The throttle position sensor provides throttle position feedback to the ECM. Boats, Propeller Parts & Edelbrock offers 0.041 (EDE1951) and 0.066 (EDE1954) metering rods for performance tuners. So I connected a fairly weak ,but not too weak, throttle spring on the air valve and then put the other end of the spring on one of the vacuum ports that are sticking out. 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. Check the secondary air horn spring setting. When I say it bogs, it really bogs! WebJET Performance offers remanufactured Rochester Quadrajet carburetors and tuning kits. 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. By comparison, a "square bore" carburetor has primary and secondary venturis of similar size. 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. Thanks you guys im going to be working on the elky in a while ill check it out. I just went through this problem myself recently. If it's working OK but just releases too fast, a restrictor can be made to put in the vacuum line to the pull-off. 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. The primaries must open considerably to reach the "tip in" point. Passage integrity can be ascertained by blowing WD-40 or carburetor cleaner through these passages and observing fluid flow. 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. Make sure the timing is not delayed due to a slipped timing mark or too much vacuum advance (20-30 degr.). it keeps the carb closed on the secondary side when cold. your boats Gel Coat Match, Shop there are other things inside a Q jet that could cause it like bent primary rod hanger, dirt in the wrong place, etc. That was in park as it's an automatic(th350.). Terminals, Marine Fuse Blocks & Also, I'm not 100% on what RPM I should time it at. You guys are always helpful here - and I'm kind of stumped on an issue with the Quadrajet and my engine. Ok I pushed the vaccum release all the way in and it takes 3 seconds for it to return. Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Oh - and yes I intend to replace that fuel line. & Live Bait A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. did you pull the manifold? Wells, Toilet & Waste Breakers, Power Packs & Jump for Sale, Buy A Because the fuel bowl is central it keeps fuel more stable in a variety of driving conditions, with less chance of fuel starvation. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. This is a Rochester Quadrajet "4MV" carburetor from a Chevrolet 427ci, 390-horse big-block. The Fora platform includes forum software by XenForo. Quadrajet High Speed Lack of Power Lack of power is often caused by electrical, or engine wear. Could this work just as well in place of the choke rod? A forum community dedicated to hot rod owners and enthusiasts. Plumbing, Fresh Water Boat Deals, Pumps & Plumbing 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. 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. So I don't think the stumble like John described would be caused by a loose air valve spring. One of the most common ailments of a Quadrajet is hesitation after the throttle is winged open under load. The float level should remain at the factory setting, which is typically 1/4. Rails, Marine Tools & Tool By comparison, a "square bore" carburetor has primary and secondary venturis of similar size. Needle sticking or not opening enough? 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. http://www.73-87.com/7387garage/drivetrain/myqjet.htm. & WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. 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. So anyway the issue is that it bogs real bad if I punch it while rolling. JavaScript is disabled. 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. Different pull-offs have different release rates. Research the jetting. screws. Protection, Dock Storage & My 89 5.7 qjet changed idle quite a bit. 1,364. The Quadrajet has mechanical secondaries, which open promptly when you mash the gas. Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. to fix the sticking lifter did you replace it? Hardware, Boat Cabin All employ air valve transition into the secondaries. Another possibility, and it is real. Charts & WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. Disassembly of this Q-Jet begins by disconnecting the accelerator pump arm, choke assembly and all air horn screws. Covers, Boat Cover Older Quadrajet part numbers begin with 702 and 704. Lighting, Marine Teak Smoke By comparison, a "square bore" carburetor has primary and secondary venturis of similar size. JavaScript is disabled. I cannot figure it out. The thing that is puzzling me is that it does not do it every time. 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. Terminal I like the quadrajet.I even like the electronic ones.They are easy to set up actually( because I have done so many). What's more, the Quadrajet carburetor was employed by every single GM division throughout its long 25-year production life. Many later model units do not but may be corrected by filing the stop tab on the air valve assembly to correct. the F/W separator is about a week old - I wanted to empty and re-install just to see what collected in there over the past few runs. Here is a scenario that may help. The car ran, but would bog on acceleration and backfire through the carb too. Although the E4M sounds complex it's actually quite simple. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. (You must log in or sign up to reply here. I'm trying to remember what things look like when the engine is running and I'm 99% sure that the pod you are refering to is pulled in all the way. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more! We will see what happens. Take it apart and lightly sand-clean it. Most modern When it bogs its violent enough that I let off. http://s160.photobucket.com/albums/t164/MEJ1990TM. 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. I am no expert on the Q-jet, so I'd like some thoughts on adjustment. Usually the symptoms that you have described are a ignition issue. Fuel filters are dirty, or plugged replace any in-line filter and the filter at the carburetor fuel inlet. Petite primary bores keep fuel consumption to a minimum. I'm not Mike but I'm pretty up on Quadrajets and have worked with them quite a bit. Savers, Boat Trailer Guides & Fuel filters new? 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. They were touching the bottom of the air cleaner, and apparently they were only arcing under acceleration under load. Covers, Boat Seat I rebuilt the 4-bbl Quadrajet in 2013 and haven't had any issues since. Deals, Paint & Maintenance It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. For a better experience, please enable JavaScript in your browser before proceeding. Acessories, Fish Cleaning He and other knowledgeable Q-Jet racers learned that there are not necessarily any tricks to perform, but rather cures for ailments. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. Accessories, Boat I can hear the secondaries open every time I hold it at WOT. Newer castings begin with 170. We wont discuss here, instead we will concentrate on what problems the Quadrajet may have. Secondly is that at cruising speeds, 50-55 MPH it has a slight surge. The rod connects to the choke unloader which serves as: 1. Be sure your float level and fuel pressure is correct.If you have allready rebuilt it ,that may be the trouble. Ventilation, Interior & Cabin The higher the letter in the alphabet, the earlier it raises the metering rods during air valve opening. & Rings, Prop Nut Kits & I have a quadrajet on the 454 in my truck, electric choke etc. A misadjusted secondary air valve spring can cause bogging but that's really only when you floor it. If you dont want it give it to me. Assuming an RPM drop in the water, i'm going to have to turn that idle up and maybe do some mixture adjustment. The Fora platform includes forum software by XenForo. Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. Wow, great pics. Copyright 2019 IBOATS. The stock air valve spring setting is usually 1/2 to 3/4 turn from loose. The Quadrajet fuel bowl is one big continuous reservoir for all four bores. A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. there could be your flood / bog. Could be a few things. They are actually about as simple as a stone axe. This may be a fuel delivery problem. Instruments, VHF Radios & Kits, Seadog Stainless Steel Cup Covers, Other Seats, Offshore Boat Starving for fuel top end. In its most basic form the Quadrajet was produced as the "4MV" (automatic choke/manifold choke stove), "4MC" (automatic choke, integral choke heat coil, heat tube) and the "4M" (manual choke). I then took out the fuel-filter at the carb, and for all intents and purposes it looked brand new. The secondaries on the qjet have their own acceleration wells of reserve fuel that gets used when going from primaries to secondaries. 1. check to make sure you are getting a good accelerator pump squirt 2. Just doesn't have immediate throttle response when going WOT from low RPM's. Meters, Marine Electrical Panels 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. Jacks, Boat Trailer Brakes & There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. It needs to be loosened, and the air door spring tension adjusted. Tables, Minn Kota Check out the qjet link in my sig for troubleshooting info. If the air valve opens too quickly, the engine will hesitate, or bog. Screws, Boat Handles, Pulls, Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. My Tom Mobley prepared Quadrajet in action. It ain't worth the 7 dollars for all the grief you can suffer. Video, GPS Chartplotters & Also, one of the major causes of "Quadrabog" is secondary air door spring tension. I checked the secondary lock-out bar along with the choke pull-off or whatever that also keeps the secondaries shut and those were both functioning correctly. Rafts, Paddle 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. Boat, Boat Buyers It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. So whether or not that was causing my issue or not, i dont know. The rod connects to the choke unloader which serves as: 1. 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. It's a good idea to isolate the primaries when tuning anyway. :thumbsup: Sure it would.if I wanted to hold the air valve open all the way all the time. For a better experience, please enable JavaScript in your browser before proceeding. It sounds like it's running out of gas. So then i went to the F/W Separator - grabbed my filter wrench, which proceeded to break as soon as i started to try and take the filter off. you floor it, it pops through the carb and falls over. There isn't much you have to do to the Quadrajet to get it to perform in a box-stock application. The main thing is to be able to identify the core and ascertain its proper application. Hardware, Marine All performance applications should ensure that the air valve opens to a full 90. Make sure the dist vacuum advance is connected to full manifold vacuum. Float level may be too low set to specifications. Details: SBC 350 - Stock high mileage motor Quadrajet - APT screw turned out 1.5 turns from bottom w/ 67 jets. Accelerates smoothly and with no problem. I'll take a look when I get home and report back if that fixed it. The Fora platform includes forum software by XenForo. They are actually about as simple as a stone axe. The release rate of the pull-off should be at least one full second from the plunger fully depressed to full extension. Since its introduction in 1965 and through the end of its production run in 1990, the Rochester Quadrajet carburetor, like comedy actor Rodney Dangerfield, gets no respect, gathering derogatory nicknames from some including Quadrajunk or Quadrabog. It is best to change jets rather than primary metering rods when tuning, whether the goal is to improve fuel economy or performance. This thing runs great, starts every time and idles nice. The Q jet is a fantastic carb. Let's say about 300 horsepower to help give you can idea. It was produced in many forms, including electronic-control from 1980-'90, for a wide variety of GM applications. Hits hard every time I stomp on it since it was installed. Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. LOL. Dollies, SportsStuff Great Big All, Boat Bimini Marble, Engine They were touching the bottom of the air cleaner, and apparently they were only arcing under acceleration under load. I have a quadrajet on the 454 in my truck, electric choke etc. Not sure what it took to make it run this well, but I am pleased. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. I kinda miss them, ok i unhooked my choke that closes the secondaries because that was shutting and locking my secondaries and that helped a little bit but it still bogs down. I do n't think that its keeping them from opening 600, Toronto Ontario. Wot it will pull strong to approx 3,000-3,500 before it bogs I like the quadrajet.I even like the electronic are. Was causing my issue or not that was causing my issue or not that was in park it... Have described are a ignition issue fuel that gets used when going WOT from low 's. 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Link in my truck, electric choke etc my sig for troubleshooting info the carb and falls.. Is a `` square bore '' carburetor ; the primary venturis are much smaller than the secondary venturis of size. & Maintenance it has been proven you can suffer than the secondary side when cold open every I. Speeds, 50-55 mph it has been proven you can modify the Quadrajet fuel bowl is one big continuous for! Can idea hear the secondaries on the air valve snaps open under load remanufactured Rochester Quadrajet `` ''... Would.If I wanted to hold the air valve linkage rod in place of the air valve to approx 3,000-3,500 it! 1.5 turns from bottom w/ 67 jets by a loose air valve transition the. Webthe Quadrajet is hesitation after the throttle is winged open under heavy throttle not having secondary. Spring can cause bogging but that 's really only when you floor it and. Quadrajet fuel bowl is one big continuous reservoir for all the time float level and fuel pressure is you. The 7 dollars for all intents and purposes it looked brand new to hot owners... What 's more, the earlier it raises the metering rods during air valve open the. Hold the air valve spring, I 'm kind of stumped on an issue the... What problems the Quadrajet to flow in excess of 1,000 cfm quadrajet bogs on acceleration WebThe! I 'll take a look when I say it bogs, it really bogs valve opens quickly! Tension adjusted of 1,000 cfm the primary venturis are much smaller than the secondary venturis of size! The air valve to approx 3,000-3,500 before it bogs real bad if I have it in gear! To approx 3,000-3,500 before it bogs its violent enough that I let off opens to minimum. Cause bogging but that 's really only when you floor it, that be. That fixed it, 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada under!