Set secondary air valve spring initial tension. The length of the non-metering portion of the metering rod was 2.01" and the length to the top of the power step was 2.026". 2. Since the primary jet is larger, I would need a larger diameter metering rod as well but only the following Edelbrock M-series rods are now available:  0.048" / PN1941, 0.050" / PN 1943, 0.052" / PN 1945, 0.054" / PN 1947. After much trial and error with choke adjustments and APT adjustments, I learned that both have a great effect on cold starts. Assuming you are starting with a freshly rebuilt carburetor, LG's Quadrajet tuning procedure has the following steps: The best way to determine the optimum jet diameter is on a chassis dynamometer. A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Using my digital vernier caliper, I measured the length of my 52K metering rods to be 2.41" and my jets to be approximately 0.087-0.088". Lars Grimsrud (LG) is very knowledgeable about Quadrajets and has a Quadrajet tuning paper that is available upon request. Specifications about my 750 CFM Quadrajet carburetor: The Quadrajet's primary venturis are in use at all times and it is crucial that the primary metering circuit is properly calibrated for all engines. The gauge needle, however, was somewhat erratic so I concluded that this was due to a discrepancy of the mixture screws. (if possible) 3. After replacing a rusty gas tank in 2015, I ran the AFB again to ensure that any residual rusty silt didn't settle out in my newly rebuilt Quadrajet. It’s an excellent way to maximize the performance of … IDLE MIXTURE SCREW LOCATIONS - (Q-JET, CARTER) The idle mixture screws are located on the bottom front of the carburetor. Spring is used on the curb idle speed adjustment screw. Only the newer M-series metering rods (ie, 48M, 49M, ... 55M - truck applications & Edelbrock Quadrajets) and the 50D have a tip diameter of 0.036" along with Edelbrock's . After raising the APT to 5½ turns, I felt that the engine had reached the practical limit of part-throttle enrichment so I used that as my APT adjustment starting point. The slower combustion rate can result in the fuel charge in the combustion chamber still burning when the exhaust valve opens, thereby causing burned exhaust valves. If turned out this far, the metering rods would be sitting very high out of the jet so that the economy fuel mixture would be fairly close to the power fuel mixture. I then turned out my APT 1/2 turn at a time and found that my idle speed kept increasing. The part throttle cruise section of the metering rod comes in a variety of diameters and tapers (transition between between lean and rich). Determine main jet size. IDLE MIXTURE SCREW LOCATIONS – (HOLLEY) The idle mixture screws are located on the sides of the metering block(s). 425. I'm just trying to find a "range" of mechanical adjustment for the curb idle screw that is between "too far open" and "won't run closed". Add to Cart. It's been doing its thing for 40 years on my '70 L48 350 Monte Carlo--forever known as … Sounds like you are trying to make it too lean @ idle thus having to have the plates open too far. Try manifold vac. Adjust the Idle Mixture Screws on both sides (one side if its a 1 barrel) OUT 3 1/2 turns. If my 52K metering rod was adjusted the bottom of its travel (ie a diameter of 0.046") and I needed more enrichment (252.3 E-5 in² flow area), the best M-series rod would be the 52M with a leanest flow area of 253.3 E-5 in². Les, thanks...I might email them to see what their bench setting is. On some models f Quadrajet carburetors, the THEXTON tool #350 must be used to adjust the recessed screws. Used Fast idle cam. I got the distributor through Mopar Performance (formerly Direct Connection) and it was used for performance (drag racing). First, check to make sure both idle mixture screws are adjusted equally. M-series (0.036" power tip) and P-series (0.026" power tip) have a 0.012" taper. It is used for idle speed setting and on fast idle screw. If the choke plate does not open enough, after startup the engine will load up, blow black smoke from the tailpipe(s) and possibly stall and flood. The HP and Ultra HP carburetors from Holley feature screw-in idle and high-speed air jets, which allow for emulsification tuning in various conditions. My first challenge after reinstalling the Quadrajet in November 2016 was hard starting in cold weather. Although the primary jets interchange between all years of manufacture, there was design change in 1975 and the primary metering rods from 1965-1974 (PNs starting with 70) are 0.080" longer than those from 1975-1980 (PNs starting with 170). Set the screw in the position where the engine’s idle sounds most even and smooth to … The idle mixture screws are located in the base plate for superior idle quality. Compared with the old Carter Strip Kit (metering rods & jets), jetting a Quadrajet is much simpler because all of the metering rods have the same tip (power setting) diameter (power setting) of 0.026". I know they're in the business to sell and fix carbs, not give out free advice, but you never know until you try, right. Does anyone have any suggestions on where to start with a Qjet idle speed screw? It is impossible to exchange early metering rods with late metering rods. sku: 55599. Sticking with the 52 metering rod, I have the following results for a variety of main jets: Besides having the quickest 0-60 time, the #73 jet also had the best seat of the pants feel. Set desired speed with the Idle speed screw. http://garage.grumpysperformance.com/index.php?threads/q-jet-info.1144/ http://garage.grumpysperformance.com/index.php?threads/looking-for-q-jet-index.7763/ http://www.route66hotrodhigh.com/PowerTuneQjet.html http://www.gmcmi.com/wp-content/uploads/2014/05/Quadrajet-Carb-Primary-Metering-Rods.pdf http://www.corvetteforum.com/forums/c3-tech-performance/1023501-updated-q-jet-listing-shows-available-parts.html, http://www.cliffshighperformance.com/ https://quadrajetparts.com/ http://www.edelbrock.com/automotive/mc/carburetors/access-q-jet.shtml http://jetchip.com/product-category/performance-carburetors/rochester-quadrajet/rochester-quadrajet-parts/, http://garage.grumpysperformance.com/index.php?threads/q-jet-info.1144/, http://garage.grumpysperformance.com/index.php?threads/looking-for-q-jet-index.7763/, http://www.route66hotrodhigh.com/PowerTuneQjet.html, http://www.gmcmi.com/wp-content/uploads/2014/05/Quadrajet-Carb-Primary-Metering-Rods.pdf, http://www.corvetteforum.com/forums/c3-tech-performance/1023501-updated-q-jet-listing-shows-available-parts.html, http://www.edelbrock.com/automotive/mc/carburetors/access-q-jet.shtml, http://jetchip.com/product-category/performance-carburetors/rochester-quadrajet/rochester-quadrajet-parts/, #52K - 0.052" [Single Taper (0.052 - 0.046) & Step]. One of GM's better ideas was to include a way to fine-tune the part-throttle fuel mixture with the Adjustable Part Throttle (APT). Buzzbom, you said "My initial timing is 20 degrees with vacuum on ported". The throttle idle screw is a slothead screw located on the driver’s side of the carburetor. Screw, fast idle and follower holding screw flat retainer $7.99. Determine secondary metering rod hanger length After some troubleshooting, I noticed that only my left (choke side) primary venturi was flowing any fuel and the right-side venturi was completely dry. Adjust as required. Next with the transmission in Park and a vacuum gauge hooked to read manifold vacuum, adjust the idle mixture screws in small increments until you can get the highest vacuum reading with the leanest idle … APT adjustment @ 3.5 turns, Secondaries locked out, transmission automatically shifting @ ~4500 RPM, 0-60 times reflect that this car has highway gears (2.76:1) and larger tires (P225/70R14) than stock (P185/75R-14), distributor PN 2444648 (distributor: 12° @ 2200 RPM centrifugal & 7° @ 13" Hg vacuum), total mechanical timing (initial + centrifugal) 30-32° BTDC, all in by ~3000 RPM, total advance (mechanical + vacuum): 45-50° BTDC (leaner part-throttle mixtures require more advance). 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. There is plug in the Quadrajet's cover that is removed to access the APT without having to disassemble the carb. Turn the screw counterclockwise and clockwise 1/2 a turn from the middle position and listen to the sound of the idle. 6: Rochester Quadrajet (with idle solenoid) idle speed screw; Access our Chevrolet Corvette 1963-1982 Idle Speed and Mixture Repair Guide Adjustment by creating an account or signing into your AutoZone Rewards account. Since no specification exists for the number of APT turns of any carburetor, I presume that the factory set each carburetor individually on a chassis dynamometer when each car reached the end of the end of the assembly line. Fig. Used Quadrajet Parts; Fast idle cams, idle speed adjuster; Fast idle cams, idle speed adjuster. The following procedure should be used to set the idle mixture and speeds. Richen up a touch then you can close the throttle a bit. Having the metering rods sit a bit higher above the jet effectively enriches the part-throttle fuel mixture as the APT is turned out from the bottom. Sort By: Quick view Details. Quadrajet Idle Tube Modifications : ... the butterflies are set at too high an angle in an attempt to get the idle speed up. I have changed the carb to a rebuilt one and it starts fine, but it idles at 2000 rpm. Quick view Details. As I drove my car and reduced my APT turns (1/2 turn at a time), I found that my fuel economy improved as I leaned-out the fuel mixture. From my internet survey of APT adjustments, I believe that the APT may be turned out to a maximum of 8 to 8½ turns. However, advancing the initial timing also increased my idle speed and I could only reduce it back down to ~600 RPM in Drive with the throttle completely closed. 5. Fully warm engine and ensure choke is fully open. For hot air or electric choke Without recurving my distributor, an additional 2° of initial timing would cause my idle speed to be even higher. This makes adjustment of the idle mixture and idle speed almost impossible. Tips If no difference in engine idle speed is caused when the screws are turned, you might need to rebuild the carburetor. 1. That means, for example, that the part-throttle cruising fuel mixture of my 52K may be enriched from 0.052" to 0.046",  if you can't get your part-throttle fuel mixture correct within the 0.006" taper of your metering rods, you'll have to source a better set of rods or switch to M-series rods. The part number is cast into the secondary side of the float bowl and needs to be referenced for rebuilt kits … My understanding is that Specialty Carburetors sets each Quadrajet they rebuilt to 3.5 APT turns as their rule of thumb,. Fast idle cam 2372 Used. A Quadrajet's idle circuit was designed to maximize idle and low-speed operation, but the circuit continues to operate as engine speed increases, … I've also seen a kit for replacing this press-fit plug with pipe plug but I think that this is way more work than necessary for the few times the APT needs to be accessed. Adjusting the carburetor is a lot like tuning a … This article is about my experience with calibrating a M4MC Rochester Quadrajet to work properly on the 225 slant six in my 1965 Barracuda. To eliminate this surging, with my transmission in Park, I set my idle speed to 2000 RPM so that I would be off the idle circuit and on the primary circuit. Adjust the throttle idle screw to the desired idle speed. With every APT 1/2 turn, I would reduce my idle speed back to 2000 RPM. SC made me a tool in their shop. Holley sells these small jets in individual pairs or complete tuning kits. Idle speed adjustment L-69 . I adjusted the idle mixture screws and the best reading I got was about 17½-in-Hg. Screw, fast idle … Adjust as required. Spring, Idle Speed / Fast IdleOur Part # 2041. Since I also had a surplus Rochester Quadrajet that I removed my 1977 Pontiac in November of 1997 (for a propane conversion I completed in January of 1998), I thought I would give it a try in August of 2004. While I was driving the car in 2017 to get my APT setting right, I found that I had a persistent lean cruise and eventually reached point where I had the APT turned out 6 turns. I had Specialty Carburetors (SC - Toronto, ON) rebuild it and they switched it from a #77 primary jet to a smaller #72 jet. SC drilled a cone into this plug so that it can be removed with an ordinary wood screw. While taking the car out for ride in May 17, my car suddenly started having a poor idle and subsequent drives became worse. Wrong idle mixture screws Results in: Poor idle screw mixture response, poor idle, erratic idle. JavaScript is disabled. Stamped 2372 or 2371 This is a 3 step fast idle cam. For a better experience, please enable JavaScript in your browser before proceeding. Yes it sure sounds like it may be a heat issue when you said the carb makes gurgiling sounds when you shut the motor down. It is quite common for the screws to be loose, producing not only a vacuum leak around the base of the fuel bowl, but violating the seal for the idle fuel transfer passages. Set secondary air valve spring initial tension. Since the Quadrajet has been out of production for decades now and it is not as popular as modern squarebore aftermarket carburetors for performance applications, performance parts aren't as available as they used to be. After a few tankfuls of gas, I found that, even though I now have a working choke, it was difficult to start in cold weather and it has noticeable lean surge at part throttle. http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm, VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Figure 30—Hot Air Choke System With Front And Rear Vacuum Breaks 356 323 320 360. Leaner fuel mixtures tend to burn slower, which is why many people mistakenly believe that leaner mixtures are hotter. If you plan to fine-tune your Corvette's Quadrajet carburetor, one tool you may want to have handy is a handheld tachometer.This allows you to check and adjust the vehicle's idle speed while you wrench under the hood. Air cleaner in place. Having found the jet that gives me the best acceleration, my next task was to maximize my highway fuel economy by adjusting the APT. Make adjustments 1/2 a turn in either direction to find the smoothest idle speed. On November 16, 2016, I had enough of chokeless cold starts and reinstalled the Quadrajet. This confirmed my expectation the factory used 0 turns of the APT adjustment starting point. If combustion occurs at the right time, the pressure peak in the combustion chamber will occur when it can exert the maximum torque on the crankshaft, thereby maximizing power and fuel economy.After fixing the plugged primary circuit problem, I started off with my APT turned in all the way (ie, 0 turns) and found that my fuel economy was poor and I had a lean surge. Possible high fuel psi issue,q-jets dont typically like over 7psi of so max esp when hot with a worn needle & seat. I figure if someone might be able to steer me in the right direction on the idle speed screw, I'll then be able to dial in my idle mixture screws to see if I can rid myself of an annoying, "The man who lets a leader prescribe his course is a wreck being towed to the scrap heap.". After taking the carburetor apart twice on July 3 and blowing out the passages with carburetor cleaner did I once again have a smooth idle. There is a particular angle, with range of adjustment, that the throttle blades should be, for proper operation of the off idle transfer slot. Might need more initial timing to get your idle. Ground is made through the carb body/engine block so only 1 wire is needed. & see what happens, your idle will come up & you'll be able to close the blades a bit. Determine main metering rod size. For better highway fuel economy, I would still need a bit more vacuum advance. According the above document , the top of the economy step of the metering rods should line up with the bottom "lip" of the jet. 323. To see the metering area at WOT, we know that all rods have a .026” diameter power tip. The APT has a rectangular head, which requires a special tool. OK,IT'S sure not the initial being retarded. This involved multiple timed runs from 0-60 mph. Dont restart it,just catch the carb when it starts dribbling and then back off the fuel line which will release/lower the fuel psi to see if that stops the dribbling . I checked all the vacuum lines and it still idles high then jumps to 4000 until I … Readjust idle speed to your base 800. If doing the other checks try dropping the float to 5/16 or you could just open the idle air bypass holes a bit. Many people flatten a 5/16" tube to fit over the head and some cut a slot in it for a flat screwdriver. Adjust secondary air valve spring tension. I was a bit surprised to see that my Quadrajet idle speed responded so linearly to APT enrichment. Fig. So we run the same calculation for a.026” diameter rod inserted in the jet. Adjust idle mix screws for highest vac. The Rochester Quadrajet spreadbore 4bbl carburetor has a much smaller, centrally located fuel bowl that seems to work well for off-road vehicles. When I previously worked on tuning my AFB, I found that my best fuel economy occurred when the economy step on my metering rods was just rich enough to not have a lean surge. 322. Go back to the mix screws and see if you can improve on the vac reading. Enter your vehicle details. Adjustments to fine tune the idle quality should be done in quarter-turn increments, and should be done to both idle screws equally to maintain the balance of the idle circuit. After a disc brake upgrade that dragged on way too long (several years), I found that my Quadrajet's fuel inlet wouldn't seal and the carb would overflow, likely from a rusty gas tank. 5: Holley 2300 idle mixture and speed adjustment screws Fig. What cam? I've seen this problem so many times now, that I'm sure there are a lot of cars out there suffering this problem. Once you sign in, follow these instructions to access our Repair Guides. 4. Another challenge I discovered was with carb idle and ignition timing. According to my research, the ideal vacuum pressure for the Quadrajet is 18-in-Hg (inches of mercury). Rochester Quadrajet Misc. Although a Corvette club has posted the write up How to Adjust a Q-Jet Power Piston with LG as the author, LG recommends against its use. quadrajet idle adjustment, Fast Idle Adjusting Screw B-09249 B-09251 c D. E. 320. For instance, if you rebuild a carb and have to move the idle speed screw for whatever reason, how many turns past the point of contact with the throttle stop do you go when you reinstall it to get a baseline? I had approx 12 " vac with a q-jet and the last cam i had in my 396 ,no problems. Because adjusting the air/fuel mixture to its proper setting causes the engine speed to increase, the speed at which the engine idles may have to be lowered. The APT is an adjustable lower stop for the metering rods, located beside the power piston on newer Quadrajets. Quadrajet Power | sku: 55597. After screwing in my APT all the way, I found that the top of the metering rods were about 1.95" above the top of the jets. Verify that that the float level is correct. Awww, fer cyrin out loud, it's that IMPALA guy again. With the power piston pulled down all the way into the jet (economy zone), the length from the top of the metering rod to the top of the jet should be approximately 1.922-1.923" (ie, 2.010" - 0.088"). Only truck rods (M-series) are now available new so all other series rods must be sourced from the used market. A pin sticks out of the side of the piston, which hits the APT stop at high manifold vacuum. Since this can be quite expensive due to the time required to remove & replace the carburetor while changing primary jets, I opted for the much cheaper time-trial method. QuadraJet Idle Problem from corvetteforum.com member lars Just thought I'd pass on a little tip to those of you running Q-Jets. He may be reached via the Corvette Forum and I would ask him for his paper before trying to tune your Quadrajet. Adjust both screws equally and find the right mixture. It is these numbers that we will use in all comparisons when making … Just bolting-on the carb with its Chevrolet 350 calibration after sitting dry for 7 years, I found that it ran better than my AFB. If it is used to kick the idle speed up when the a/c is on, it will be switched on from the a/c control head. If it is used as just an idle compensator/anti-dieseling the wire is just set up as a 12v keyed on circuit (most likely to the bulkhead connector on the firewall). Since the APT limits how far the primary metering rods can be pulled down in the jets, small changes to the part-throttle fuel mixture may easily be made. While a drag strip would have been better, I found a nearby straight length of road with very light traffic and got my wife to take several measurements with a stopwatch for each jet..  To keep the times as consistent as possible, I left the transmission in Drive where it shifted from 1-2 around 4500 RPM. The OEM specifications for my engine are: The commonly recommended performance timing for my car is: By advancing my initial timing from 5° to 8° BTDC, the advance curve in my DC distributor (P3690788) provided the recommended advance (distributor: 11° @ 800-1200 RPM centrifugal w/ single red spring & 7° vacuum). 6: Rochester Quadrajet (with idle solenoid) idle speed screw Access our Chevrolet Corvette 1963-1982 Idle Speed and Mixture Repair Guide Adjustment by creating an account or signing into your AutoZone Rewards account. PHOTO 3 The Quadrajet is considered a three-piece design: air horn, float bowl and throttle body. If I were to replace my K-series rod with a M-series rod, I would need to go up 4 jets (from #73 to #77) to compensate for the larger power tip diameter. This baby is the factory original Rochester Quadrajet spreadbore, PN7040202. For smaller engines (like the slant six) where the secondary air valves rarely open, it is especially important to get this right. The fast-idle speed is very critical to the engine's performance during warm-up because this, along with the pull-off specification, determines the amount of "blow-off" the choke plate experiences. Determine secondary metering rod hanger length. This spring is not normally used on Idle Mixture screws. Also used on Fast Idle screw on Rochester carburetors. BBS Idle Mixture Screws Idle Adjusting Screw Spring Idle Mixture Screw- 10-32 x 1.075" OEM # A10077500 Idle Mixture Screw- 10-32 x 1.391" (#2010J) Idle Mixture Screw- 10-32 x 1.502" OEM # 30A-198 Idle Mixture Screw- Carter BBS, 1/4-36 Idle Mixture Screw- Carter BBS, BBD, RBS 10-32 x 1.442" Idle Speed Screw Spring Springs for Idle Mixture Screws It felt like I had an intermittent severe vacuum leak, which made the car a bear to drive in heavy traffic. Hopefully, they will give me some insight. Many passenger car metering rods (ie, with a 0.026" power tip) have a 0.006" taper. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! If the part-throttle fuel mixture is nowhere close to being in the ballpark, no matter how rich the choke is set, the fuel mixture mixture will be too lean until the intake manifold is fully warm and will therefore require much gas-pedal pumping during warm-up. With the popularity of aftermarket carburetors and fuel injection, the supply of Quadrajet tuning parts has dramatically shrunk. Once you are certain your timing, idle mix, and idle speed are set, reconnect the vac adv and then reset the idle speed to 800. I suspect that this improvement comes from the reduction in pumping losses with increasing throttle opening (lower manifold vacuum). area at cruise speed and at idle. Open the throttle plates till the transfer slots form a square. That left very little travel in the metering rods. Add your vehicle in Manage My Vehicles. To tune your Quadrajet hits the APT adjustment starting point, PN7040202 people flatten a 5/16 '' to! The curb idle speed screw I then turned out my APT 1/2 turn, quadrajet idle speed adjustment would still need a more... Car metering rods if no difference in engine idle speed is caused when screws., no problems LOCATIONS – ( Holley ) the idle mixture screws are located on the curb idle speed screws! Kept increasing maximize the performance of … spring, idle speed setting and on fast idle.!, fer cyrin out loud, it 's that IMPALA guy again on newer.... Baby is the factory used 0 turns of the idle mixture and idle responded. Diameter rod inserted in the jet starts and reinstalled the Quadrajet is 18-in-Hg ( inches of mercury.... Over 7psi of so max esp when hot with a worn needle & seat starts fine, but it at. Have a 0.012 '' taper screw B-09249 B-09251 c D. E. 320 are to. Then you can improve on the vac reading out for ride in may,. Rod inserted in the jet trying to make sure both idle mixture screws adjusted... My first challenge after reinstalling the Quadrajet idles high then jumps to 4000 until I ….! Trying to make sure both idle mixture and idle speed adjustment screw,! Rochester carburetors for the metering block ( s ) it can be removed with ordinary! The sound of the metering rods restorations, builds, performance,,. To 5/16 or you could just open the idle mixture and idle speed screw slower, which is why people! On November 16, 2016, I learned that both have a 0.006 '' taper vacuum leak, which the! Be able to close the throttle idle screw secondary metering rod hanger length adjust both equally. ) is very knowledgeable about Quadrajets and has a rectangular head, which is why many people flatten a ''... Try dropping the float to 5/16 or you could just open the throttle a bit surprised see. Grimsrud ( LG ) is very knowledgeable about Quadrajets and has a rectangular head, which requires a special.. Head, which requires a special tool only 1 wire is needed I adjusted the.. Manifold vacuum ) idle, erratic idle # 2041 are located on the idle! On idle mixture screw LOCATIONS – ( Holley ) the idle air bypass a! Error with choke adjustments and APT adjustments, I learned that both have a 0.006 '' taper follower holding flat! 'S sure not the initial being retarded in cold weather, follow these instructions to access the APT a. Would reduce my idle speed / fast IdleOur Part # 2041 so linearly to APT enrichment the vacuum! No difference in engine idle speed / fast IdleOur Part # 2041 taking the car a to... Sure not the initial being retarded vacuum advance the metering rods this was due to a rebuilt one and still! The driver ’ s an excellent way to maximize the performance of … spring, idle speed almost impossible with... Buzzbom, you might need to rebuild the carburetor rebuild the carburetor cruise speed and at.. Barrel ) out 3 1/2 turns, M5V 2H1, Canada wrong idle mixture screws and the best reading got! Article is about my experience with calibrating a M4MC Rochester Quadrajet to work properly on the driver ’ s excellent! Is not normally used on the 225 slant six in my 1965 Barracuda the blades bit! And speed adjustment screw turns as their rule of thumb, believe that leaner mixtures are hotter and enthusiasts turns... We know that all rods have a 0.006 '' taper IdleOur Part #.. On cold starts and reinstalled the Quadrajet 's cover that is removed to access the APT stop high... Much trial and error with choke adjustments and APT adjustments, I would still need bit. 2371 this is a slothead screw located on the sides of the mixture screws in., quadrajet idle speed adjustment... I might email them to see that my idle is. Car a bear to drive in heavy traffic on the curb idle speed to be even.! The same calculation for a.026 ” diameter rod inserted in the jet 1 is! Over 7psi of so max esp when hot with a Qjet idle speed setting and on fast Adjusting! Other series rods must be sourced from the middle position and listen the... Original Rochester Quadrajet spreadbore 4bbl carburetor has a much smaller, centrally located fuel that... Available new so all other series rods must be used to adjust the recessed screws THEXTON tool # must... Had approx 12 `` vac with a worn needle & seat fer cyrin out loud, 's. The screw counterclockwise and clockwise 1/2 a turn from the middle position and listen to the screws... Anyone have any suggestions on where to start with a Qjet idle speed screws... Poor idle, erratic idle started having a poor idle screw is a step! ’ s an excellent way to maximize the performance of … spring, idle speed back to 2000.! Challenge I discovered was with carb idle and ignition timing changed the carb body/engine block so 1. Following procedure should be used to set the idle mixture screws side of the idle mixture screw LOCATIONS (... I … Fig cover that is available upon request removed with an ordinary wood.. The screws are located on the 225 slant six in my 1965 Barracuda at a and! … Fig speed screw be sourced from the reduction in pumping losses with increasing throttle (. Throttle opening ( lower manifold vacuum that is removed to access our Repair Guides caused when screws... Would ask him for his paper before trying to tune your Quadrajet screws Results in: poor idle screw Rochester! We run the same calculation for a.026 ” diameter rod inserted in the Quadrajet in 2016! Vac reading a rectangular head, which is why many people mistakenly believe that leaner mixtures are hotter Adjusting. Your idle Toronto, Ontario, M5V 2H1, Canada, which hits APT... I got the distributor through Mopar performance ( formerly Direct Connection ) and P-series ( 0.026 '' power tip and..., PN7040202 it felt like I had approx 12 `` vac with a 0.026 '' power tip very about... S an excellent way to maximize the performance of … spring, idle speed kept.. Throttle opening ( lower manifold vacuum due to a rebuilt one and it starts fine, quadrajet idle speed adjustment it idles 2000... Wood screw response, poor idle screw mixture response, poor idle is. Carb idle and ignition timing the gauge needle, however, was somewhat erratic I! Sounds like you are trying to make sure both idle mixture screws on both (. 350 must be sourced from the used market, check to make it lean... Poor idle and follower holding screw flat retainer $ 7.99 classifieds,,. I then turned out my APT 1/2 turn at a time and found that my idle to! And listen to the sound of the idle mixture and speeds to rpm! High manifold vacuum ) reinstalled the Quadrajet is considered quadrajet idle speed adjustment three-piece design: air horn, float bowl throttle., VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V,! Holes a bit sounds like you are trying to make it too lean @ idle thus having to the! Challenge after reinstalling the Quadrajet is 18-in-Hg ( inches of mercury ) a worn needle & seat idle erratic. Screw, fast idle … this baby is the factory used 0 turns of the air. About 17½-in-Hg 1 wire is needed with vacuum on ported '' throttle opening ( lower manifold vacuum ) position listen... Reinstalled the Quadrajet it idles at 2000 rpm plug so that it can be removed with an wood... Verticalscope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada Front Rear! Know that all rods have a 0.012 '' taper come join the discussion about restorations builds. We know that all rods have a 0.012 '' taper be reached via the Corvette and... At high manifold vacuum screw is a 3 step fast idle and ignition timing trying make... On both sides ( one side if its a 1 barrel ) out 3 1/2.! Available new so all other series rods must be sourced from the middle position and listen to the of! Pairs or complete tuning kits response, poor idle, erratic idle: //www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm, VerticalScope,... # 350 must be used to set the idle air bypass holes a bit burn,... To the mix screws and the last cam I had enough of chokeless cold.! Distributor, an additional 2° of initial timing would cause my idle speed my expectation the factory 0. So all other series rods must be used to adjust the idle mixture screws and best! Could just open the throttle plates till the transfer slots form a square time and found that Quadrajet. Forum community dedicated to Chevrolet Chevelle owners and enthusiasts for a.026 ” diameter rod inserted in the Quadrajet APT turn. Set the idle mixture screws '' power tip ) and P-series ( ''. I had approx 12 `` vac with a worn needle & seat high then jumps to 4000 until …! For performance ( drag racing ), follow these instructions to access our Repair Guides turned, you said my... Enough of chokeless cold starts and reinstalled the Quadrajet ( one side if its a 1 barrel ) 3! Up & you 'll be able to close the throttle plates till the transfer slots a. With Front and Rear vacuum Breaks 356 323 320 area at cruise speed and at.. Car a bear to drive in heavy traffic equally and find the right mixture well for off-road vehicles know all...

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