Rochester Quadrajet Carburetor
Its last application was on the Oldsmobile V8 engine, which was last used in the Cadillac Brougham and full size station wagons made by Chevrolet, Pontiac, Oldsmobile, and Buick. Not widely known, the Q-jet was used briefly by Ford on the Cobra Jet and was also used by Chrysler Mopar on their truck engines in the ’80s. The Quadrajet has been described as one of the best carburetors made for passenger vehicles, offering the best compromise of fuel economy, performance, driveability, and emissions control. By comparison, a “squarebore” carburetor may have primary and secondary venturis of similar if not exactly the same size and the center to center spacing of the primaries and secondaries are the same, thus the name “squarebore”. Most Quadrajets made prior to were capable of cubic feet per minute CFM maximum air flow measured at a 1. The increase in airflow was due to a larger primary venturi. In Pontiac had designed a special Q-jet that had the most flow of any production Q-jet, but because the modification decreased the vacuum signal on the primary side too much it was discontinued, so it was a “one year wonder” that fetches outrageous prices from restorers today. Many more cfm Q-jets were installed from up.
Before you start work, replace any cracked or missing vacuum hoses, and check vacuum hose routing against your service manual diagrams or, in most cars, a color sticker under the hood somewhere. Make sure you get the right grade of vacuum hose; anything carrying gasoline or emissions fumes require a special material. When in doubt, get the pricier but safer gasoline-safe hoses.
Vacuum hose, gauges, and Ts are sold by most auto parts stores. Vacuum gauges are usually large dials with a narrow rubber hose or metal hose grip leading out; most come with various plastic tips and fittings.
Mar 16, · I always see a lot of questions about what various vacuum ports do on a Quadrajet. Here’s a general guide that will point you in the right direction.
Under the hood, it had a small block V8 engine with a Rochester QuadraJet carburetor. We were too focused on doing body work to worry about the engine at first. In the summer of , I decided to take a look at the rebuilding the carburetor. I found a couple of companies that offered rebuild services by mail. Having ruled that option out, I looked at the cost of buying a Holley or other brand of carburetor. There was only one option left:
How Carburetors Work – Carbin’ It Easy
How to Install a Rochester Carburetor on an Engine by Chris Stevenson Rochester garnered fame with the Quadra-Jet carburetor, but their two-barrel models were equally praised. The four-barrel design incorporated two huge, secondary throttle bores that allowed an extra-large volume of fuel and air to enter the intake manifold. They were very popular decades ago and can still be found on classic and muscle cars today. Basic in design, they lend themselves well to rebuilding and high-performance modifications.
You can swap them out with different makes and designs with the use of adaptor plates. Alternatively, you can simply bolt them back onto their original intake mounts.
Apr 27, · Curing Quadrajet Carb Woes–Here Are Some Interesting 21st Century Fixes For Your 20th Century Rochester Carburetor – Super Chevy Magazine.
The rebuild never seems to last and some of the areas like leaking around linkage and dry gaskets are often not fixable. They are too complicated, too hard to adjust, and in a difficult place to work on. I have a new engine, is the old carb still correct for the heavy breather? With a closed loop control, this should be adjusted automatically. I think basically, I hate carburetors.
These are the parts to be added. Need to get under the wheel wells and do some work so it is suggested to raise the front of the coach. I feel safer with it up on blocks and this was enough height. This picture shows that it is necessary to put a block or stand under the rear of the GMC when ever you are under the rear.
Curing Quadrajet Carb Woes – Tech
Many people that aren’t concerned with originality quickly give up on a GM Rochester Quadrajet carburetor and replace it with an aftermarket piece. The oft-maligned Quadrajet has been the victim of much verbal abuse, with such nicknames as “Quadrajunk” and “Quadrabog”. Truth be known, though a little complicated, they are one of the most precisely metered and best designed carburetors ever made.
Millions were installed on many different GM engines in the 60’s, 70’s, and 80’s, as well as some non-GM vehicles. The small primary bores gave good fuel economy, throttle response, and emissions control, while the huge secondaries when called upon would boost air flow to CFM for most versions and CFM for a few others.
Carburetor Fuel Fittings – Carburetor Parts & Kits for Rochester, Carter, Holley, Edelbrock, Ford Motorcraft QJet, 4G, 2G, Mercarb Marine, AFB, AVS Thermo-Quad Carburetors.
Originally Posted by Kath View Post So I got the quadrajet remanudactured carburetor for my 69 automatic Vette but I thought it would have an electric choke. It has a manual choke. Oops – forgot to read ALL the details. What are my options now? Can I buy and fit an electric choke easily? My fearless mechanic son-in-law tells me that the original would have been electric because I don’t have a choke knob inside to pull. So now I have to put a hole in the dash and hook up a cable and a knob.
I could also just send the carb back and buy the Holley one with an electric choke but you guys already told me that the rochester was better. Any advice would be greatly appreciated before I start putting bullet holes in the dam thing. Kath I would set it up with a mechanical choke, with the manifold mounted coil that opens the choke as the engine warms up.
I would expect that’s what came on it originally.
Vacuum ports on a Quadrajet
In a squarebore, the bores are closer to the same size, though, in some squarebore carbs, like cfm Holleys, the primaries may be noticeably smaller than the secondaries. However, even then the bores share the same centerline. Many aftermarket intakes, such as mine, and the Edelbrock Performer and RPM, etc, are “dual pattern” intakes the area where the carb bolts on looks like a butterfly. Either a squarebore OR spreadbore can be physically be mounted on them with no adaptors.
Sep 13, · [ QUOTE ] Guys, I’ve recently gotten the fever again – after having 3 kids – to finish throwing the 51 back together. The carb setup I have for it is .
Nearly 22 years ago now. Today, it has 95, miles. A large percentage of that 58, mile difference has been off-road in the Pacific Northwest. The rest has been getting to and from the trail-head to leave the pavement. I traced this rig’s history and spoke to it’s original owner not long after buying it. He had purchased it as a dealer “demo” with 4, miles on the odometer. He used and abused it hauling a 55gallon drum, hunting dog cages, and pulling a 12′ trailer before the Repo-man mercifully rescued her from him, returning her to a Mike Salta dealership in Portland.
That dealership was closing, and she was wholesaled to Beaverton Datsun, where she and I first we met. It’s been a love-hate relationship. Water leaks into the cab it’s been known to rain a bit in the PNW , the occasional ill-timed breakdown, and she even has a spot or two of skin cancer these days. But, just about the time I’m finally convinced it’s time to say goodbye, some stranger will ring the doorbell, apologize for interrupting dinner, and darn-near beg me to sell her to him.
That’s when I say again that I’ll probably be buried in her instead of a casket.
Carbureted Nitrous Systems » Q-Jet (Spreadbore Flange)
Design[ edit ] The Quadrajet is a “spread bore” carburetor; the primary venturis are much smaller than the secondary venturis. By comparison, a “square bore” carburetor has primary and secondary venturis of similar size. A less-common version uses a linkage driven off the primary throttle shaft to mechanically move the power piston.
Find great deals on eBay for quadrajet carburetor. Shop with confidence.
We are the third owners and have had this wonderful GMC for 17 years. It has always been garaged and is in excellent condition. Solid walnut cabinets, roof air conditioning and 6kw Onan generator. Cared for as a family member. Always garaged and continuously maintained and upgraded, it is in excellent condition. Solid walnut cabinets, 2 roof air conditioners and 6kw Onan generator. Engine and transmission are strong trans overhauled at 62, The coach has had many mechanical upgrades and comes with a variety of spare parts.
It needs cosmetic interior and exterior work but has great potential. Some of the upgrades include: Onan generator has not been used so I cannot attest to it’s condition, the air suspension system is in need of repair or upgrade, newer engine battery, coach battery needs to be replaced. For additional information and upgrades. Runs great, drives great and such a cool unit. Roof AC, Onan Generator, new batteries.
How do I hook up a heat choke on a quadrajet?
November 23, , It might be best if you could post a pic of your Q-jet so I can be sure we are talking about the same thing. But for a mid ‘s to early ‘s non electronic Q-jets, the distributor vacuum advance goes to the small vacuum port on the front lower driver side of the main body to the right of the filter housing if you are looking at the front of the carb.
This will be your “high signal” timed vacuum there is also a port just above the fuel filter housing that should be the “low signal” timed vacuum port for things such as EGR. Confirm this by putting a vacuum gauge on each of these ports and opening the throttle slightly. One will have a signficantly higher vacuum reading.
Apr 28, · How It Began. The Quadrajet was released in , and since then, saw a long and fruitful life installed on GM cars until EFI took over. The Quadrajet was actually the successor to the previously-built Rochester 4GC carburetor that was manufactured from to
Chelmsford, England, UK Arick, Don’t connect the vent line from the tank to that large port at the front of the qjet. That qjet port is for PCV, is full on vaccuum and way too much pull on the vent to the tank. If you are getting rid of the canister, do as Damon suggests and ensure the end of the vent line can breath where no dirt can enter it and any fumes coming from it can’t be ignited. I personally don’t see what the fuss is about removing the canister – it recovers petrol vapours and reburns them without any adverse affect on performance which is not just ecologically sound it also gets the most out of your fuel.
If you do keep the canister, the vent line from the tank connects to the center port of the canister, and any escaping vapours are trapped in charcoal situated below it. There are two vaccuum lines that connect to the left hand valve on the canister – a full vaccuum from the qjet pcv port to the underside of the valve, and a ported vaccum to the top side typically via the egr thermal switch.
The full vaccuum pulls on nothing, unless the ported vaccuum signal is strong enough to open the valve. When the valve opens, the full vaccuum pulls vapours out of the charcoal together with fresh air from the underside of the canister, and into the engine via the pcv port on the front of the qjet. The jets and needles in your qjet are calibrated to deal with this slight leaning at high ported vaccuum signal.
Quadrajet Vacuum Line Diagram
It is an opportunity for us to reflect on the language and ideas that represented each year. So, take a stroll down memory lane to remember all of our past Word of the Year selections. Change It wasn’t trendy , funny, nor was it coined on Twitter , but we thought change told a real story about how our users defined Unlike in , change was no longer a campaign slogan. But, the term still held a lot of weight. Here’s an excerpt from our Word of the Year announcement in
Rochester Carbs Quadrajet parts page many hard to find parts Jets chokes pulloffs rods fuel fittings.
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Fc Remanufactured Products known as Foreign Carburetors since Our carburetors can be purchased nationwide in over 20, different locations; AutoZone, Car Quest, O’Reilly, NAPA and over 5, other independent auto parts stores from coast to coast. By combining the latest refinishing technology and new parts plus years of experience our carburetors look better than new. They are “National New. All other components are cleaned, tested or rebuilt to meet O. The base plates are rebushed to remove excess wear from around the throttle shaft to stop certain vacuum leaks.
All bolts and linkage parts are zinc plated. As well as casings are tumbled to chrome like finish.
For decades the Edelbrock company has made aluminum heads, intake manifolds, carburetors, and other accessories for the high-performance market. It offered both replacement and high- performance Quadrajet carburetors for many years. The replacement units were limited to several basic styles, all with side fuel-inlet locations and both electric and divorced chokes.
It was the first and only true high- performance Quadrajet ever offered in large production by an aftermarket manufacturing facility.
Oct 10, · The Quadrajet was never developed to be a high-performance carburetor to begin with though GM installed this carburetor in dozens of high-performance applications.
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