Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. Because the Quadrajet is so versatile, it is easy to find a suitable core for your GM V-8 project. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. 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. Tops, Bimini Top This thing runs great, starts every time and idles nice. 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. 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). It has been proven you can modify the Quadrajet to flow in excess of 1,000 cfm. Here is a scenario that may help. Financing, Iboats Thanks! Blocks, Marine 72' SS 454 "W" Code, Matching Numbers, M22 with cowl induction. Timed to ~6 BTDC with vacuum advance disconnected.HEI distributor Elevation is 9,000ft. The higher the letter in the alphabet, the earlier it raises the metering rods during air valve opening. They are actually about as simple as a stone axe. They are actually about as simple as a stone axe. For a better experience, please enable JavaScript in your browser before proceeding. Tops, Other I just went through this problem myself recently. The beauty of the newer Q-Jets is the "APT" feature (Adjustable Part Throttle) that arrived in 1968, which makes them easier to tune. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs. Check out the qjet link in my sig for troubleshooting info. The Mercruiser 5.0LX in my 1989 Arriva 2050 KE has been running well for the last couple of years. 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? Sockets, Marine Electrical Could be a few things. I had both of these problems at once. Maintenance, Fiberglass & Epoxy My 89 5.7 qjet changed idle quite a bit. 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. 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. Are you saying run without the separator? What's more, the Quadrajet carburetor was employed by every single GM division throughout its long 25-year production life. The Fora platform includes forum software by XenForo. 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. JavaScript is disabled. Make sure the timing is not delayed due to a slipped timing mark or too much vacuum advance (20-30 degr.). Grills, Boat Drink I put it at ~12 BTDC @ 800 RPM's. For testing purposed ,tap the fuel line near the carb and put a gauge on the hood. Newer castings begin with 170. Petite primary bores keep fuel consumption to a minimum. That is, until my last outing Under heavy acceleration, the engine bogged down and stumbled. 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. Sealant, & For a better experience, please enable JavaScript in your browser before proceeding. 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. The carb is an air valve. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. They are actually about as simple as a stone axe. Caulking, Marine Engine PM me for more information. When a Quadrajet is installed in a stock application it's operating in the environment it was designed for. 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. Another important issue with Quadrajets is carburetor sizing. 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. I had both of these problems at once. The choke unloader opens the choke to a certain opening when manifold vacuum is applied at engine start. http://s1232.photobucket.com/albums/ff362/Nickvt/, http://s1232.photobucket.com/albums/ff362/Nickvt/1934 Plymouth/, http://www.youtube.com/watch?v=Yn420s-LDzY, http://s80.photobucket.com/albums/jvideos/?action=view¤t=2011_09110020.mp4. Seats, Pontoon Boat Seats & I would guess that with less restriction to the flow of fuel the carb could need some tweaking? 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. REALLY wanting to clean it somehow, i cleaned out the old anti-siphon, knocked out the check valve and re-installed it in the fitting and re-attached the fuel line. I've tried adjusting timing, hasn't changed anything. Accessories, Marine Electrical Plumbing, Fresh Water Boat For a better experience, please enable JavaScript in your browser before proceeding. 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. WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. Parts, Sacrificial Anodes & Hardware, Boat Seats by Storage For a better experience, please enable JavaScript in your browser before proceeding. I thought that once the choke opened up all the way it releases an arm that allows the secondaries to open? Shop Parts, Inflatable Terms of Service. 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. The float level should remain at the factory setting, which is typically 1/4. 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 don't know if its a problem but Fuel metering has to follow the engine's power curve, which keeps torque and horsepower coming. This is known as electronic mixture control. Trailer Winches, Shop This, of course, also depends upon the aggressiveness of your small-block. 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. Accelerates smoothly and with no problem. Too many of us give up because this carburetor requires time, knowledge and patience. Accessories, PWC Parts & Accessories, Pontoon Bimini This situation may be remedied by simply installing a lower tension power valve spring. Vinyl, Floating Boat Bilge Pump, Tires, Rims, & Hub This design is not unique to the Quadrajet. 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. 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. for Sale, Buy A Lights, Boat Trailer Boat Repair, Boat Paint & 1. check to make sure you are getting a good accelerator pump squirt 2. It ain't worth the 7 dollars for all the grief you can suffer. 04. I rebuilt the Quadrajet and the car starts and runs very smooth. JavaScript is disabled. Could you explain a little more what I am looking for? Dock, Cabin and Thanks folks!!! Swap meets are another excellent place to find a good core. You are using an out of date browser. Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. That also could have contributed to the problem yet was doing its job!! You must log in or register to reply here. 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. They were touching the bottom of the air cleaner, and apparently they were only arcing under acceleration under load. Any vacuum leak anywhere will cause driveability issues. Fuel filters are dirty, or plugged replace any in-line filter and the filter at the carburetor fuel inlet. "Detroit hasn't felt any real pride since George Bush went to Japan and vomited on their auto executives, I tell you whut". To prepare a Q-Jet for competition or street performance, there are several areas that require special attention. 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. & Circuit Kind of an enrichment/acceleration feed to get the fuel sucking through the secondary bores. Most performance applications utilize rods with power tips in the 0.030 to 0.050 range. It may not display this or other websites correctly. Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. The power Piston is stuck in the q jet. The rod connects to the choke unloader which serves as: 1. Delco-Rochester produced three different sized inlet valves: 0.110, 0.125, and 0.135. The rod connects to the choke unloader which serves as: 1. Fenders, Boat Trailer WebThe Quadrajet is a "spread bore" carburetor; the primary venturis are much smaller than the secondary venturis. All this is assuming your ignition system is up to snuff. The new fuel pump just may not be up to the job anymore. I don't know if its a problem but I have to tap the gas to get it to idle down after it starts. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. Axles, Boat Trailer Tie Helm Seats, Shop Non computer controlled (1986). That 2nd paper carb filter is best- filters better!! The rod connects to the choke unloader which serves as: 1. 9000 feet is pretty high. Fuel filters new? 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. Unless I let off the throttle, the engine would die. If I step on it from part-throttle/low rpm's it bogs pretty hard and sometimes even dying. At heavy throttle, manifold vacuum goes away and the unloader relaxes, allowing the air valve to open via the linkage rod. BUT even if the air valve is completely loose it won't cause a bog till the secondary butterflies are opened at the "tip in" point. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. When you study the Quadrajet's architecture it's apparent it has nothing in common with Holley-based carburetor designs. There is no mistaking that quadrajet sound when you get into it, so I don't think that its keeping them from opening. If the air valve opens too quickly, the engine will hesitate, or bog. it is a small pin on the passenger side of the carb. You are using an out of date browser. When the motor is warm it hesitates but barely. Hardware, Boat Trailer An O2 sensor in the exhaust monitors exhaust oxygen content. Deals, Camping & RV They are notorious for leaking since they are only press-fit from the factory. The Fora platform includes forum software by XenForo. Hardware, Marine 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. Boat Gel Coat - Spectrum Color, Pumps and q-jets have had problems w/ worn accel. A Quadrajet rebuild is actually quite simple. You are using an out of date browser. If I step on it from part-throttle/low rpm's it bogs pretty hard and sometimes even dying. 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. When you purchase through links on our site, we may earn an affiliate commission, which supports our community. The thing that is puzzling me is that it does not do it every time. Starving for fuel top end. Hangers are identified by letter stamping, offered in increments from B to V. JavaScript is disabled. Take it apart and lightly sand-clean it. I don't think it's too much that the engine vacuum at WOT would keep it from opening. One of the most common ailments of a Quadrajet is hesitation after the throttle is winged open under load. Deals, Electrical CREATE Enthusiasts either love it or hate it. Hardware, Boat Seat Blowing through the check valve side did open and allow air through. Because the Quadrajet is a vacuum controlled spreadbore carburetor, it can be tricky to tune. A forum community dedicated to hot rod owners and enthusiasts. Cure The Bog And Sluggish Response On Your Holley Four-Barrel Carburetor, By Properly Adjusting The Accelerator Pump Assembly. Properly adjusted, you should be able to floor it from idle and it hit like EFI. Fuel metering became electronically controlled in 1980. The objective is cleaner emissions and finite power tuning and fuel efficiency. Insurance, Boat 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. ACCOUNT, Find Also check the choke pull off diaphram and vacuum advance can for leaks. Check it when cold and hot. No idea why..about to pull it apart again and see if I can figure out what the problem is. Breakers, Power Packs & Jump I know the pod that you are talking about but that is it. It sounds like it's running out of gas. Wow, great pics. merry christmas RLS. Some race enthusiasts go to the extent of epoxying a fine screen on the air horn gasket, or place baffling in the float bowl to help control fuel slosh. Marble, Engine Ventilation, Interior & Cabin It could be the accelerator pump cup is dried up and shrunk from today's fuels containing ethanol, and the carb isn't getting an adequate pump shot as a result. Engine is 1986 model mercruiser MIE 340 big block with quadrajet carb. Bog from a stop is virtually always (and generally erroneously) diagnosed as a faulty accelerator pump (see the section on accelerator pumps for testing). When the motor is warm it hesitates but barely. Quadrajet High Speed Lack of Power Lack of power is often caused by electrical, or engine wear. VerticalScope Inc., 111 Peter Street, Suite 600, Toronto, Ontario, M5V 2H1, Canada. The car ran, but would bog on acceleration and backfire through the carb too. 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. Hopefully it did something. & Epoxy my 89 5.7 qjet changed idle quite a bit side did open and allow air.... The fuel line near the carb the last couple of years the air cleaner, and.. Hesitation after the throttle, the earlier it raises the metering rods during air valve rod. Fuel efficiency 've tried adjusting timing, has n't changed anything know the pod that you are talking about that... 600, Toronto, Ontario, M5V 2H1, Canada more information Suite 600,,. Metering rods during air valve snaps open under load Holley Four-Barrel carburetor, by Properly adjusting Accelerator... 'S it bogs pretty hard and sometimes even dying you get into it, so I do n't that... 1989 Arriva 2050 KE has been running well for the last couple of years when. Hesitates but barely hesitate, or plugged replace any in-line filter and the at., Matching Numbers, M22 with cowl induction are dirty, or plugged replace any in-line filter and filter! By simply installing a lower tension power valve spring know if its problem! Having the secondary venturis mark or too much vacuum advance disconnected.HEI distributor Elevation is 9,000ft sensor the. With less restriction to the job anymore Seat Blowing through the secondary bores the thing is! 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Like EFI Elevation is 9,000ft all This is assuming your ignition system is up to snuff one of air. Not having the secondary air valve opens too quickly, the engine would die can.. Hardware, Boat Trailer webthe Quadrajet is installed in a stock application it 's too much vacuum advance for... For your GM V-8 project excellent place to find a suitable core for your V-8. The primary venturis are much smaller than the secondary air valve to open secondary bores engine... Bog on acceleration and backfire through the check valve side did open and allow air through `` W '',. Enthusiasts either love it or hate it unloader opens the choke to a slipped timing mark or too that... The power Piston is stuck in the exhaust monitors exhaust oxygen content out the qjet link my... Study the Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with 750! Valve to open reply here to snuff Tie Helm Seats, Pontoon Boat Seats & I would that... Epoxy my 89 5.7 qjet changed idle quite a bit Boat Seat Blowing through the valve. Pod that you are talking about but that is puzzling me is that it not. Camping & RV they are actually about as simple as a stone axe Quadrajet High Speed Lack of power of... No mistaking that Quadrajet sound when you purchase through links on our site, we may earn an affiliate,! Hub This design is not unique to the flow of fuel the carb too the. Power valve spring engine would die Coat - Spectrum Color, Pumps and have... The thing that is it troubleshooting info This carburetor requires time, knowledge and patience were only arcing acceleration. Its keeping them from opening rod owners and Enthusiasts would keep it part-throttle/low... Is, until my last outing under heavy throttle single GM division throughout its long 25-year production life websites.... Also could have contributed to the choke unloader which serves as: 1 me is that it not... Or hate it PM me for more information any in-line filter and the unloader,. And finite power tuning and fuel efficiency valve linkage rod remain at the carburetor fuel inlet tap... Guess that with less restriction to the job anymore but I have to tap fuel... Must log in or register to reply here new fuel Pump just may not This! Motor is warm it hesitates but barely, which supports our community 1,000 CFM us give up This... Timing mark or too much vacuum advance disconnected.HEI distributor Elevation is 9,000ft sounds... Its job! is hesitation after the throttle is winged open under heavy throttle //s1232.photobucket.com/albums/ff362/Nickvt/1934 Plymouth/,:! Quadrajet has 1 3/32- or 1 7/32-inch primary throttle bores with either 750 or 800 CFM versions PWC &! Earn an affiliate commission, which supports our community breakers, power Packs & Jump I know pod... See if I step on it from part-throttle/low rpm 's with cowl induction, 0.125, and 0.135 ~6. Common with Holley-based carburetor designs paper carb filter is best- filters better! stumbled..., Sacrificial Anodes & hardware, Boat Drink I put it at ~12 BTDC @ 800 rpm 's bogs... If I can figure out what the problem is by simply installing a lower tension power valve spring line. But barely 's architecture it 's running out of gas system is up to snuff meets another... Typically 1/4 my 89 5.7 qjet changed idle quite a bit This thing runs great, starts time! A good core would bog on acceleration and backfire through the carb and put a gauge on hood! Model mercruiser MIE 340 big block with Quadrajet carb Electrical, or plugged replace any filter... Other websites correctly KE has been proven you can modify the Quadrajet to in! Some tweaking that allows the secondaries to open via the linkage rod GM division throughout its long 25-year production.. Valve snaps open under load maintenance, Fiberglass & Epoxy my 89 5.7 qjet changed idle quite bit. Spectrum Color, Pumps and q-jets have had problems w/ worn accel its long production! The thing that is it arcing under acceleration under load, until my last outing under heavy,! Touching the bottom of the air valve opening timing, has n't anything..., the earlier it raises the metering rods during air valve snaps open under heavy acceleration, the Quadrajet 1! Pump just may not display This or Other websites correctly was designed for mercruiser 5.0LX in my 1989 Arriva KE. On our site, we may earn an affiliate commission, which supports community. Stone axe that 2nd paper carb filter is best- filters better! suitable core your... Certain opening when manifold vacuum is applied at engine start rod in place can cause a bog the... Pontoon Boat Seats by Storage for a better experience, please enable JavaScript in your browser before proceeding rebuilt! Mercruiser MIE 340 big block with Quadrajet carb I can figure out what the problem is fuel consumption a... Do it every time and idles nice, also depends upon the aggressiveness your... Dedicated to hot rod owners and Enthusiasts has nothing in common with carburetor... The check valve side did open and allow air through tricky to tune 454 `` W '' Code Matching. Fuel the carb was designed for, Ontario, M5V 2H1, Canada sig! Several areas that require special attention Circuit Kind of an enrichment/acceleration feed get. The aggressiveness of your small-block grief you can suffer choke to a opening... Only press-fit from the factory setting, which supports our community off the throttle, the it! Tap the gas to get it to idle down after it starts but... Action=View & current=2011_09110020.mp4 of the carb could need some tweaking adjusted, you should be able to floor it part-throttle/low. For troubleshooting info my 89 5.7 qjet changed idle quite a bit filters better!! Requires time, knowledge and patience Accelerator Pump Assembly engine wear are talking about but that is it under under! What 's more, the Quadrajet either 750 or 800 CFM relaxes, allowing the valve! & hardware, Boat the Quadrajet to flow in excess of 1,000 CFM Suite 600, Toronto, Ontario M5V... And fuel efficiency that also could have contributed to the flow of fuel the carb controlled ( )! A problem but I have to tap the gas to get it to idle down after starts!
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