'89 Fifth Ave
- Thread starter Monkeyed
- Start date
kkritsilas
Well-Known Member
No more gasoline talk on Monkeyed thread, maybe start a new thread on gasoline?
Kostas
Kostas
Jack Meoff
Mopar Maniac
Start it up Kostas...
quite alright, I worked for one of the last full service stations in my town during high school. It'ss fascinating how many ppl LOVE ethanol even though they don't have the first clue what it is, or does.
kkritsilas
Well-Known Member
According to the Vaanth list, this is a carb from a 1982 318 pickup truck (9342S), with Bowl Vent (solenoid controlled). Might want to look at having it rebuilt by a TQ expert (look up some of the threads on the TQ, there is a guy who is supposed to be really good with rebuilding them), and having him put in the vacuum port. Then get a distributor with vacuum advance, and disconnect all of the ESA/Lean Burn stuff, and roll up all of the wiring associated with that system. This way, you stay with the same throttle linkage and the cruise control should continue to work (assuming it works now).
Most of the time, the carb type is scribed into the base plate of the TQ, on a vertical pad near the mounting bolt flange, not on a lable. Maybe its a replacement of some sort, or a rebuilt one that a label was added on to.
Kostas
Most of the time, the carb type is scribed into the base plate of the TQ, on a vertical pad near the mounting bolt flange, not on a lable. Maybe its a replacement of some sort, or a rebuilt one that a label was added on to.
Kostas
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seems like it'd almost be cheaper to just get a remanned one, than to have this rebuilt. Maybe they just like to overcharge my face, or something.
the cruise does work, the only things not working on it are the a/c and the lean burn
The 9342S already has a ported vacuum fitting for the vacuum advance. As I'd noted, most truck carbs do. There is no trick to rebuilding that carb; it's got just the bowl-vent solenoid which I explained in my post simply needs to be wired to 12V+ key-on. It is not an ELB/ESA carb nor is it an "emissions" or feedback unit. It's from a truck.
Whomever said that doesn't even know how to connect it correctly. Either that, or they had such a poor-running engine that the carb's idle screw was turned in so far that it was no longer operating on the idle circuit. Vacuum advance is critical to good drivability and economy. The reason you don't see it on later vehicles that still used distributors is because the timing was controlled electronically. Rest assured, the computer was putting the spark in the same places a vacuum advance canister would. That can't be accomplished with mechanical advance alone.
It's not hard to be "really good" with ThermoQuads. The big secret is to just rebuild it per the kit instructions and follow one of the manuals I posted to get it in tune. There are baselines for the secondary air door, but for best operation it needs to be done on the car. Rebuilding the TQ is easy. Easy as any other carb except maybe a 4412 Holley, and much simpler than a QuadraJet. Afraid to tackle it? Ship it to me with a kit and floats and I'll do it for $75 + return shipping, including all the fine-tuning adjustments pointed out in the hyperlinks I posted, except setting up the secondary air door. Secondary air-door tension adjustment can only be done on your engine; I can't help you there. A reman carb will not have any of those adjustments made since they leave that up to the end user. A "reman" is essentially a thrash rebuild with no tuning work done. I've pulled them apart to find the float level wasn't even set--the end user is expected to correct that since it's considered "tuning"--never mind that he has to crack the carb open (and void any warranty) to do it.
$75 to rebuild and tune it is essentially $50/hr for me. I'll take that kind of pay from anyone offering it. I have a carb soak tank and I'm not afraid to use it.
My suggestion is that you try to tackle this yourself. Carburetors are not some form of black magic but people absolutely freak out about ThermoQuads and QuadraJets, which are in my opinion the two best street carbs on the planet (in that order). They require basic hand tools and a little printed guidance, and you're good to go. Set aside a day when you can disassemble it in a set area, soak the components for an hour or two, and reassemble it all in the same day so parts don't get lost and you have the whole process fresh in your mind. Print out one of the tuning guides I posted and follow it to the letter. Bang! You're a ThermoQuad guru with the rest of them. Plus, you have the pride of saying you did it yourself and you saved yourself a ton of money in the process. At the very worst, you're no worse off than you were. Send me the box with all the parts, and a check, and I'll do the rebuild for the same price unless I have to source missing/damaged metering rods, screws, etc. I don't think it would come to that with just a little attention and care taken on your part.
Wherever you got that information, never refer to it again. If it was a magazine, burn it and don't ever buy it again. If it was a website, delete the bookmark and never return. If it was a friend, don't ever ask him about anything car-related ever again. In fact, don't ride in his car. He may not know enough to recognize a bad ball joint.Monkeyed said:
Whomever said that doesn't even know how to connect it correctly. Either that, or they had such a poor-running engine that the carb's idle screw was turned in so far that it was no longer operating on the idle circuit. Vacuum advance is critical to good drivability and economy. The reason you don't see it on later vehicles that still used distributors is because the timing was controlled electronically. Rest assured, the computer was putting the spark in the same places a vacuum advance canister would. That can't be accomplished with mechanical advance alone.
It's not hard to be "really good" with ThermoQuads. The big secret is to just rebuild it per the kit instructions and follow one of the manuals I posted to get it in tune. There are baselines for the secondary air door, but for best operation it needs to be done on the car. Rebuilding the TQ is easy. Easy as any other carb except maybe a 4412 Holley, and much simpler than a QuadraJet. Afraid to tackle it? Ship it to me with a kit and floats and I'll do it for $75 + return shipping, including all the fine-tuning adjustments pointed out in the hyperlinks I posted, except setting up the secondary air door. Secondary air-door tension adjustment can only be done on your engine; I can't help you there. A reman carb will not have any of those adjustments made since they leave that up to the end user. A "reman" is essentially a thrash rebuild with no tuning work done. I've pulled them apart to find the float level wasn't even set--the end user is expected to correct that since it's considered "tuning"--never mind that he has to crack the carb open (and void any warranty) to do it.
$75 to rebuild and tune it is essentially $50/hr for me. I'll take that kind of pay from anyone offering it. I have a carb soak tank and I'm not afraid to use it.
My suggestion is that you try to tackle this yourself. Carburetors are not some form of black magic but people absolutely freak out about ThermoQuads and QuadraJets, which are in my opinion the two best street carbs on the planet (in that order). They require basic hand tools and a little printed guidance, and you're good to go. Set aside a day when you can disassemble it in a set area, soak the components for an hour or two, and reassemble it all in the same day so parts don't get lost and you have the whole process fresh in your mind. Print out one of the tuning guides I posted and follow it to the letter. Bang! You're a ThermoQuad guru with the rest of them. Plus, you have the pride of saying you did it yourself and you saved yourself a ton of money in the process. At the very worst, you're no worse off than you were. Send me the box with all the parts, and a check, and I'll do the rebuild for the same price unless I have to source missing/damaged metering rods, screws, etc. I don't think it would come to that with just a little attention and care taken on your part.
http://www.corvetteactioncenter.com...ported-vs-manifold-source-vacuum-advance.html
I meant ported vs. manifold vacuum, I guess I wasn't as clear as I meant. The question to me was whether it was even worth it to add a port, but that's moot if it already has one, the next point would be which is better to use.
from that source
"Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.
If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more."
"Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.
If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more."
How did I know this was somehow going to come back to a Chevrolet guy? :eusa_doh:He's wrong, wrong, wrong.
Never, ever use straight manifold vacuum. The timed (ported) spark port was invented solely for the reason of vacuum advance. Using constant vacuum is what causes inconsistent idle.
Never, ever use straight manifold vacuum. The timed (ported) spark port was invented solely for the reason of vacuum advance. Using constant vacuum is what causes inconsistent idle.
It can be a topic for another day lol. :thumbsup:
already had a casualty..
the tiny little bolt that goes on the end of this sheared off
I got all of the screws out, but it still won't come apart, gaskets sticking? Don't want to pry and crack something..
I may just take you up on that offer, I'd say I'm fairly knowledgeable, but not terribly experienced. Might be something best left to an expert. I see things like "Slowly open the primary throttle valves the specified distance from the throttle bore walls." Then no specification listed? hmm, very helpful.. Glad I got my degree in this, and all of my State certs.. Which rebuild kit do you recommend/prefer?
Hint: look behind the secondary air valve (the big-ass "choke flap").
I hate to tell you this, but there really was no reason to attempt to remove the screw you broke. You really don't need to tear apart any of the linkage except for removing the link rods to disassemble the three main sections.
I hate to tell you this, but there really was no reason to attempt to remove the screw you broke. You really don't need to tear apart any of the linkage except for removing the link rods to disassemble the three main sections.
Fortunately it doesn't seem to have had any effect, it broke short enough that the piece is still firmly attached.
Not sure what I'm supposed to be seeing behind the secondary,
BUT, it does look like a little piece is cracked off in there, may or may not matter..
Doh... there I getting mixed up again. I was thinking of the main-body screws behind the primary choke plate toward the secondary side, which you've gotten out already. It looks like you've got all 10 screws out so it should split open. Hold down the throttle body at the rear mounting tabs with your fingers and push up on the air horn with your thumbs. It might take some effort, but it should split.
That chipped-off piece inside is just the boss for the air-cleaner stud. It doesn't look like it should cause a problem since the threads go pretty deep.
Don't remove the secondary air door or the throttle butterflies or shafts. That's just going way further than necessary and opening a can of worms for potential failure. Realistically, you shouldn't have even taken out the choke plate. When you reinstall it, use red threadlocker on the butterfly screws so they don't vibrate out and fall into your engine.
That chipped-off piece inside is just the boss for the air-cleaner stud. It doesn't look like it should cause a problem since the threads go pretty deep.
Don't remove the secondary air door or the throttle butterflies or shafts. That's just going way further than necessary and opening a can of worms for potential failure. Realistically, you shouldn't have even taken out the choke plate. When you reinstall it, use red threadlocker on the butterfly screws so they don't vibrate out and fall into your engine.
Roger that. I have a couple things of blue laying around, I'll pick up some red before I get to that point. I just took that off to get the linkage out of the way to get to the one screw a little easier.
yeah, no.. I tried holding the bottom mounting tabs with my left hand, and grabbing the fuel inlet rails with my right, and pushing/pulling as hard as I could, didn't budge. I bolted it back on the intake and used a small pry bar, and managed to get the bottom section to seperate. But, now there's no way to get the middle and the top apart without jamming a screw driver in between them and cracking the phenolic to bits. Might drown it in Mineral Spirits and hope for the best.....
