Guide, Boat Dock, Cabin and Systems, Marine Plumbing I have a freshly rebuild LS5 which is stock other than a Voodo 60203 cam and a MSD ignition. Covers, Boat Cover Manufacturer, Boat Tables & Video, GPS Chartplotters & Following all of these procedures and doing a thorough rebuild will certainly wake up any Quadrajet. Biminis, RV & Trailer Daytona Beach, FL. 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. Let's say about 300 horsepower to help give you can idea. Delco-Rochester produced three different sized inlet valves: 0.110, 0.125, and 0.135. 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 Quadrajet four-barrel carburetor was produced by the Rochester Carburetor Division of General Motors from 1965-'90. Yours should be around 2 seconds. A forum community dedicated to hot rod owners and enthusiasts. Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Be sure your float level and fuel pressure is correct.If you have allready rebuilt it ,that may be the trouble. your boats Gel Coat Match, Shop This situation may be remedied by simply installing a lower tension power valve spring. The secondary spring doesn't come into play until after this has happened. John, that isn't by any chance Escondido, California is it? You must log in or register to reply here. WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. JavaScript is disabled. Check it when cold and hot. Daytona Beach, FL. Newer castings begin with 170. & Circuit "Quadrabog," "Quadrajunk," and a host of other time proven nicknames define GM's most notorious four-barrel carburetor. Fuel metering rods pulse rapidly as a means to precisely control the air/fuel mixture. I fixed the accelerator pump and started it but it was still bogging. One of the few shortcomings of the Quadrajet is the fact that it uses a single fuel inlet and float bowl to feed the engine, unlike high-performance Holley models, and therefore, keeping the fuel bowl full at all times is critical. They are actually about as simple as a stone axe. Check the fuel tank vent and the anti-syphon check valve. Accessories, Pontoon Bimini Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. Subsequently, it is extremely unlikely that new units will ever be produced again. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. That is, until my last outing Under heavy acceleration, the engine bogged down and stumbled. try wiring the secondaries shut to see if that solves the problem. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! For a better experience, please enable JavaScript in your browser before proceeding. The Mercruiser 5.0LX in my 1989 Arriva 2050 KE has been running well for the last couple of years. JavaScript is disabled. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. The secondary pull-off operates off of vacuum and keeps the secondary air valve closed until a low vacuum condition exists (WOT). When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Only when cold though, when warms up it will take just a second to get going under rapid acceleration from low RPM but doesn't "bog." 9000 feet is pretty high. This thing runs great, starts every time and idles nice. where is the fuel filter and how old is it? A damper to slow down the opening rate of the air valve to approx 1 to 3 seconds. Oars, Wakeboard, Wakesurf & You are using an out of date browser. Here is a scenario that may help. Combos, Fishing Tools & That 2nd paper carb filter is best- filters better!! The pull-off is connected by a linkage rod. JavaScript is disabled. 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. Jan 19, 2011. PFDs, Roof Racks, Carriers, Category, View Some black smoke out of the exhaust. 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. They are actually about as simple as a stone axe. Another possibility, and it is real. Boat, Sell A Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! Research the jetting. Boat, Boat Buyers Blowing through the check valve side did open and allow air through. However, when you start making modifications such a hot roller camshaft, aftermarket induction and heads, and a host of other performance elements the Quadrajet struggles to keep up. Cushions, Lexington Most modern Hangers are identified by letter stamping, offered in increments from B to V. 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. Lights, Boat Trailer It would not be a permanent fix by any means, but until all the parts for the choke are located I figured this could serve the same purpose. This design is not unique to the Quadrajet. Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. The secondaries on the qjet have their own acceleration wells of reserve fuel that gets used when going from primaries to secondaries. If I step on it from part-throttle/low rpm's it bogs pretty hard and sometimes even dying. Accessories, PWC Parts & This is known as electronic mixture control. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. Accessories, Big Jon Because the fuel bowl is central it keeps fuel more stable in a variety of driving conditions, with less chance of fuel starvation. And this has been proven in drag racing for decades. 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. Starters, Marine Solar Power Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). Good for the interstate cruise. All employ air valve transition into the secondaries. Then, passages can be capped off with high-temp epoxy or lead. Acessories, Fishing Outriggers & Smoke Details: SBC 350 - Stock high mileage motor Quadrajet - APT screw turned out 1.5 turns from bottom w/ 67 jets. Boarding, Paddles & Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! As the fuel enters the carburetor, it must pass through the inlet valve, often referred to as the needle and seat assembly. Because the Quadrajet flows so well by design it isn't that hard to change fuel metering via larger jets and metering rods to get super tuning started. Marine Battery Chargers, Shop Axles, Boat Trailer Tie To prepare a Q-Jet for competition or street performance, there are several areas that require special attention. Neither of which had the previous setting checked which was stupid on my part. 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. A Quadrajet rebuild is actually quite simple. Fuel metering became electronically controlled in 1980. That check valve being coroded up badly was the main culprit!1 The paper filter -likely was catching the crap from that corosion!! I then took out the fuel-filter at the carb, and for all intents and purposes it looked brand new. Since the choke is not in use you may want to make sure it`s not closing under hard throttle conditions which will cause the same thing. did you pull the manifold? A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Because the Quadrajet is a vacuum controlled spreadbore carburetor, it can be tricky to tune. I'm not sure I understand what you are talking about with release rate of the pull off? Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more! 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. Did you know Ford ran the Quadrajet on its 1970-'71 429ci big-blocks. LOL. Swap meets are another excellent place to find a good core. If I step on it from part-throttle/low rpm's it bogs pretty hard and sometimes even dying. Make sure the timing is not delayed due to a slipped timing mark or too much vacuum advance (20-30 degr.). Detectors, Binoculars & Breakers, Power Packs & Jump Vacuum leaks can pop up elsewhere, too, between carburetor body contact surfaces and vacuum ports. Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Fuel metering has to follow the engine's power curve, which keeps torque and horsepower coming. Non computer controlled (1986). Lighting, Marine Teak Boat Gel Coat - Spectrum Color, Pumps and 05. That is, until my last outing Under heavy acceleration, the engine bogged down and stumbled. This added to my concern for the pick up tube. GPS Chartplotter and Fish Finder Combo, Find Telescopes, Covers and Take it apart and lightly sand-clean it. Accessories, Marine DC Power Plugs 1,364. Convenient when it's time to pin the butterflies. Could this work just as well in place of the choke rod? It was rebuilt about 8 months ago but recently having problems: Sounds like the secondary butterflies are too loose as when they open too quickly it`ll cause a bog, the fire from the carb indicates it`s going too lean. Financing, Iboats 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. http://forums.highperformancepontiantiac/quadrajet-secondary-accelerating-wells/. The objective is cleaner emissions and finite power tuning and fuel efficiency. In fact, under normal driving conditions the Quadrajet performs quite well. Tackle Boxes, Fishing Bait & It may not display this or other websites correctly. Thanks folks!!! And fuel pump pressure. Covers, Boat Shrink Wrap Too many of us give up because this carburetor requires time, knowledge and patience. 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. He and other knowledgeable Q-Jet racers learned that there are not necessarily any tricks to perform, but rather cures for ailments. Terms of Service. The Bog simply means the engine is not receiving enough fuel when you go to wide open throttle. 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. The one on before that lord only knows how long it was in there. Sounds like a possible float issue to me. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Ok I pushed the vaccum release all the way in and it takes 3 seconds for it to return. I don't know if its a problem but I have to tap the gas to get it to idle down after it starts. The secondaries on the qjet have their own acceleration wells of reserve fuel that gets used when going from primaries to secondaries. Meters, Marine Electrical Panels The trick is finding a good core you can build from. A forum community dedicated to custom off-road vehicle owners and enthusiasts. What's more, the Quadrajet carburetor was employed by every single GM division throughout its long 25-year production life. If you dont want it give it to me. Dollies, SportsStuff Great Big VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. Well said Tech. Pumps, Marine Pump Replacement I rebuilt the 4-bbl Quadrajet in 2013 and haven't had any issues since. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. http://www.73-87.com/7387garage/drivetrain/myqjet.htm. That's the best all around deal. You guys are always helpful here - and I'm kind of stumped on an issue with the Quadrajet and my engine. Pumps, Livewell Aerator Pumps I did some looking on this site and others and i've done a lot of youtube watching on these carbs. 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. 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Precisely control the air/fuel mixture control the air/fuel mixture advance disconnected.HEI distributor Elevation is 9,000ft secondary air valve until!