See more Reply Save Like 2 2old2fast Opening rate of the secondary air valves (flaps) is controlled by two things, spring tension and the choke pull-off (round pod with vacuum line connected). Because the Quadrajet is so versatile, it is easy to find a suitable core for your GM V-8 project. It is when it's time to get it on the Quadrajet struggles to deliver when we don't get fuel delivery and throttle action properly timed. Racks, Fish Finders, Sounders q-jets have had problems w/ worn accel. The Quadrajet fuel bowl is one big continuous reservoir for all four bores. Helm Seats, Shop Privacy Policy. GPS Chartplotter and Fish Finder Combo, Find Login, Boats Details: SBC 350 - Stock high mileage motor Quadrajet - APT screw turned out 1.5 turns from bottom w/ 67 jets. A forum community dedicated to hot rod owners and enthusiasts. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. I have a quadrajet on the 454 in my truck, electric choke etc. JavaScript is disabled. Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. Oars, Wakeboard, Wakesurf & Kind of an enrichment/acceleration feed to get the fuel sucking through the secondary bores. for Sale, Buy A Harware, Marine Nuts, Bolts, & Daytona Beach, FL. Float level may be too low set to specifications. Accessories, PWC Parts & The vacuum operated air valves above the secondaries, when properly adjusted, open at a slower clip to compensate for the large mechanical secondary throttle plates, which open quickly causing that legendary bog/lag Quadrajets are known for. http://www.73-87.com/7387garage/drivetrain/myqjet.htm. Maybe the choke is open too far? "Detroit hasn't felt any real pride since George Bush went to Japan and vomited on their auto executives, I tell you whut". Details: SBC 350 - Stock high mileage motor Quadrajet - APT screw turned out 1.5 turns from bottom w/ 67 jets. Non computer controlled (1986). Secondary fuel metering can therefore be altered by changing these rods, easily performed without having to disassemble the carb. Fishing Lures, Fishing Rod Holders & Systems, Marine Plumbing Float level may be too low set to specifications. If it is set to open too soon, the excess fuel will bog the engine because it can't handle it until the rpms rise. Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. Look at it, it lifts the metering rods back there at the secondarys and hence fuel floes through the jets.That is how the secondary cicuit is metered. Fuel filters are dirty, or plugged replace any in-line filter and the filter at the carburetor fuel inlet. I tried to use the search before I asked this question because I know this subject has been gone over and over but I can't find anything exactly like my issue. So i couldn't hold the bottom fitting while i twisted the top to get the pick up out. This thing runs great, starts every time and idles nice. The higher the letter in the alphabet, the earlier it raises the metering rods during air valve opening. Rails, Marine Tools & Tool Different pull-offs have different release rates. Sounds like a possible float issue to me. Everything everyone else has said is good to check, but I have one more possibility: I had a '73 Cutlass that was doing pretty much the same thing, and it was the spark plug wires. For a better experience, please enable JavaScript in your browser before proceeding. To this day, many record-holding Super Stock cars run well into the nine second zone with Q-Jets atop their manifolds. The stock air valve spring setting is usually 1/2 to 3/4 turn from loose. But then again, that side doesn't half fuel sitting it in most of the time. It's a QuadraJet. Most modern Deals, Pumps & Plumbing During recent runs, engine bogs at 2500 rpm (normal WOT is about 4000), starts to choke a little. A Quadrajet rebuild is actually quite simple. Another possibility, and it is real. Good for the interstate cruise. The boat is going out early Saturday morning, so if it was just the valve and all works, then sweet. 1,364. The E4M/CCC solenoid actuated system replaced the vacuum controlled power piston used in conventional 4M Quadrajet carburetors. Everything everyone else has said is good to check, but I have one more possibility: I had a '73 Cutlass that was doing pretty much the same thing, and it was the spark plug wires. Jan 19, 2011. Most modern If I have it in 3rd gear, 40 mph and hold it WOT it will pull strong to approx 3,000-3,500 before it bogs. For a better experience, please enable JavaScript in your browser before proceeding. The car ran, but would bog on acceleration and backfire through the carb too. Make sure the timing is not delayed due to a slipped timing mark or too much vacuum advance (20-30 degr.). It needs to be loosened, and the air door spring tension adjusted. You guys are always helpful here - and I'm kind of stumped on an issue with the Quadrajet and my engine. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! It's suggested you find a virgin core that has never been rebuilt or even a new old stock unit if you can find it. 1,364. 3. A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Trailer Winches, Shop Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Varnish, Marine Adhesives, Accelerates smoothly and with no problem. Biminis, View Locks, Boat Deck Another possibility, and it is real. Hitches, & It controls the air door, if the air door opens too quickly it will hesitate. Swap meets are another excellent place to find a good core. There isn't much you have to do to the Quadrajet to get it to perform in a box-stock application. Have you had the sender unit out the tank and inspected the sock filter? Hello i have a 1967 el camino 327 small block with a rochester quadrajet carb and a turbo 400 trans. Ford did it via the 4300/4300D/4350 carburetors. Just set it to 675 hot neutral idle and you'll be happy. Check the fuel tank vent and the anti-syphon check valve. Another possibility, and it is real. I started up and checked for leaks everywhere before i left, and i noticed as weird as it sounds, my idle was lower. and it seemed like i was running rich. Make sure the timing is not delayed due to a slipped timing mark or too much vacuum advance (20-30 degr.). Ted's Carburetor Service (TCS) inventories plenty of Quadrajet cores, which is terrific if you're looking for a rebuildable core and a good match. All employ air valve transition into the secondaries. See more Reply Save Like 2 2old2fast Vacuum leaks can pop up elsewhere, too, between carburetor body contact surfaces and vacuum ports. If your car or truck is equipped with a Holley four barrel carburetor and stumbles upon acceleration, more than likely the carburetor needs an adjustment to the accelerator pump assembly. But, I'm sure it wasn't helping the situation. Before we go any further, the "CCC" (Computer Command Control) electronic control Quadrajet, known as the "E4M", cannot be used on a non-CCC vehicle. The first round of Quadrajet improvements came in 1968 with the APT (adjustable part throttle) feature, which enabled more finite tuning and a smoother transition from idle to power circuit. I have a quadrajet on the 454 in my truck, electric choke etc. All rights reserved. Accelerates smoothly and with no problem. Petite primary bores keep fuel consumption to a minimum. PM me for more information. JavaScript is disabled. I don't think your problem is the carburator. The secondary pull-off operates off of vacuum and keeps the secondary air valve closed until a low vacuum condition exists (WOT). Getting the Quadrajet to perform is a matter of getting air valve activation in perfect time with fuel delivery and engine rpm. A forum community dedicated to hot rod owners and enthusiasts. Covers, Boat Wiring & Everything I can tell says that the carb is tuned right - here's the run down on whats happening: and i'll try and be as specific as possible so sorry if this is a bit long. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Meters, Marine Electrical Panels For a better experience, please enable JavaScript in your browser before proceeding. It may not display this or other websites correctly. All performance applications should ensure that the air valve opens to a full 90. The rod connects to the choke unloader which serves as: 1. WebJET Performance offers remanufactured Rochester Quadrajet carburetors and tuning kits. Here is a scenario that may help. One nice thing about the Quadrajet is fuel economy if you keep your foot out of it. Rafts, Paddle 1160 hours on engine. Caulking, Marine Engine Accessories, Pontoon Bimini Because GM's Rochester Carburetor Division produced so many Quadrajets in 25 years there's still a generous inventory of cores out there to choose from. Parts, Sacrificial Anodes & If the choke could be the problem since it's only when it's cold how would I check that? Its main(only) function is to open the jets in the secondary circuit. This is known as electronic mixture control. 04. You must log in or register to reply here. Is that correct? Test the solenoilds, the choke has one on the throttle and secondaries blades. JavaScript is disabled. ACCOUNT, Find & Circuit They are notorious for leaking since they are only press-fit from the factory. Unless I let off the throttle, the engine would die. The pull-off is connected by a linkage rod. Deals, Boat Seats Accessories, Marine Electrical It's a QuadraJet. The Quadrajet four-barrel carburetor was produced by the Rochester Carburetor Division of General Motors from 1965-'90. Two "buttons" on front of carb are probably caps covering your primary idle adj. Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. You can modify the choke unloader to speed up the opening rate to 1 to 1 1/2 seconds. Software, Digital Telescopes, Covers and One mistake performance enthusiasts make is not getting the fuel curve to match the powerband. Edelbrock offers 0.041 (EDE1951) and 0.066 (EDE1954) metering rods for performance tuners. While a traditional, square-bore 4150 or 4500 series Holley 4BBL may offer the absolute maximum performance required for all-out drag or circle track racing, a properly prepared Quadrajet, or Q-Jet, can certainly give them a run for the money. Covers, Boat Cover Grills, Boat Drink Thanks you guys im going to be working on the elky in a while ill check it out. Also check the choke pull off diaphram and vacuum advance can for leaks. Upon disassembly, the air horn and main body, in particular, should be inspected for straightness as they can become damaged from over-tightening the carb to the manifold. Well, my ignition coil went out so when I replaced it I pulled the rotor off and checked the distributor weights and they are working fine. did you pull the manifold? The check valve side wasn't bad. The secondary air valves, located in the air horn, allow a smooth transition into the secondaries via manifold vacuum at wide-open throttle. Research the jetting. Fuel metering has to follow the engine's power curve, which keeps torque and horsepower coming. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. Fuel metering rods pulse rapidly as a means to precisely control the air/fuel mixture. I realized that some of the pieces to connect the choke are gone. Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife. I then pulled off the fuel line from the F/W separator - poured some seafoam into the line and then blew it through the knocked out valve and down the tube. Copyright 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. BUT even if the air valve is completely loose it won't cause a bog till the secondary butterflies are opened at the "tip in" point. The Fora platform includes forum software by XenForo. H-P Books offers a Rochester Carburetor book (#HPPHP014) for those desiring further information. it is a small pin on the passenger side of the carb. Deals, Paint & Maintenance Tubes, Shop I then took out the fuel-filter at the carb, and for all intents and purposes it looked brand new. That's the best all around deal. Zincs, Generator Seats, Offshore Boat New motor with only 350 miles on it so I'm trying to be nice to it. WebEp: 25 in this video I show how to fix a hesitation and/or bogging issue with carburetors by adjusting secondaries. The best approach to a Quadrajet rebuild is to open all passages and make sure they are clear. Fuel metering became electronically controlled in 1980. Small-blocks through 350 ci are happiest with 750 cfm. You must log in or register to reply here. In fact, under normal driving conditions the Quadrajet performs quite well. Holders, Cabin Accessories & Switches, Shore Power & AC You must log in or register to reply here. WebHow to de-bog your Quadrajet part 1 Tyler's Forgotten Car Rescue 34.4K subscribers 169K views 12 years ago Sorry guys, I got the videos a bit out of order. there are other things inside a Q jet that could cause it like bent primary rod hanger, dirt in the wrong place, etc. Pumps, Marine Pump Replacement But, if you try to jump on it, let's say more than 1/2 throttle all at once, the car sounds like it is backfiring or popping in the carb. If you open the secondarys it "may" bog? This is definitely where I would start. I'm having a problem with bogging when the engine is cold. WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. If the secondaries open too fast there is not enough vacuum signal to get the fuel flowing and you get bog. thanks NH! Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. The power Piston is stuck in the q jet. it's all the way out in the pic. This may be a fuel delivery problem. If I have it in 3rd gear, 40 mph and hold it WOT it will pull strong to approx 3,000-3,500 before it bogs. I'm not Mike but I'm pretty up on Quadrajets and have worked with them quite a bit. If it is connected correctly. Ski, Wakeboard Tops, Bimini Top It catches up and kicks butt afterward, but it has a pretty serious hesitation first. By comparison, a "square bore" carburetor has primary and secondary venturis of similar size. It was produced in many forms, including electronic-control from 1980-'90, for a wide variety of GM applications. That check valve being coroded up badly was the main culprit!1 The paper filter -likely was catching the crap from that corosion!! merry christmas RLS. I am no expert on the Q-jet, so I'd like some thoughts on adjustment. The idle is set at 900rpm without vaccume advance plugged in. Biminis, RV & Trailer When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). Boat, Sell A Quadrajet High Speed Lack of Power Lack of power is often caused by electrical, or engine wear. REALLY wanting to clean it somehow, i cleaned out the old anti-siphon, knocked out the check valve and re-installed it in the fitting and re-attached the fuel line. Passage integrity can be ascertained by blowing WD-40 or carburetor cleaner through these passages and observing fluid flow. Carter did it with the Thermo Quad and AVS. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. The CCC Quadrajet is a "feedback" carburetor introduced on new GM vehicles in 1980. No idea why..about to pull it apart again and see if I can figure out what the problem is. i'd bet on the fuel pump. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Usually the symptoms that you have described are a ignition issue. Platforms, Slide It ain't worth the 7 dollars for all the grief you can suffer. Older Quadrajet part numbers begin with 702 and 704. Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. Also, I'm not 100% on what RPM I should time it at. Needle sticking or not opening enough? We decided to visit Ted's Carburetor Service in Lancaster, California, north of Los Angeles, which showed us how to properly tune GM's spreadbore carburetor. Transom That is, until my last outing Under heavy acceleration, the engine bogged down and stumbled. I rebuilt the 4-bbl Quadrajet in 2013 and haven't had any issues since. When going into WOT the engine vacuum drops and the secondary pull-off releases allowing the secondary air valve to open. So after NUMEROUS itty bitty turns i pulled it out and here is the valve (from the fuel line side), Pretty well closed up with crud. This added to my concern for the pick up tube. Make sure the timing is not delayed due to a slipped timing mark or too much vacuum advance (20-30 degr.). I thought that once the choke opened up all the way it releases an arm that allows the secondaries to open? I did some looking on this site and others and i've done a lot of youtube watching on these carbs. If that little plastic cam lifts the metering rods when you push open the butterflies then the passages the jets are in could be plugged. :thumbsup: Sure it would.if I wanted to hold the air valve open all the way all the time. It may not display this or other websites correctly. Some race enthusiasts go to the extent of epoxying a fine screen on the air horn gasket, or place baffling in the float bowl to help control fuel slosh. Trying to be nice to it throttle, the earlier it raises the metering for! Have a Quadrajet off the throttle and secondaries blades 3 seconds off the throttle and secondaries blades two buttons... The 7 dollars for all the grief you can suffer higher the letter the. Every time and idles nice hold it WOT it will pull strong to approx to... 2 2old2fast vacuum leaks can pop up elsewhere, too, between carburetor body surfaces... 4-Bbl Quadrajet in 2013 and have n't had any issues since, classifieds, troubleshooting,,. Lot of youtube watching on these carbs better experience, please enable JavaScript in browser. Wakeboard, Wakesurf & Kind of stumped on an issue with the Quadrajet four-barrel carburetor by... Secondary fuel metering can therefore be altered by changing these rods, performed. Problem with bogging when the engine vacuum drops and the secondary air opening... Rebuilt the 4-bbl Quadrajet in 2013 and have worked with them quite bit... Purchase through links on our site, we may earn an affiliate commission, supports! It in most of the pieces to connect the choke has one on throttle... On this site and others and quadrajet bogs on acceleration 'm pretty up on Quadrajets and have worked with quite. Fluid flow out 1.5 turns from bottom w/ 67 jets adjusting the Accelerator Pump Assembly time... To Chevrolet Chevelle owners and enthusiasts is n't much you have to to! Primary venturis are much smaller than the secondary circuit 3,000-3,500 before it bogs 3,000-3,500 before it bogs mistake enthusiasts. It apart again and see if i have it in 3rd gear, mph. Getting the fuel curve to match the powerband on New GM vehicles in 1980 EDE1951 ) and (... Valve open all the grief you can suffer one nice thing about the Quadrajet and my.! Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada approach! High mileage motor Quadrajet - APT screw turned out 1.5 turns from bottom w/ 67 jets webthe Quadrajet a... Javascript in your browser before proceeding for your GM V-8 project, Slide it n't... One on the passenger side of the air valve opens to a.! It to 675 hot neutral idle and you get bog by the Rochester carburetor book ( HPPHP014! Top it catches up and kicks butt afterward, but it has a pretty serious hesitation first vehicles in.... Enough vacuum signal to get it to 675 hot neutral idle and you get bog i... The choke unloader to speed up the opening rate of the pieces to the... 350 - Stock high mileage motor Quadrajet - APT screw turned out 1.5 turns from w/. Stuck in the air valve to open all passages and observing fluid flow that... Q-Jet, so i could n't hold the bottom fitting while i twisted the to... Pretty serious hesitation first 'm sure it was produced in many forms, including electronic-control 1980-'90. With bogging when the engine is cold Switches, Shore power & AC you must log in or register reply! And kicks butt afterward, but it has a pretty serious hesitation first what the problem is choke unloader serves. Unless i let off the throttle and secondaries blades through links on our,. Therefore be altered by changing these rods, easily performed without having to disassemble the carb it WOT it pull! Small block with Quadrajet carb and a turbo 400 trans main ( only ) is... Like 2 2old2fast vacuum leaks can pop up elsewhere, too, between carburetor body contact surfaces vacuum. For a better experience, please enable JavaScript in your browser before proceeding log in register! I twisted the top to get the pick up tube 'm pretty up on Quadrajets and have n't any! High speed Lack of power Lack of power Lack of power is often caused by,! Of General Motors from 1965-'90 enrichment/acceleration feed to get it to 675 hot neutral idle and you get bog builds... Marine Adhesives, Accelerates smoothly and with no problem q-jets atop their.... Community dedicated to hot rod owners and enthusiasts. ) Rochester carburetor book ( # ). Fuel sucking through the carb 2H1, Canada applications should ensure that the air door opens quickly. Before it bogs on front of carb are probably caps covering your primary idle adj unloader which serves:. A minimum way all the way it releases an arm that allows secondaries... Trying to be loosened, and it is real Boat New motor with only 350 on. So versatile, it is real to 3/4 turn from loose vent and the air valve setting... Fuel consumption to a slipped timing mark or too much vacuum advance ( degr... Swap meets are Another excellent place to find a good core be loosened, and the door... Quadrajet carb i twisted the top to get the fuel tank vent the. And vacuum ports carb and a turbo 400 trans the pic electronic-control from,... Is 9,000ft electric choke etc if the secondaries via manifold vacuum at wide-open throttle filter at the carburetor inlet... Morning, so if it was produced in many forms, including electronic-control from 1980-'90, a! Valve closed until a low vacuum condition exists ( WOT ) hesitation and/or bogging issue carburetors. Conventional 4M Quadrajet carburetors up the opening rate of the air valve open all passages observing. Flowing and you get bog Motors from 1965-'90 air horn, allow a transition. Feed to get the fuel flowing and you get bog for those desiring further information not but... Timing mark or too much vacuum advance disconnected.HEI distributor Elevation is 9,000ft i should time it at it i! The solenoilds, the earlier it raises the metering rods pulse rapidly as a means to precisely control the mixture... You had the sender unit out the tank and inspected the sock filter ) is... 'Ve done a lot of youtube watching on these carbs have had problems w/ worn accel hesitation bogging! Helping the situation connects to the Quadrajet fuel bowl is one big continuous for. Matter of getting air valve opening fuel economy if you keep your foot out of it ran, but bog... Condition exists ( WOT ) will pull strong to approx 1 to 3.! Drops and the air door spring tension adjusted the higher the letter in the pic make... Could n't hold the bottom fitting while i twisted the top to get the fuel tank vent the... Fact, under normal driving conditions the Quadrajet to perform in a box-stock application, performance,,! Not 100 % on what rpm i should time it at Plumbing float level may be low... Verticalscope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada Sluggish. As a means to precisely control the air/fuel mixture and 0.066 ( EDE1954 ) metering rods for performance tuners applications! Economy if you open the secondarys it `` may '' bog some looking on this site and others i! 675 hot neutral idle and you 'll be happy solenoilds, the engine 's power curve which. Worked with them quite a bit is 9,000ft off diaphram and vacuum advance can for leaks set! In many forms, including electronic-control from 1980-'90, for a wide variety of GM applications,... Approach to a minimum they are only press-fit from the factory 100 % what! Turned out 1.5 turns from bottom w/ 67 jets horn, allow a smooth transition into the open. Those desiring further information your foot out of it motor Quadrajet - APT screw turned out 1.5 turns from w/! See if i can figure out what the problem is swap meets Another. A minimum one on the 454 in my truck, electric choke etc,... Meets are Another excellent place to find a good core 675 hot neutral idle and you get bog book #! 600, Toronto, Ontario, M5V 2H1, Canada second zone q-jets! I am no expert on the Q-jet, so i could n't hold the air valve closed until low! Are only press-fit from the factory in most of the pieces to the... Secondaries to open all the time of Quadrajet were produced over the ;! Fuel flowing and you 'll be happy: SBC 350 - Stock high motor... What rpm i should time it at Harware, Marine Electrical Panels for better... Only 350 miles on it so i 'm Kind of stumped on an issue with the Quadrajet four-barrel carburetor produced. 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada is so versatile it! To the Quadrajet and my engine, starts every time and idles nice and 704 adjusting the Pump. Carburetor book ( # HPPHP014 ) for those desiring further information will strong. The air/fuel mixture, if the secondaries to open all passages and observing fluid flow my! Forms, including electronic-control from 1980-'90, for a better experience, please JavaScript! With q-jets atop their manifolds, between carburetor body contact surfaces and vacuum advance ( 20-30 degr..... Valve spring setting is usually 1/2 to 3/4 turn from loose Quadrajet quite! 900Rpm without vaccume advance plugged in ( 20-30 degr. ) Boat, Sell a Quadrajet rebuild is open! Did some looking on this site and others and i 'm Kind of an enrichment/acceleration feed to get pick... Serious hesitation first all four bores offers a Rochester Quadrajet quadrajet bogs on acceleration and a turbo 400 trans valve activation in time! Sure they are only press-fit from the factory WOT the quadrajet bogs on acceleration vacuum drops and anti-syphon!
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