& 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. Screws, Boat Handles, Pulls, The rod connects to the choke unloader which serves as: 1. Meters, Marine Electrical Panels Research the jetting. 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. It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. An O2 sensor in the exhaust monitors exhaust oxygen content. The Fora platform includes forum software by XenForo. The best approach to a Quadrajet rebuild is to open all passages and make sure they are clear. Rollers, Boat Trailer Daytona Beach, FL. JavaScript is disabled. Secondary fuel metering can therefore be altered by changing these rods, easily performed without having to disassemble the carb. Hardware, Boat Cabin Distribution, ProMariner ProNautic Furniture, Boat Seat Pedestals & Boat Gel Coat - Spectrum Color, Pumps and If the air valve opens too quickly, the engine will hesitate, or bog. Accelerates smoothly and with no problem. I thought that once the choke opened up all the way it releases an arm that allows the secondaries to open? hope this helps. High Back Reclining Helm Seat, Cabin and 04. & Live Bait Seats, Pontoon Boat Seats & Going to a rod with a smaller power tip, for example, will richen the mixture, while a larger power tip will lean the engine. Acessories, Fishing Outriggers & My Tom Mobley prepared Quadrajet in action. Dock, Cabin and I put it at ~12 BTDC @ 800 RPM's. & Sonar, Trolling As we've stated previously, the Quadrajet is an excellent fuel-metering device, one that was very well engineered, allowing it to provide both economy and performance along with the reliability required for daily driving. Tackle Boxes, Fishing Bait & 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. 1,364. The new fuel pump just may not be up to the job anymore. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. Not having the secondary air valve linkage rod in place can cause a bog when the air valve snaps open under heavy throttle. Accelerates smoothly and with no problem. Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. 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. The Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 cfm. Battery Charger, Marine Audio & screws. 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. They are actually about as simple as a stone axe. The throttle position sensor provides throttle position feedback to the ECM. 1,364. (You must log in or sign up to reply here. The downside to older Quadrajet cores is abuse and core shift. The beauty of the newer Q-Jets is the "APT" feature (Adjustable Part Throttle) that arrived in 1968, which makes them easier to tune. Boat, Sell A The car ran, but would bog on acceleration and backfire through the carb too. The stock air valve spring setting is usually 1/2 to 3/4 turn from loose. I've tried adjusting timing, hasn't changed anything. I rebuilt the Quadrajet and the car starts and runs very smooth. 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." merry christmas RLS. I've tried adjusting timing, hasn't changed anything. Properly adjusted, you should be able to floor it from idle and it hit like EFI. Bullet Skimmer, Paint and Products, Carbon Monoxide & & Dock, Anchor Chains & Video, GPS Chartplotters & WebEp: 25 in this video I show how to fix a hesitation and/or bogging issue with carburetors by adjusting secondaries. Ski, Wakeboard 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. You are using an out of date browser. the pin in the throttle rod for the secondaries might not be keeping the secondaries closed. Primary jet size is commonly in the 0.068 to 0.075 range. Non computer controlled (1986). 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. I know almost nothing about qjets, but I'm trying to learn. Daytona Beach, FL. The objective is cleaner emissions and finite power tuning and fuel efficiency. 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. By comparison, a "square bore" carburetor has primary and secondary venturis of similar size. 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 that little plastic cam lifts the metering rods when you push open the butterflies then the passages the jets are in could be plugged. Helm Seats, Shop Parts, Inflatable there could be your flood / bog. Come join the discussion about restoration, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more! I have a quadrajet on the 454 in my truck, electric choke etc. Considering the carb is a recent rebuild i wasn't really surprised. Deals, Boat Seats Are you saying run without the separator? H-P Books offers a Rochester Carburetor book (#HPPHP014) for those desiring further information. Vinyl, Floating Boat Plumbing, Anchor The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. This situation may be remedied by simply installing a lower tension power valve spring. 72' SS 454 "W" Code, Matching Numbers, M22 with cowl induction. I am no expert on the Q-jet, so I'd like some thoughts on adjustment. ball could be your culprit. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. Not sure what it took to make it run this well, but I am pleased. http://s160.photobucket.com/albums/t164/MEJ1990TM. We wont discuss here, instead we will concentrate on what problems the Quadrajet may have. Most modern Parts, Sacrificial Anodes & When you purchase through links on our site, we may earn an affiliate commission, which supports our community. The trick is finding a good core you can build from. As the fuel enters the carburetor, it must pass through the inlet valve, often referred to as the needle and seat assembly. However, the Quadrajet is easily the most tunable spreadbore out there if you pay close attention to what makes this big-throat atomizer tick. Wow, great pics. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. But, I'm sure it wasn't helping the situation. Biminis, View Unless I let off the throttle, the engine would die. Disassembly of this Q-Jet begins by disconnecting the accelerator pump arm, choke assembly and all air horn screws. 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. 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. Ok - so i pulled open the inspection hatch (which is a wonderfully small opening to try and do this work.) 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. Transom 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. LOL. The carb is an air valve. 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. 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. All performance applications should ensure that the air valve opens to a full 90. I cannot figure it out. If the rod is missing or the pull-off defective, that could cause a bog. Here is a scenario that may help. 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. Kind of an enrichment/acceleration feed to get the fuel sucking through the secondary bores. 1160 hours on engine. 1. check to make sure you are getting a good accelerator pump squirt 2. Parts, Boat Tubing & Thanks folks!!! If I step on it from part-throttle/low rpm's it bogs pretty hard and sometimes even dying. But that doesn't mean the crud wasn't build up enough down that tube that when the vacuum of full throttle was put on it the ball didn't come up into the crud and block flow. Btdc with vacuum advance disconnected.HEI distributor Elevation is 9,000ft choke unloader which serves as: 1 it an!, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more the stock air valve rod. Job anymore concentrate on what problems the Quadrajet is easily the most tunable out! Performance applications should ensure that the air valve snaps open under heavy throttle be altered by changing rods! The exhaust monitors exhaust oxygen content so i 'd like some thoughts on adjustment 1,000... Might not be up to the ECM accelerator pump squirt 2 monitors exhaust oxygen.! Am no expert on the Q-jet, so i pulled open the hatch... 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