21
Quadrajet Carb Talk and Tips / Re: Off idle lean condition, suggestions?
« Last post by 77cruiser on March 25, 2025, 05:49:59 PM »You need about 10 more degrees. Put the initial up to about 15.
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22
Quadrajet Carb Talk and Tips / Re: Off idle lean condition, suggestions?
« Last post by Cadman-iac on March 25, 2025, 02:49:57 PM »Cliff,
I've got the distributor set up for a maximum of 41 degrees advance, 10° initial, 16° mechanical, and 15° vacuum.
The mechanical is all in at 3000 rpm, and I'm using manifold vacuum to the advance unit. It's an HEI unit.
I just ran a 200-mile round trip to Tucson and back yesterday, and it seemed to be fine except for a slight fuel starvation issue due to the stuff I have in the supply line. I've got a shut-off solenoid and an electric pump about midway between the tank and the mechanical pump. When I noticed the problem, I turned on the electric pump, and that solved it.
I think I'm going to relocate the solenoid to above the mechanical pump, not my preferred location due to it being seen easily, but better than letting it cause a problem. (Down here on the border; it's necessary if I want to keep it in my possession).
I did have a heat issue coming back because I was running the air conditioning, but it never overheated, just increased by about 15-20 degrees. I'm running a 180 stat, and the gages registered the normal temperature for when it had a 195 stat, so I'm attributing it to the extra load and the steady rise in elevation between Tucson and here.
The engine has just over 1350 miles on it now, still using a slight amount of oil, I believe, due to the Moly rings. I pulled a couple of plugs just to check and they looked great, a slight brown coloring in spots, which I believe is normal.
I did notice that while cruising at 75, at times the AFR would run upwards to 16.0, but if I gave it a little throttle it dropped back down into the richer zones. I'm getting used to seeing the gage fluctuate a lot and I'm paying attention to the circumstances at any given time.
Pulling, accelerating, the AFR is always in the 10.5 to 14.0 range, depending on how many toes I've got shoved into the carburetor.
On the distributor specs, is what I've provided enough, or do you need more specific details? If so, please let me know and I'll find out and post it here for you.
Thanks for your help and expertise I really appreciate it.
Rick
I've got the distributor set up for a maximum of 41 degrees advance, 10° initial, 16° mechanical, and 15° vacuum.
The mechanical is all in at 3000 rpm, and I'm using manifold vacuum to the advance unit. It's an HEI unit.
I just ran a 200-mile round trip to Tucson and back yesterday, and it seemed to be fine except for a slight fuel starvation issue due to the stuff I have in the supply line. I've got a shut-off solenoid and an electric pump about midway between the tank and the mechanical pump. When I noticed the problem, I turned on the electric pump, and that solved it.
I think I'm going to relocate the solenoid to above the mechanical pump, not my preferred location due to it being seen easily, but better than letting it cause a problem. (Down here on the border; it's necessary if I want to keep it in my possession).
I did have a heat issue coming back because I was running the air conditioning, but it never overheated, just increased by about 15-20 degrees. I'm running a 180 stat, and the gages registered the normal temperature for when it had a 195 stat, so I'm attributing it to the extra load and the steady rise in elevation between Tucson and here.
The engine has just over 1350 miles on it now, still using a slight amount of oil, I believe, due to the Moly rings. I pulled a couple of plugs just to check and they looked great, a slight brown coloring in spots, which I believe is normal.
I did notice that while cruising at 75, at times the AFR would run upwards to 16.0, but if I gave it a little throttle it dropped back down into the richer zones. I'm getting used to seeing the gage fluctuate a lot and I'm paying attention to the circumstances at any given time.
Pulling, accelerating, the AFR is always in the 10.5 to 14.0 range, depending on how many toes I've got shoved into the carburetor.
On the distributor specs, is what I've provided enough, or do you need more specific details? If so, please let me know and I'll find out and post it here for you.
Thanks for your help and expertise I really appreciate it.
Rick
23
Quadrajet Carb Talk and Tips / Re: Carburetor build
« Last post by Cadman-iac on March 25, 2025, 02:17:58 PM » Paul,
I realized I gave you the wrong location for the engine code on your big block. It's on the right side of the block just above the water pump mounting at the base of the head, there's a small lip or ledge it's stamped into, the same as the small block. I apologize for that.
The code you're looking for should be a 3 letter sequence, something like TRU, TRS, or similar if it's an early 70's big block. Once you have it, I can pinpoint the year and size of the truck it came from.
Rick
I realized I gave you the wrong location for the engine code on your big block. It's on the right side of the block just above the water pump mounting at the base of the head, there's a small lip or ledge it's stamped into, the same as the small block. I apologize for that.
The code you're looking for should be a 3 letter sequence, something like TRU, TRS, or similar if it's an early 70's big block. Once you have it, I can pinpoint the year and size of the truck it came from.
Rick
24
For Sale / Wanted / A few carbs for sale.
« Last post by 77cruiser on March 19, 2025, 09:49:11 AM »7027156
17056240
17059253 no sec. rods & hanger
7045230 missing sec. AV shaft
7040511 no sec. rods & hanger
7040202
$25 each + shipping
17056240
17059253 no sec. rods & hanger
7045230 missing sec. AV shaft
7040511 no sec. rods & hanger
7040202
$25 each + shipping
25
Dialing in your rebuilt Quadrajet carburetor / Re: A lot of tips and recommendations to absorb!
« Last post by andyinindy on March 19, 2025, 07:02:24 AM »Your reply absolutely helps my understanding, and your time taken to share your experiences is GREATLY appreciated.
I'll swap out the A/F gauge on the right with a vacuum gauge.
Thanks
I'll swap out the A/F gauge on the right with a vacuum gauge.
Thanks 26
Diagnose a Quadrajet carburetor problem / Re: 17084223 float height
« Last post by 65malibu on March 19, 2025, 06:45:17 AM »The carb didn't have one in it when I rebuilt it. Is that something you sell or should I go scrapping? I will also check the well for hole in casting and possibly stains from leaking at the air horn gasket. Could it be leaking into the cavity where the idle bypass air pulls from? I'm just spit balling here as I don't have the carb apart yet.
27
Diagnose a Quadrajet carburetor problem / Re: 17084223 float height
« Last post by Cliff Ruggles on March 19, 2025, 04:22:44 AM »I used a 1977 Pontiac Q-jet on five different engines that powered my 1973 Ventura and didn't use the clip on the needle or plastic filler in the aneroid location. I logged at least 100,000 miles on that carb and thousands of drag strip runs, with PLENTY of hard braking and power stops and never once did I experience a flooding scenario, and the float was set at 9/32".
I'd add that I used as .145" fuel inlet seat and 8.5 psi fuel pressure.
Even with that said I've had a few complaints over the years where folks experienced momentary flooding when hard braking or panic stops when they left the plastic filler cup out, so if you have one I'd certainly put it in the carb as there are no negatives that I know of from using it.
I've also had a couple of complaints when folks left the clip off the needle that it got "glued" in place when the carb dried up. Makes me wonder what type of fuel they were using that left sticky residue behind to cause that, but for sure if you use the clip and adjust it correctly that's not going to happen if/when you leave the vehicle sit for weeks and months at a time.
Anyhow, adding bowl volume is a complete waste of time/funds and that would be the only reason I can think of to leave out the plastic up on a later carburetor. In any and all scenarios you simply need to keep the bowl full. This means paying attention to fuel delivery and fuel inlet seat diameter not adding more fuel to the bowl......
I'd add that I used as .145" fuel inlet seat and 8.5 psi fuel pressure.
Even with that said I've had a few complaints over the years where folks experienced momentary flooding when hard braking or panic stops when they left the plastic filler cup out, so if you have one I'd certainly put it in the carb as there are no negatives that I know of from using it.
I've also had a couple of complaints when folks left the clip off the needle that it got "glued" in place when the carb dried up. Makes me wonder what type of fuel they were using that left sticky residue behind to cause that, but for sure if you use the clip and adjust it correctly that's not going to happen if/when you leave the vehicle sit for weeks and months at a time.
Anyhow, adding bowl volume is a complete waste of time/funds and that would be the only reason I can think of to leave out the plastic up on a later carburetor. In any and all scenarios you simply need to keep the bowl full. This means paying attention to fuel delivery and fuel inlet seat diameter not adding more fuel to the bowl......
28
Dialing in your rebuilt Quadrajet carburetor / Re: A lot of tips and recommendations to absorb!
« Last post by Kenth on March 19, 2025, 12:58:35 AM »Welcome to the Forums!
Get a 1968 Pontiac Service Manual and follow the procedures outlined.
Oxygen sensors are for computer controlled engine management systems and can possibly be used to see if the A/F ratio is close to target, otherwise they are of no use on a carbureted car.
Use the methods to adjust the carburetor according to the manual and it will work as intended. 1968 and earlier Quadrajets all leak 100% from the bottom plugs. Putting epoxy on them is like putting a Band-Aid on a severed arm. The holes after the plugs are removed must be tapped to install threaded steel plugs as a permanent solution.
Pumping the gas when the carburetor is empty due to evaporation not only tires out your right foot but also ruins the acc pump seal and wears out the throttle plate. To start a cold engine. press and release the throttle to close the choke, then let the starter (and fuel pump) work to fill the carburetor with fresh fuel until the engine starts.
Searching for vacuum leaks with flammable gases is an old mechanic trick to attract customers, the gas gets in wherever there is vacuum and raises the engine rpm even in places where air gets in where it should.
The sure way is to use a flower sprayer and spray water on the suspected spot, if the rpm drops you have found the leak.
This is a small part of what I have found after almost 40 years of screwing and servicing V8s with carburetors and I hope it helps you a little.
Get a 1968 Pontiac Service Manual and follow the procedures outlined.
Oxygen sensors are for computer controlled engine management systems and can possibly be used to see if the A/F ratio is close to target, otherwise they are of no use on a carbureted car.
Use the methods to adjust the carburetor according to the manual and it will work as intended. 1968 and earlier Quadrajets all leak 100% from the bottom plugs. Putting epoxy on them is like putting a Band-Aid on a severed arm. The holes after the plugs are removed must be tapped to install threaded steel plugs as a permanent solution.
Pumping the gas when the carburetor is empty due to evaporation not only tires out your right foot but also ruins the acc pump seal and wears out the throttle plate. To start a cold engine. press and release the throttle to close the choke, then let the starter (and fuel pump) work to fill the carburetor with fresh fuel until the engine starts.
Searching for vacuum leaks with flammable gases is an old mechanic trick to attract customers, the gas gets in wherever there is vacuum and raises the engine rpm even in places where air gets in where it should.
The sure way is to use a flower sprayer and spray water on the suspected spot, if the rpm drops you have found the leak.
This is a small part of what I have found after almost 40 years of screwing and servicing V8s with carburetors and I hope it helps you a little.
29
Dialing in your rebuilt Quadrajet carburetor / A lot of tips and recommendations to absorb!
« Last post by andyinindy on March 18, 2025, 12:48:07 PM »Too Much Information. 😊
Not long ago I bought an all original, number matching 1968 Firebird 400. One of the earliest projects was to rebuild the original 7028265XF QJ to address a few obvious carb issues. This was in the summer of 23. I hope to wrap up the bulk of the restoration soon and focus on optimizing the performance. The first thing I would like to do is verify the carburetor is performing as an OEM should.
On this forum I recently read that someone addressed the fumes smell after turning off the car by switching to Shell Nitrogen infused gasoline. (I do think this made a difference, Thanks)
I read about how the carb bowl can boil away the gas requiring the pedal be pumped more than a few times to fill the bowl. After two days, I do have to pump the gas at least 1 time, and it will often start in the second try. After a week or more it may take 3 possible 4 tries to start. Is this indicative of the fuel having evaporated or leaked? (I did epoxy the well caps during the rebuild.)
I installed a “Narrow Band” A/F mixture gauge in the car, but haven’t installed the correct O2 sensor just yet. Will that be of use, or should this really be a “Wide-Band” gauge? How can this be used to make adjustments or improvements in the QJ? Or should I rent a tailpipe A/F gauge?
I think I also read somewhere that I can spray something on and around the manifold and carb to indicate possible vacuum or other leaks. What was that spray? I would like to confirm there are no hidden issues.
And finally, since the QJ is 57-years old, and about 100,000 miles, are there physical items that may have worn away that I might want to consider replacing.
Not long ago I bought an all original, number matching 1968 Firebird 400. One of the earliest projects was to rebuild the original 7028265XF QJ to address a few obvious carb issues. This was in the summer of 23. I hope to wrap up the bulk of the restoration soon and focus on optimizing the performance. The first thing I would like to do is verify the carburetor is performing as an OEM should.
On this forum I recently read that someone addressed the fumes smell after turning off the car by switching to Shell Nitrogen infused gasoline. (I do think this made a difference, Thanks)
I read about how the carb bowl can boil away the gas requiring the pedal be pumped more than a few times to fill the bowl. After two days, I do have to pump the gas at least 1 time, and it will often start in the second try. After a week or more it may take 3 possible 4 tries to start. Is this indicative of the fuel having evaporated or leaked? (I did epoxy the well caps during the rebuild.)
I installed a “Narrow Band” A/F mixture gauge in the car, but haven’t installed the correct O2 sensor just yet. Will that be of use, or should this really be a “Wide-Band” gauge? How can this be used to make adjustments or improvements in the QJ? Or should I rent a tailpipe A/F gauge?
I think I also read somewhere that I can spray something on and around the manifold and carb to indicate possible vacuum or other leaks. What was that spray? I would like to confirm there are no hidden issues.
And finally, since the QJ is 57-years old, and about 100,000 miles, are there physical items that may have worn away that I might want to consider replacing.
30
For Sale / Wanted / Re: Two (2) knockoff marine Qjets for sale.
« Last post by faredce on March 17, 2025, 07:40:07 PM »Bump.