I'm running a bone stock '73 455 in an Electra. The carb is stock and looks like it was never touched in it's life. The car only has 80k miles so it's not that much of a suprice. I'll list the issues in order to make it easier to follow. 1) Cold starts just don't happen. It takes about 30 tries to get the car to actually start and when it does the idle is super low and the car sits right on the verge of stalling. If I hit the gas to raise the rpm the car instantly dies. 2) The car has a deffinite stumble at idle. It's consistant but not clockwork enough to suggest a bad plug or wire. 3) Just off idle the car stumbles more and tries to stall 4) Once the car is up to temp the idle is extremely high 5) When warm and coming from a dead stop hitting the gas either makes the car roar to life or stumble like it's about to explode and then stall 6) Hitting the gas when it's warm stalling has absolutetly no effect. It's as if the throttle isn't even attatched 7) When I shut off the car when warm (high idle) the car diesels for a second or 2 and then a small cloud of smoke comes from the throat of the carb. This doesn't happen when it stalls. A few side notes: Car starts great when warm but has the high idle in park and goes instantly into the low idle stumble when shifted into gear When the car is cold and off the front butterfly only opens about 1/4" at full throttle. Nothing else opens. All the linkages move freely and the front/rear butterflies can be opened by hand with light/moderate pressure. When the car is warm and off the front butterflies stay almost completely open (almost fully vertical). All the linkages move freely and the front butterfly can be closed with light pressure but snaps back open when pressure is removed, the rear butterflies open freely under moderate pressure. I'm already pricing out an edelbrock swap since it's easier to get a good "grocery getter" tune, but I'm not going to give up on this carb if it can be fixed with a screwdriver in the driveway.
Send the Q jet to a pro rebuilder. It is a very good carb in many ways more advanced the the E brock AFB design. However after 80K miles it will need a total rebuild to operate as it once did.
Before we condemn the carb, I would suspect the car is in need of a good tune. It sounds like the car is severely out of adjustment. I would also suspect a vacuum leak. What condition are the points in? Cap and rotor? Wires? How many miles on the plugs? What do they look like? Have you had a vacuum gauge, dwell meter or a timing light on it recently? Have you adjusted the choke or mixture screws at all?
Car had a full tune-up just before I bought it, so about 300 miles ago. Everything on that end looks fine and doesn't seem to be an issue. I'm going through every hose over the next week with a vaccuum pump to ensure that they are all in good shape and hold vaccuum. Timing light is on backorder so it's waiting for another week or 2. I'm thinking there may be a small vaccuum leak somewhere, as well as a fualty choke, and leaky wells.
Edelbrock doesn't make a replacment carburetor for the factory divorced choke Quadrajet. They make AFB and AVS "clones", which are complete piles of junk. IMHO They fit the bill for moving most vehicles point A to point B, but they require an adapter plate, cutting the factory fuel line and routing it to the left rear of the carb, cobbling with linkage, running a wire for the choke, etc, etc. We woln't touch those carburetors here, and the best sound they make is when the "tink" off the dumpster behind the shop! Seriously, the carburetor needs a "tune-up" just like the distributor, and it's manditory to upgrade it with modern parts for this new fuel.......Cliff
I've never had a problem with e-brocks and ran them on everything from a Pontiac 389 to an Olds 350 along with the standard old Chevy small block. Since this is a car the size of a building and it's never going to be raced I don't really need to worry about getting the best 6,500+ rpm performance from it. Just slap it on and get where I need to go is all I'm looking for. On a side note though, what are your going rates for doing a nice "full" rebuild on one of these old carbs? Make it like new and hopefully I won't need to touch it again for another 80k miles. If the cost is the same then it's worth a look at going in that direction. I've looked at enough manuals to know I can't do a rebuild myself. Arthritis doesn't like fine detail work
Off-idle stumbles are often an indication of a too-lean condition, my Q-Jet had the same issue for a while. Even though I had new 73 jets and 41 rods in a custom rebuilt 4MV (cost over $800), the transition from idle to main was never smooth, and the idle was always choppy with a lean miss. No amount of adjusting the idle screws could fix it. Putting in 39 rods fixed the stumble. I later rebuilt my own factory-correct 4MV, and ditched the expensive Rembrandt for parts. Even so, there's a chance your power piston could be stuck, or the rods could be bent...90% of the operation of the Q-Jet is through the primary metering system. Any problems with this system will screw up everything else. When engine cold and off, one pump of the accelerator should snap your choke blade (butterfly) completely closed & kick the fast idle cam into its top notch. The choke spring should be holding the butterfly shut for cold starts. If it's still 1/4" open when the engine is cold & off, your choke is not adjusted correctly. Once the engine is started & running, the vacuum break diaphragm will pull the secondary rod down, and open your butterfly about 1/4", depending on your exact carb model. As the engine warms up, the choke should eventually allow the butterfly to open completely, and your idle speed will eventually reduce to the warm idle of about 700-800 RPM.
I have a q jet carb sitting here in a box that came off a 73 electra with a 455. My dad rebuilt the carb about 3 years ago and the car ran fine. couple of months later the guy changed to an edelbrock. I really have no use for this carb if you are interested in purchasing it. $75 shipped
I'll keep this in mind. If I decide to do any sort of "home build" then I'll need a backup for when I screw things up. The last time I took apart a q-jet I ended up with a box of parts and screws and had no clue how to put it back together. That's how I know that these carbs are far beyond my simple mind ou:
Where is the carb number stamped on the carb? I'd like to write it down for reference but can't remember off hand where the number is located.
Dude Cliff rebuilds some of the best carbs... and not a backyard/ shade tree rebuild. search the forum a bit look for the name cliff. :3gears:
I know who he is. Just know that I can't afford his prices based on what little info I've heard from people. I've never gotten a full price quote directly so it's all hear say at the moment.
"Putting in 39 rods fixed the stumble. I later rebuilt my own factory-correct 4MV, and ditched the expensive Rembrandt for parts." Most of the early Buick units will have this feature. We install an external adjustment so the user can dial in the part throttle A/F ratio without taking the carb apart and changin the metering rods.....Cliff
The part number is on the drivers side of the main body stamped vertically. It would start with 7043 if original. Maybe 7043240
