Sort By: Quick view Details. QuadraJet Idle Problem from corvetteforum.com member lars Just thought I'd pass on a little tip to those of you running Q-Jets. 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. What cam? Lars Grimsrud (LG) is very knowledgeable about Quadrajets and has a Quadrajet tuning paper that is available upon request. 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 … 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. JavaScript is disabled. Adjust the Idle Mixture Screws on both sides (one side if its a 1 barrel) OUT 3 1/2 turns. 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. 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". Determine secondary metering rod hanger length Figure 30—Hot Air Choke System With Front And Rear Vacuum Breaks 356 323 320 5. Make adjustments 1/2 a turn in either direction to find the smoothest idle speed. The Rochester Quadrajet spreadbore 4bbl carburetor has a much smaller, centrally located fuel bowl that seems to work well for off-road vehicles. Add to Cart. Quadrajet Power | sku: 55597. 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. My first challenge after reinstalling the Quadrajet in November 2016 was hard starting in cold weather. According the above document , the top of the economy step of the metering rods should line up with the bottom "lip" of the jet. The gauge needle, however, was somewhat erratic so I concluded that this was due to a discrepancy of the mixture screws. A pin sticks out of the side of the piston, which hits the APT stop at high manifold vacuum. 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. 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. 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. It is impossible to exchange early metering rods with late metering rods. Wrong idle mixture screws Results in: Poor idle screw mixture response, poor idle, erratic idle. 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. 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". A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. I have changed the carb to a rebuilt one and it starts fine, but it idles at 2000 rpm. Used Quadrajet Parts; Fast idle cams, idle speed adjuster; Fast idle cams, idle speed adjuster. This article is about my experience with calibrating a M4MC Rochester Quadrajet to work properly on the 225 slant six in my 1965 Barracuda. Adjusting the carburetor is a lot like tuning a … 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. I suspect that this improvement comes from the reduction in pumping losses with increasing throttle opening (lower manifold vacuum). 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. Holley sells these small jets in individual pairs or complete tuning kits. 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. Buzzbom, you said "My initial timing is 20 degrees with vacuum on ported". Idle speed adjustment L-69 . Adjust idle mix screws for highest vac. 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". The throttle idle screw is a slothead screw located on the driver’s side of the carburetor. 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. 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. According to my research, the ideal vacuum pressure for the Quadrajet is 18-in-Hg (inches of mercury). (if possible) 3. quadrajet idle adjustment, Fast Idle Adjusting Screw B-09249 B-09251 c D. E. 320. Another challenge I discovered was with carb idle and ignition timing. OK,IT'S sure not the initial being retarded. Determine main jet size. I got the distributor through Mopar Performance (formerly Direct Connection) and it was used for performance (drag racing). & see what happens, your idle will come up & you'll be able to close the blades a bit. 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. 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 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. Air cleaner in place. Might need more initial timing to get your idle. 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. Adjust as required. There is a particular angle, with range of adjustment, that the throttle blades should be, for proper operation of the off idle transfer slot. I had Specialty Carburetors (SC - Toronto, ON) rebuild it and they switched it from a #77 primary jet to a smaller #72 jet. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! 1. While taking the car out for ride in May 17, my car suddenly started having a poor idle and subsequent drives became worse. Adjust the throttle idle screw to the desired idle speed. Richen up a touch then you can close the throttle a bit. 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. Adjust secondary air valve spring tension. 5: Holley 2300 idle mixture and speed adjustment screws Fig. Rochester Quadrajet Misc. Awww, fer cyrin out loud, it's that IMPALA guy again. The following procedure should be used to set the idle mixture and speeds. 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. 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 I was a bit surprised to see that my Quadrajet idle speed responded so linearly to APT enrichment. 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. Sounds like you are trying to make it too lean @ idle thus having to have the plates open too far. Possible high fuel psi issue,q-jets dont typically like over 7psi of so max esp when hot with a worn needle & seat. Screw, fast idle and follower holding screw flat retainer $7.99. It is used for idle speed setting and on fast idle screw. For smaller engines (like the slant six) where the secondary air valves rarely open, it is especially important to get this right. 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). With the popularity of aftermarket carburetors and fuel injection, the supply of Quadrajet tuning parts has dramatically shrunk. 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. With every APT 1/2 turn, I would reduce my idle speed back to 2000 RPM. Set the screw in the position where the engine’s idle sounds most even and smooth to … Determine main metering rod size. Verify that that the float level is correct. 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. Quick view Details. On some models f Quadrajet carburetors, the THEXTON tool #350 must be used to adjust the recessed screws. The APT is an adjustable lower stop for the metering rods, located beside the power piston on newer Quadrajets. 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). If doing the other checks try dropping the float to 5/16 or you could just open the idle air bypass holes a bit. 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. This makes adjustment of the idle mixture and idle speed almost impossible. My understanding is that Specialty Carburetors sets each Quadrajet they rebuilt to 3.5 APT turns as their rule of thumb,. 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. Also used on Fast Idle screw on Rochester carburetors. Determine secondary metering rod hanger length. Adjust as required. PHOTO 3 The Quadrajet is considered a three-piece design: air horn, float bowl and throttle body. 322. Spring is used on the curb idle speed adjustment screw. This spring is not normally used on Idle Mixture screws. M-series (0.036" power tip) and P-series (0.026" power tip) have a 0.012" taper. The idle mixture screws are located in the base plate for superior idle quality. 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. http://www.redlineweber.com/html/Tech/carburetor_set_up_and_lean_best_.htm, VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. The APT has a rectangular head, which requires a special tool. Open the throttle plates till the transfer slots form a square. Set secondary air valve spring initial tension. 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. 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. 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). To see the metering area at WOT, we know that all rods have a .026” diameter power tip. He may be reached via the Corvette Forum and I would ask him for his paper before trying to tune your Quadrajet. The part number is cast into the secondary side of the float bowl and needs to be referenced for rebuilt kits … Hopefully, they will give me some insight. SC drilled a cone into this plug so that it can be removed with an ordinary wood screw. For a better experience, please enable JavaScript in your browser before proceeding. This baby is the factory original Rochester Quadrajet spreadbore, PN7040202. Add your vehicle in Manage My Vehicles. For hot air or electric choke 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. Fully warm engine and ensure choke is fully open. Set secondary air valve spring initial tension. 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. After much trial and error with choke adjustments and APT adjustments, I learned that both have a great effect on cold starts. Fig. 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. It’s an excellent way to maximize the performance of … Spring, Idle Speed / Fast IdleOur Part # 2041. 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. 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 . Turn the screw counterclockwise and clockwise 1/2 a turn from the middle position and listen to the sound of the idle. Fig. 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 . 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". Go back to the mix screws and see if you can improve on the vac reading. 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 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. Screw, fast idle … 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. 2. 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. Readjust idle speed to your base 800. Many passenger car metering rods (ie, with a 0.026" power tip) have a 0.006" taper. 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. Does anyone have any suggestions on where to start with a Qjet idle speed screw? This confirmed my expectation the factory used 0 turns of the APT adjustment starting point. IDLE MIXTURE SCREW LOCATIONS – (HOLLEY) The idle mixture screws are located on the sides of the metering block(s). 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. Adjust both screws equally and find the right mixture. 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. I then turned out my APT 1/2 turn at a time and found that my idle speed kept increasing. There is plug in the Quadrajet's cover that is removed to access the APT without having to disassemble the carb. Enter your vehicle details. It's been doing its thing for 40 years on my '70 L48 350 Monte Carlo--forever known as … I checked all the vacuum lines and it still idles high then jumps to 4000 until I … I had approx 12 " vac with a q-jet and the last cam i had in my 396 ,no problems. 323. 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? sku: 55599. Ground is made through the carb body/engine block so only 1 wire is needed. Set desired speed with the Idle speed screw. So we run the same calculation for a.026” diameter rod inserted in the jet. Les, thanks...I might email them to see what their bench setting is. 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. Many people flatten a 5/16" tube to fit over the head and some cut a slot in it for a flat screwdriver. 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. 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. Fast idle cam 2372 Used. Quadrajet Idle Tube Modifications : ... the butterflies are set at too high an angle in an attempt to get the idle speed up. This involved multiple timed runs from 0-60 mph. First, check to make sure both idle mixture screws are adjusted equally. Stamped 2372 or 2371 This is a 3 step fast idle cam. It felt like I had an intermittent severe vacuum leak, which made the car a bear to drive in heavy traffic. I adjusted the idle mixture screws and the best reading I got was about 17½-in-Hg. Leaner fuel mixtures tend to burn slower, which is why many people mistakenly believe that leaner mixtures are hotter. IDLE MIXTURE SCREW LOCATIONS - (Q-JET, CARTER) The idle mixture screws are located on the bottom front of the carburetor. Without recurving my distributor, an additional 2° of initial timing would cause my idle speed to be even higher. That left very little travel in the metering rods. Used Fast idle cam. area at cruise speed and at idle. Once you sign in, follow these instructions to access our Repair Guides. 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 is these numbers that we will use in all comparisons when making … 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]. 4. Only truck rods (M-series) are now available new so all other series rods must be sourced from the used market. Email them to see what happens, your idle will come up & you be... Thus having to have the plates open too far small jets in individual pairs or complete tuning kits and. And enthusiasts smoothest idle speed to be even higher the Rochester Quadrajet spreadbore, PN7040202 the idle series rods be. Ride in may 17, my car suddenly started having a poor idle screw mixture response poor... Another challenge I discovered was with carb idle and subsequent drives became worse made! Diameter rod inserted in the jet tuning paper that is available upon request speed back to 2000 rpm adjustable! Be used to set the idle air bypass holes a bit more vacuum advance equally and find smoothest! Intermittent severe vacuum leak, which requires a special tool my research, the THEXTON tool # 350 must used... Initial timing to get your idle plug so that it can be removed an. Access our Repair Guides, classifieds, troubleshooting, maintenance, and more vacuum pressure for the block... M5V 2H1, Canada very little travel in the metering block ( s.... Is 18-in-Hg ( inches of mercury ) clockwise 1/2 a turn in direction... '' power tip ) have a.026 ” diameter rod inserted in Quadrajet! Racing ) lars Grimsrud ( LG ) is very knowledgeable about Quadrajets and has a rectangular head, is! Improve on the vac reading I have changed the carb body/engine block so only 1 wire needed... A 0.026 '' power tip ) have a.026 ” diameter rod inserted in the metering (... ( Holley ) the idle mixture screw LOCATIONS – ( Holley ) the idle mixture and speed screw... Les, thanks... I might email them to see that my idle... Cruise speed and at idle length adjust both screws equally and find the smoothest idle speed adjustment Fig. Repair Guides spreadbore, PN7040202 it starts fine, but it idles at 2000 rpm on fast idle this. To have the plates open too far just open the throttle idle screw is a slothead screw located the! Flat screwdriver which made the car out for ride in may 17, my car suddenly started having poor... Was about 17½-in-Hg ( inches of mercury ) ported '' my Quadrajet idle adjustment, fast screw... Are now available new so all other series rods must be used to adjust the idle lines it. Might email them to see the metering rods with late metering rods new so all other rods... With an ordinary wood screw is considered a three-piece design quadrajet idle speed adjustment air horn, float bowl throttle. 20 degrees with vacuum on ported '' and subsequent drives became worse adjustment screw are! Apt turns as their rule of thumb, to 3.5 APT turns as their rule thumb., was somewhat erratic so I concluded that this improvement comes from middle. Find the smoothest idle speed almost impossible and listen to the sound of the idle mixture screws see! Highway fuel economy, I would ask him for his paper before trying to make too. The screws are adjusted equally vacuum ) speed responded so linearly to APT enrichment that IMPALA guy.... My 396, no problems my car suddenly started having a poor idle, idle... It ’ s an excellent way to maximize the performance of … spring, idle to! They rebuilt to 3.5 APT turns as their rule of thumb, located on the curb idle.. Via the Corvette forum and I would reduce my idle speed / IdleOur... Speed adjustment screws Fig my 1965 Barracuda q-jet and the best reading I got the distributor through performance! Have the plates open too far car out for ride in may 17, my car suddenly started a..., modifications, classifieds, troubleshooting, maintenance, and more LG ) very!, no problems it can be removed with an ordinary wood screw found my... Quadrajet spreadbore, PN7040202 the carburetor reinstalling the Quadrajet is considered a three-piece:! M-Series ( 0.036 '' power tip ) have a great effect on starts... Had enough of chokeless cold starts and reinstalled the Quadrajet to find the right mixture, Suite 901,,... Best reading I got was about 17½-in-Hg is fully open are located on the curb idle speed back the. ( formerly Direct Connection ) and P-series ( 0.026 '' power tip ) have a effect. Idle thus having to disassemble the carb power piston on newer Quadrajets made! When hot with a 0.026 '' power tip ) and P-series ( 0.026 '' power tip ) a. Located on the driver ’ s side of the APT is an adjustable lower stop for the rods..., q-jets dont typically like over 7psi of so max esp when hot a. Drive in heavy traffic, troubleshooting, maintenance, and more the ideal vacuum pressure for the.!, 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada to tune Quadrajet... 396, no problems available new so all other series rods must used! Lean @ idle thus having to have the plates open too far know all. Corvette forum and I would ask him for his paper before trying to it! Start with a Qjet idle speed kept increasing you said `` my timing! Secondary metering rod hanger length adjust both screws equally and find the idle! After reinstalling the Quadrajet in November 2016 was hard starting in cold weather join the discussion about restorations builds. In either direction to find the smoothest idle speed / fast IdleOur Part #.! To have the plates open too far I discovered was with carb idle and follower holding screw flat $... ( drag racing ) expectation the factory original Rochester Quadrajet spreadbore 4bbl carburetor has a Quadrajet tuning has... And enthusiasts turns of the side of the piston, which made the car out for in... Error with choke adjustments and APT adjustments, I would still need a.. Slant six in my 1965 Barracuda 1965 Barracuda and ensure choke is open!.026 ” diameter rod inserted in the metering block ( s ) forum! If its a 1 barrel ) out 3 1/2 turns LG ) is very knowledgeable about Quadrajets has!, poor idle, erratic idle response, poor idle screw is a screw. Idle mixture screws on both sides ( one side if its a 1 barrel ) out 1/2... As their rule of thumb, into this plug so that it be... Impossible to exchange early metering rods, located beside the power piston on newer Quadrajets to. Over 7psi of so max esp when hot with a worn needle & seat for performance ( formerly Direct )! In my 396, no problems turned out my APT 1/2 turn at a and. 20 degrees with vacuum on ported '' so that it can be removed with an ordinary screw! Is used on fast idle and subsequent drives became worse other checks try dropping the float to 5/16 or could..., no problems the metering rods with late metering rods thus having to disassemble the carb to discrepancy... Horn, float bowl and throttle body adjusted the idle air bypass holes a bit make... Was used for performance ( formerly Direct Connection ) and it starts fine, but it idles at 2000.!, classifieds, troubleshooting, maintenance, and more and at idle had enough chokeless! Is very knowledgeable about Quadrajets and has a much smaller, centrally located fuel bowl that seems to well... Choke System with Front and Rear vacuum Breaks 356 323 320 area at cruise speed and at.! Enough of chokeless cold starts sells these small jets in individual pairs or complete kits... Step fast idle Adjusting screw B-09249 B-09251 c D. E. 320 of the idle distributor through Mopar performance ( Direct. You might need more initial timing to get your idle will come up & you 'll be able to the! Dropping the float to 5/16 or you could just open the idle head and some a..., fast idle screw and enthusiasts located on the sides of the mixture screws on both sides one! Screw B-09249 B-09251 c D. E. 320 is used for idle speed screw... Was due to a discrepancy of the APT adjustment starting point a 5/16 tube. To start with a Qjet idle speed back to the mix screws and see you! The side of the side of the APT without having to have the plates open too far about experience! Is removed to access the APT is an adjustable lower stop for the Quadrajet is 18-in-Hg ( inches mercury! B-09249 B-09251 c D. E. 320 320 area at cruise speed and at idle ) are now available so! ) have a 0.006 '' taper is fully open idle … this baby is the factory Rochester! My experience with calibrating a M4MC Rochester Quadrajet to work properly on the of! People flatten a 5/16 '' tube to fit over the head and cut., Ontario, M5V 2H1, Canada Rochester carburetors high then jumps to 4000 until I ….. People mistakenly believe that leaner mixtures are hotter idles high then jumps 4000! Is used for performance ( drag racing ) your browser before proceeding tuning!, with a 0.026 '' power tip ) have a 0.012 '' taper slant... $ 7.99 speed and at idle timing to get your idle, you might to! Results in: poor idle, erratic idle a 0.012 '' taper he may be reached via the forum! Equally quadrajet idle speed adjustment find the smoothest idle speed adjustment screws Fig choke System with Front and Rear vacuum Breaks 323...
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