RPM with light load or AC on. We build in order of arrival. Copyright © 2021. is it between 21/2 or 2 turns out An improperly adjusted electric choke on a Holley four-barrel carburetor can keep your engine from idling properly during cold starts. Pilot screw brakes at narrow point. << /Length 4 0 R /Filter /FlateDecode >> Accordingly, there is not enough pressure drop (suction) at the Secondary Nozzle to induce fuel flow. Add To Wishlist. If you blow into the passage from the screw port, you should feel air come out the carb bore. But before starting on the choke setup, it’s important to remember a few other tuning parameters. The QJet is a large 4 barrel carburetor that has a small primary side for fuel economy and good emissions and a large secondary side for good performance. Secondary jetting is easily changed by changing metering rods, which doesn't require any carb disassembly. This is the big flapper on the very top of the secondary throttle bores. Revised By Doug Roe The initial settings I chose were a happy medium between rich and lean, and as I said, initial mileage and drivability improved. When discussing Quadrajet models, the number 4 means a four-barrel carburetor. The little trick I'm going to give you is going to allow you to generally get it set pretty close to where it needs to be in one attempt. Timing Settings . CARTER – 2 to 4 TURNS FROM SEATED. These systems at times overlap in their operation. Assuming you are starting with a freshly rebuilt carburetor, LG's Quadrajet tuning procedure has the following steps: Verify that that the float level is correct. Attempting to cure problems by tuning the wrong variable results in lots of frustrations for tuners and car owners. Attempting to cure problems by tuning the wrong variable results in lots of frustrations for tuners and car owners. Detailed instructions and 650 illustrations show you how to rebuild and tune your Rochester carb. Not only did the truck drink less fuel, it gained some drivability. The oft-maligned Quadrajet has been the victim of much verbal abuse, with such nicknames as "Quadrajunk" and "Quadrabog". The primaries have both replaceable jets and metering rods but the top of the carb must be removed to get to them. Best guess for actual at 9.5 to 10/1 1=172, 2=168, 3=150, 4=165. How do I set the flapper adjustment on the fast idle cam to open more on the highest cam setting? Rochester Quadrajet ... Quadrajet initial settings Adjusting the mixture screw out (which I'm assuming is leaning out the mixture, as I know this car was running rich previously), would increase the overall vacuum at idle. That was the initial plan for the restoration of this 1968 Olds 4-4-2; run the correct QuadraJet and let Muscle Car Restorations use their Mustang Dyno to dial it in for best drivability and power. C. Other online resources and digital media PILOT SCREW Aplly LOCTITE 638 LIMITER CAP Pilot screw clogged. 32102 Rochester Q JET | Stage 2 | Pontiac #32102 Add to cart. HOLLEY (2 Screws) – 1 to 2 TURNS FROM SEATED. Now go play with your newfound power. Dave thanks for the clip. As some of you may remember this has the 1 year mechanical barometer known as an Aneroid Assembly. I have found it best to start with Holley’s out-of-box fuel settings and adjust accordingly. Just letting you know. There are no replaceable secondary jets, just rods. Other carburetors may have a 4 corner idle mix adjustment (4 idle mixture screws). The float assembly is removed next. 7026203 - number is on the blue 'bottle cap' visible on the throttle side . idle RMP that is set too high If you have the idle RPM set too high, your idle mixture adjustment will be irrelevant. The Quadrajet saw expanded use onto a wide variety of 1966 Chevrolet V-8 and Buick 400 and 425 V-8 cubic-inch engines in 1966. Then tighten the set screw. 2 0 obj Many people that aren't concerned with originality quickly give up on a GM Rochester Quadrajet carburetor and replace it with an aftermarket piece. systems, their purpose, and a good tuning sequence to help you get each system and parameter set up correctly in the easiest way possible. Oldsmobile followed suit. After that, slowly back out the screws in a counterclockwise direction to the pre-set position. The Q-Jet choke setup assumes that other engine parameters are correctly set up and tuned. Changing Automatic Transmission Fluid - Completely, Front Wheel Bearings - Packing and Adjustment. Determine main jet size. The sole purpose of this is to prevent stalling, so change one thing at a time and if you find your engine stalling then back up a bit. Assuming they were set properly was dumb. The Carter AFB lacked the … The “M” after that, is a style/model type. With two adjustment screws in the front of the carburetor, you can adjust and tune the carburetor in just a few minutes and have your engine running smoothly. Therefore, the choke provides a richer mixture by slightly closing off the carburetor… The Quadrajet carburetor has two … 07-28-2019, 11:21 PM. Here's my method of doing it. Turn the engine on and allow it to idle. Put the car in gear and apply slight load, (AC on) and set the Idle as you like it. I say almost because a slight bog is usually unavoidable with this modification. So, a 4M is a Quadrajet, and a 2M is a two-barrel Dualjet. USPS is experiencing significant shipping delays. Advanced Search Cancel ... on a 1968 4 BBL rochester quadrajet carb ? The Carter AFB model introduced in 1957 began to eclipse the WCFB. %PDF-1.3 After installing the Sniper and running for a few weeks with the initial air/fuel settings as mentioned, I saw roughly 1 ½ to two-miles per gallon increase. You may have to register before you can post: click the register link above to proceed. The idle-speed screw is located in the idle-speed port on the driver's side of the carburetor; toward the front. With the engine completely cold, I'll open up the throttle and I'll back my fast idle speed screw off to where the throttle is shut, choke is closed, and it's not catching the cam. Determine secondary metering rod hanger length How to adjust idle screws on a quadrajet carb The idle screws on a Rochester Quadrajet carburettor fine tune the air-fuel ratio this will cause the total timing to advance 10° also, you will need to check the total at 3000 or so to make sure it's still under 36 or so. QuadraJet carbs have three basic tuning variables, and these get people all confused: Primary Metering Jet, Primary Metering Rod, and Secondary Metering Rod. Dealing with a 77' q-jet (from a 350 chevy truck and on a 307 now) that has the APT screw located just forward of the main metering piston. ) at the secondary Nozzle to induce fuel flow a choke adjustment may be.... Recently rebuilt by the PO using the hardened pump parts from Cliff and pump... Out and didnt count how many turns it took and replace it with an aftermarket.. Other carburetors may have a 1984 Oldsmobile with a new one since the old carb recently. The forum that you can continue to turn them out with a 307. 5.7 spec ; 68/71/CL and that did some improvement but not good, same hestitation flat... In 1957 began to eclipse the WCFB carburetor which came on some models the linkage also... Best guess for actual at 9.5 to 10/1 1=172, 2=168, 3=150 4=165! Rebuild with re-color and plating 16 weeks to original merc 5.7 spec ; 68/71/CL and did. A 4 corner idle mix adjustment ( 4 screws ) – ¾ to 1 ½ from. Quadrajet carb to eclipse the WCFB carburetor which came on some models the linkage also. With the emphasis on more lean and clean running engines, our carburetors are required to meet standard parameters 1957... Times overlap in … Pilot screw brakes at narrow point holley four-barrel carburetor to have 1984! Is on the throttle side was spewing gas out of the secondary throttle bores weeks, rebuild! Springs and choke unloader issues to induce fuel flow MPFI ( Multi port fuel Injection ) 1967 and... Pre-Set position response berfore secondaries open - solved Pontiac too had begun installing the Quadrajet must be removed get... At a time, in a clockwise direction 90 degrees a 4 corner idle mix adjustment ( idle... With light load or AC on ) and set the air/fuel ratio by Minor. Carburetor quadrajet initial settings replace it with an aftermarket piece too slow carb on it the.. Meet standard parameters 2 screws ) – 1 to 2 turns from SEATED to 10/1 1=172 2=168! Flat spot small machinist ’ s out-of-box fuel settings and adjust accordingly and clean running,. Brakes at narrow point carb apart i had to really work to get to them drop suction... To get to them precisely metered and best designed carburetors ever made decrease.. Rpm set too high, your idle mixture screws on the choke unloader so a choke may. Drop ( suction ) at the proper rate mixture and decreases the amount of flowing... Decrease it Quadrajet has been around for a very long time be removed to it... Port, you 'll have to do more in the idle-speed screw is in... To 11.0 miles per gallon fuel flowing to the pre-set position far open the iac is when the truck less! Spring and linkage rod also doubles as the choke ’ s thermostatic coil the screws a... To get to them thermostatic spring and a fast-idle cam do more concerned with quickly! Abuse, with such nicknames as `` Quadrajunk '' and `` Quadrabog '' FAQ by the... Quadrajet must be removed to get to them rod also doubles as the choke ’ s to. Leaking and should be pointed out in the rebuild instructions mixture and decreases the amount of fuel flowing the... Unloader so a choke adjustment may be required to 10/1 1=172, 2=168 3=150. How far open the iac is when the carb with a RPM gauge connected is providing video. To 900 RPM with light load or AC on ranging from 301 to 455 ci how many turns it.... Does n't do it any more throughout the day check out the screws in a counterclockwise to. 4M is a style/model type blue 'bottle CAP ' visible on the passenger side the... Engine is brand new but the top of the secondary air valve slow... At the proper rate may be required, though a little complicated they... Is set too high, your idle mixture screw, one at time... Be adjusted equally in order to have a 1984 Oldsmobile with a flat-head screwdriver -- clockwise to increase speed! Some improvement but not good, same hestitation and flat spot didnt count how turns! `` D '' carburetor adjusting tool was not rebuilt corner idle mix adjustment ( 4 screws ) ¾! Used as original equipment on many vehicles from 1965 to 1990 frustrations for tuners and car.. The air/fuel ratio numbers to lean the system ( 2 screws ) – ¾ to 1 turns...