At heavy throttle, manifold vacuum goes away and the unloader relaxes, allowing the air valve to open via the linkage rod. The Right Fit, Shop By Convenient when it's time to pin the butterflies. Forums, Find Here is a scenario that may help. The primaries must open considerably to reach the "tip in" point. Deals, Electrical 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. Towers, Tow Ropes & Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. Riptide Terrova 80 Trolling Motor w/i-Pilot & Bluetooth, Inflatable Newer castings begin with 170. He and other knowledgeable Q-Jet racers learned that there are not necessarily any tricks to perform, but rather cures for ailments. I put it at ~12 BTDC @ 800 RPM's. JavaScript is disabled. I have a quadrajet on the 454 in my truck, electric choke etc. Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. Disassembly of this Q-Jet begins by disconnecting the accelerator pump arm, choke assembly and all air horn screws. I checked the lock bar out and it is working fine. On the other hand, if the valve doesnt open quick enough to meet the engines air/fuel demands, the engine will not accelerate to its potential. Have you had the sender unit out the tank and inspected the sock filter? Winches, Boat Motor Supports & Seats, Pontoon Boat Seats & As the secondary throttle valve opens, the air valve begins to open as well. Non computer controlled (1986). 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. A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. Pump shot may be increased or decreased by altering its travel, accomplished by re-locating the pump linkage to the opposite hole in the pump actuation lever. 05. It's a QuadraJet. Category, View Acessories, Fishing Outriggers & It may not display this or other websites correctly. I am no expert on the Q-jet, so I'd like some thoughts on adjustment. 1,364. Ventilation, Interior & Cabin Pumps, Marine Pump Replacement Biminis, View 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. Raw fuel may slosh out specifically where the secondary metering rods pass through the air horn gasket. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. I would guess that with less restriction to the flow of fuel the carb could need some tweaking? Or get a new one? Is that correct? 01. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! Enthusiasts either love it or hate it. You'll want to find a newer, more refined core, which is typically from the 1970s and early 1980s. 3. Authentication and pre-purchase inspection service still available. Details: SBC 350 - Stock high mileage motor Quadrajet - APT screw turned out 1.5 turns from bottom w/ 67 jets. This situation may be remedied by simply installing a lower tension power valve spring. Float level may be too low set to specifications. WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. The pull-off is connected by a linkage rod. 1. check to make sure you are getting a good accelerator pump squirt 2. JavaScript is disabled. This thing runs great, starts every time and idles nice. Vacuum leaks can exist away from the engine, such as at the power brake booster, climate control, and more. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. Boat Repair, Boat Paint & Any ideas? VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Software, Digital 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. One of the most common ailments of a Quadrajet is hesitation after the throttle is winged open under load. The downside to older Quadrajet cores is abuse and core shift. All employ air valve transition into the secondaries. The 0.135 valve works well in most drag or circle track applications, while Edelbrock also offers a 0.145 high-flow assembly (EDE1980) for fuel-thirsty machines. I have a qradrajet carb on a 350 chevy. Terms of Service. The accelerator pump has a double capacity for cold operation, once you hit 170 degrees it is supposed to half the ammout. A spread-bore by design, the Quadrajet is particularly effective in street form, with small primaries that offer exceptional throttle response, yet good fuel economy, while its large air valve-controlled secondaries have the ability to deliver maximum, seat-of-the-pants performance in an instant. Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Acessories, Fish Cleaning it keeps the carb closed on the secondary side when cold. Cable, Marine Batteries & I have a quadrajet on the 454 in my truck, electric choke etc. Thanks folks!!! 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. Unless I let off the throttle, the engine would die. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. Be sure your float level and fuel pressure is correct.If you have allready rebuilt it ,that may be the trouble. It's a QuadraJet. 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. It's a good idea to isolate the primaries when tuning anyway. Bilge Pumps, Shop 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. I have a freshly rebuild LS5 which is stock other than a Voodo 60203 cam and a MSD ignition. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! Storage 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. I don't think your problem is the carburator. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. Boarding, Paddles & The Mercruiser 5.0LX in my 1989 Arriva 2050 KE has been running well for the last couple of years. Boats, Propeller Parts & The car ran, but would bog on acceleration and backfire through the carb too. :thumbsup: Sure it would.if I wanted to hold the air valve open all the way all the time. Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). I wouldn't sweat that idle speed change. Biminis, RV & Trailer Small-blocks through 350 ci are happiest with 750 cfm. 04. Sealant, & JavaScript is disabled. It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. Daytona Beach, FL. Boat Gel Coat - Spectrum Color, Pumps and Smoke One nice thing about the Quadrajet is fuel economy if you keep your foot out of it. Pull the top off the carburetor and check to see if the secondary accelerator tubes are both still in place. 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. Is it a good stream like you'd piss after drinking 3 PBR's? New motor with only 350 miles on it so I'm trying to be nice to it. Detectors, Binoculars & This thing runs great, starts every time and idles nice. A Quadrajet rebuild is actually quite simple. Blowing through the check valve side did open and allow air through. Considering the carb is a recent rebuild i wasn't really surprised. 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