quadrajet bogs on acceleration

All, Anchor & Parts, Boat Tubing & Accelerates smoothly and with no problem. Fuel pick up in the tank? The thing that is puzzling me is that it does not do it every time. It's easy to check. Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). Vacuum leaks can pop up elsewhere, too, between carburetor body contact surfaces and vacuum ports. WebEp: 25 in this video I show how to fix a hesitation and/or bogging issue with carburetors by adjusting secondaries. You can modify the choke unloader to speed up the opening rate to 1 to 1 1/2 seconds. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. WebJET Performance offers remanufactured Rochester Quadrajet carburetors and tuning kits. When you study the Quadrajet's architecture it's apparent it has nothing in common with Holley-based carburetor designs. I know the pod that you are talking about but that is it. Deals, Electronics A forum community dedicated to hot rod owners and enthusiasts. Maintenance, Pumps and Boat Repair, Boat Paint & It may not display this or other websites correctly. If the air valve opens too quickly, the engine will hesitate, or bog. You are using an out of date browser. The pull-off is connected by a linkage rod. Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). Webtypes of bog: the first is bog when the vehicle is accelerated from a stop; the second is bog when the vehicle is accelerated from cruise. The choke unloader opens the choke to a certain opening when manifold vacuum is applied at engine start. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. Jan 19, 2011. Good for the interstate cruise. Locks, Boat Deck H-P Books offers a Rochester Carburetor book (#HPPHP014) for those desiring further information. Terminal Any ideas? If I step on it from part-throttle/low rpm's it bogs pretty hard and sometimes even dying. They are notorious for leaking since they are only press-fit from the factory. I can't say what it does after a few seconds. Holder, Anchor & Dock Authentication and pre-purchase inspection service still available. All rights reserved. The secondaries on the qjet have their own acceleration wells of reserve fuel that gets used when going from primaries to secondaries. & Live Bait If the secondaries open too fast there is not enough vacuum signal to get the fuel flowing and you get bog. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! Ropes, Boat Primary jet size is commonly in the 0.068 to 0.075 range. While there are other issues that may cause similar reactions within the carburetor, often the problem can be traced back to the accelerator pump system. When the motor is warm it hesitates but barely. The one on before that lord only knows how long it was in there. to fix the sticking lifter did you replace it? Secondly is that at cruising speeds, 50-55 MPH it has a slight surge. 1,364. Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. I've tried adjusting timing, hasn't changed anything. Is it a good stream like you'd piss after drinking 3 PBR's? Towers, Tow Ropes & Try it fast and slow and watch the stream of fuel. Professionals. Daytona Beach, FL. JavaScript is disabled. JavaScript is disabled. The Quadrajet's basic design didn't change much over its 25-year production life with the exception being the introduction of APT (Adjustable Part Throttle) in 1968 and electronic mixture control later. Drink Holders, http://www.marinepartssource.com/new0Fuel%20Filter, http://discountmarinesource.com/p-52847-sierra-in-line-fuel-filter-7855.aspx. Breakers, Power Packs & Jump What's more, the Quadrajet carburetor was employed by every single GM division throughout its long 25-year production life. 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. Harware, Marine Nuts, Bolts, & It's a QuadraJet. We will see what happens. Deals, Electrical The Q jet gets a bad rap from being misunderstood. He and other knowledgeable Q-Jet racers learned that there are not necessarily any tricks to perform, but rather cures for ailments. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. 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. Combos, Fishing Tools & Although the E4M sounds complex it's actually quite simple. Another possibility, and it is real. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more! Unless I let off the throttle, the engine would die. For a better experience, please enable JavaScript in your browser before proceeding. There isn't much you have to do to the Quadrajet to get it to perform in a box-stock application. For a better experience, please enable JavaScript in your browser before proceeding. Copyright 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Motors, Fishing Downriggers & Now, Shop Following all of these procedures and doing a thorough rebuild will certainly wake up any Quadrajet. During recent runs, engine bogs at 2500 rpm (normal WOT is about 4000), starts to choke a little. Manufacturer, Boat Tables & Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. It poured out some nastiness and i couldn't find a brand name or part number on it - but it listed ALL of the compatible filters from every other company. Be sure your float level and fuel pressure is correct.If you have allready rebuilt it ,that may be the trouble. It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. also accel. http://forums.highperformancepontiantiac/quadrajet-secondary-accelerating-wells/. Unless I let off the throttle, the engine would die. Maybe the choke is open too far? Webtypes of bog: the first is bog when the vehicle is accelerated from a stop; the second is bog when the vehicle is accelerated from cruise. 1160 hours on engine. Remanufactured stock replacement and high-performance units are still readily available from a variety of sources, including JET Performance Products (JET). Delco-Rochester produced three different sized inlet valves: 0.110, 0.125, and 0.135. However, you're not going to need that much flow for great street/strip performance. When adjusting engine idle, it is important that the primary throttle blades remain in line with the throttle body transfer slots, or performance, fuel economy, and driveability will suffer. & Rings, Prop Nut Kits & Honda 5hp Outboard, Boat I then took out the fuel-filter at the carb, and for all intents and purposes it looked brand new. It's a QuadraJet. No power at all and will chirp the rear tires from compression lock! I like the quadrajet.I even like the electronic ones.They are easy to set up actually( because I have done so many). 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. Webtypes of bog: the first is bog when the vehicle is accelerated from a stop; the second is bog when the vehicle is accelerated from cruise. I fixed the needle retaining clip and was playing around with the accelerator pump and noticed I'm only getting one stream of fuel on the left(passenger) side. Disassembly of this Q-Jet begins by disconnecting the accelerator pump arm, choke assembly and all air horn screws. The air valve is controlled by both return spring tension and the vacuum break diaphragm, which through engine vacuum, restricts and slows the opening. Just doesn't have immediate throttle response when going WOT from low RPM's. This design is not unique to the Quadrajet. The idle is set at 900rpm without vaccume advance plugged in. Biminis, Paint and When you purchase through links on our site, we may earn an affiliate commission, which supports our community. The stock air valve spring setting is usually 1/2 to 3/4 turn from loose. As the secondary throttle valve opens, the air valve begins to open as well. GPS Chartplotter and Fish Finder Combo, Find I'm not sure I understand what you are talking about with release rate of the pull off? Small-blocks through 350 ci are happiest with 750 cfm. The Quadrajet has mechanical secondaries, which open promptly when you mash the gas. Subsequently, it is extremely unlikely that new units will ever be produced again. Furniture, Boat Seat Pedestals & The boat is going out early Saturday morning, so if it was just the valve and all works, then sweet. Yours should be around 2 seconds. The late John Lingenfelter, a legendary drag racer and engine builder, was among the first to turn the Quadrajet into a record-setter on his Super Stock Chevys in the early 1970s. JavaScript is disabled. I vote for a worn accelerator pump in the carb. The thing is, the motor was not bogging before and the only thing that has changed since is the timing and the APT screw along with a lifter sticking. Biminis, View screws. I thought that was it? Communication, Auto Pilot It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. it is a small pin on the passenger side of the carb. where is the fuel filter and how old is it? I fixed the accelerator pump and started it but it was still bogging. ball could be your culprit. Software, Digital Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. Seats, Pontoon Boat Seats & it's all the way out in the pic. Tackle Boxes, Fishing Bait & Parts, Rule 1500 GPH Automatic 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. your boats Gel Coat Match, Shop Shop Helm Seats, Shop Neither of which had the previous setting checked which was stupid on my part. The mechanic gods were not in with me last night obviously. So I don't think the stumble like John described would be caused by a loose air valve spring. Most performance applications utilize rods with power tips in the 0.030 to 0.050 range. Oars, Wakeboard, Wakesurf & And, here is what i see pretty ugly - but most of what was there wiped away - just crud built up from washes/water it appears. 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. 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. A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. This is where you need to modify your Q-Jet's fuel metering and air valve function in order to keep up with engine upgrades. Because the fuel bowl is central it keeps fuel more stable in a variety of driving conditions, with less chance of fuel starvation. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! CREATE Air horn removal allows access to the fuel metering rods, fuel bowl and throttle body. WebEp: 25 in this video I show how to fix a hesitation and/or bogging issue with carburetors by adjusting secondaries. Tables, Minn Kota Sealant, & I don't think your problem is the carburator. During recent runs, engine bogs at 2500 rpm (normal WOT is about 4000), starts to choke a little. 1,364. Enthusiasts either love it or hate it. http://www.73-87.com/7387garage/drivetrain/myqjet.htm. the pin in the throttle rod for the secondaries might not be keeping the secondaries closed. 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. ive got a 350 bored .30 over rv cam flat tops / milled polished heads/ 10.25.1 compression with a QUADRABOG and it lives up to its name when i floor it and get the secondaries to open up it bogs down any ideals? Tubes, Shop It has more in common with the Carter Thermo Quad and AVS carburetors because it employs main metering rods and a secondary air valve, which makes it function very different than a Holley. Newer castings begin with 170. Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Wow, great pics. Take the air cleaner off the carb and with the engine turned off, run the throttle linkage through it's travel while looking down the carb throat. The Fora platform includes forum software by XenForo. I have a freshly rebuild LS5 which is stock other than a Voodo 60203 cam and a MSD ignition. I had both of these problems at once. When a Quadrajet is installed in a stock application it's operating in the environment it was designed for. Hardware, Boat Seats by The check valve side wasn't bad. To this day, many record-holding Super Stock cars run well into the nine second zone with Q-Jets atop their manifolds. Quadrajet High Speed Lack of Power Lack of power is often caused by electrical, or engine wear. But then again, that side doesn't half fuel sitting it in most of the time. I have a quadrajet on the 454 in my truck, electric choke etc. Now that I'm undrstanding this a bit better I can give you a little more info. Fuel filters are dirty, or plugged replace any in-line filter and the filter at the carburetor fuel inlet. When the motor is warm it hesitates but barely. For a better experience, please enable JavaScript in your browser before proceeding. I have a quadrajet on the 454 in my truck, electric choke etc. This is a Rochester Quadrajet "4MV" carburetor from a Chevrolet 427ci, 390-horse big-block. i'd bet on the fuel pump. The Bog simply means the engine is not receiving enough fuel when you go to wide open throttle. Fuel filters are dirty, or plugged replace any in-line filter and the filter at the carburetor fuel inlet. Vinyl, Floating Boat Let's say about 300 horsepower to help give you can idea. The Fora platform includes forum software by XenForo. If you run a CCC Quadrajet on a non-CCC engine you will wind up with an overly rich fuel mixture and horrid performance because there's no way to regulate the air/fuel mixture. 02. So i couldn't hold the bottom fitting while i twisted the top to get the pick up out. This may be a fuel delivery problem. Another method of rectifying this is by drilling a small hole in each primary throttle blade to lean the engine a bit at idle. 3 things I'd check John: ( other than a big vaccum leak which would do this). 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. That would make sense when cold. did you pull the manifold? The downside to older Quadrajet cores is abuse and core shift. If you dont want it give it to me. Too many of us give up because this carburetor requires time, knowledge and patience. 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. At heavy throttle, manifold vacuum goes away and the unloader relaxes, allowing the air valve to open via the linkage rod. They are actually about as simple as a stone axe. You must log in or register to reply here. Ventilation, Interior & Cabin Also, I'm not 100% on what RPM I should time it at. In fact, under normal driving conditions the Quadrajet performs quite well. Holders, Cabin Accessories & for Sale, Buy A On on end of the secondary air door shaft, on the underside, is a small clamp screw. The CCC Quadrajet is a "feedback" carburetor introduced on new GM vehicles in 1980. The hole in the restriction should be about .018-.020. Kind of an enrichment/acceleration feed to get the fuel sucking through the secondary bores. Kind of an enrichment/acceleration feed to get the fuel sucking through the secondary bores. The secondaries on the qjet have their own acceleration wells of reserve fuel that gets used when going from primaries to secondaries. Have you had the sender unit out the tank and inspected the sock filter? Despite the Quadrajet's reputation for frustrating tunability, it is a great performer when it is properly assembled and tuned. I'd think that if it were nosing over due to the secondaries opening too fast ,that it would catch up after a couple seconds. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Login, Boats For most street and weekend race applications you can to get by with 750-800 cfm without breaking a sweat. Charts & Fuel slosh within the float bowl is yet another issue that needs to be scrutinized, particularly on hard-leaving drag cars. 1160 hours on engine. The Fora platform includes forum software by XenForo. If you open the secondarys it "may" bog? 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. But, I'm sure it wasn't helping the situation. Depending on what/who's kit you got for the rebuild,it's possible that the needle/seat opening is too small to feed the small QJ bowl. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. It controls the air door, if the air door opens too quickly it will hesitate. New motor with only 350 miles on it so I'm trying to be nice to it. Jacks, Boat Trailer Brakes & Few realize that the Q-Jet has a strong racing heritage, particularly in NHRA Stock and Super Stock drag racing where an OEM carburetor is required. Deals, Dealer (You must log in or sign up to reply here. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. Boat, Boat Buyers Make sure the secondary accelerator wells are filling. Take it apart and lightly sand-clean it. There may not be any correlation between the cam change and the current bog. I wouldn't sweat that idle speed change. Winches, Boat Motor Supports & The fuel metering solenoid gets a rapid pulsing signal from the ECM (electronic control module), which pulses based on power demand and exhaust gas oxygen content. Going to a rod with a smaller power tip, for example, will richen the mixture, while a larger power tip will lean the engine. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. General Motors developed the Quadrajet as an economy carburetor with the added twist of available performance. Quadrajet High Speed Lack of Power Lack of power is often caused by electrical, or engine wear. Accessories, Big Jon A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. The new fuel pump just may not be up to the job anymore. Dock, Cabin and Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. Research the jetting. That's the best all around deal. I am no expert on the Q-jet, so I'd like some thoughts on adjustment. When it bogs its violent enough that I let off. For this reason, it is vital that a true, high-volume fuel pump be in place along with fuel lines that are properly sized to meet the engines fuel demands. I just went through this problem myself recently. When depressing the butterfly it resists a little bit. Check out the qjet link in my sig for troubleshooting info. 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.

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