Q-JET QUESTIONS
10-10-2003, 09:00 AM
#1
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Q-JET QUESTIONS
Hello corvette friends I have just installed a rebuilt Q-jet and every thing is looking good at the moment until the time to hook up the vacuum hoses the pvc hose is fine but the carb. only has 1 port to connection at the front L/side for the advance at the dist. Can I also connect the hose from the charcoal canister to this same vacuum port with a tee piece connection? Also do I need to hook up the spring assist. choke system for the carb. to operate properly? as I do not have a choke thermostat coil spring on the motor thank-you :cheers:
10-10-2003, 12:41 PM
#2
Melting Slicks
Re: Q-JET QUESTIONS (Rob vette)
Rob: I'll take a shot at your questions and if I'm wrong then I'm sure others will correct me. Not knowing the year of your carb or manual vs automatic tranny, I'd hook my pvc vac hose to one of the ports BEHIND the carb. My 79 w/auto has two: one for the power brakes and the other controls the air intake breather flaps. In my case, I'd choose the one to the breather and tee off of it. If you hooked to the front port that also controls your distributor advance, then you might get into timing issues.
As far as adding a spring to your choke, the "spring" on my 79QJet is actually the bimetal device that actually opens and closes the choke. Any other kind of spring simply will not work. If your original bimetal "spring" is missing, then you'll either have to replace it or hook up the ole manual pull type choke cable. Does anyone know if an aftermarket electric choke is available for our QJets?
Hope I've helped :cheers:
As far as adding a spring to your choke, the "spring" on my 79QJet is actually the bimetal device that actually opens and closes the choke. Any other kind of spring simply will not work. If your original bimetal "spring" is missing, then you'll either have to replace it or hook up the ole manual pull type choke cable. Does anyone know if an aftermarket electric choke is available for our QJets?
Hope I've helped :cheers:
10-10-2003, 12:57 PM
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Re: Q-JET QUESTIONS (Rob vette)
Rob -
Your '71 carb should have a vacuum port nipple sticking out of the passenger side of the carb body right in the choke pulloff diaphragm mounting area. Look closely for a hole right there: often rebuilt carbs will have the vacuum hole, but the nipple will be missing (causing a vacuum leak). If you have a missing nipple, install one and use this for accessory manifold vacuum.
Your PCV needs to be hooked up to the large forward nipple in the base of the carb - sounds like you found that one okay. Most early Q-Jets do not have a rear vacuum port for power brakes, so your carb most likely has no vacuum source holes in the back.
The driver's sde forward vacuum nipple is ported vacuum for your distributor vacuum advance. Do not "tee" into this with a constant-bleed accessory such as the evaporative control system, as this constant vacuum bleed will not allow an accurate signal to be sent to the vacuum advance control unit and your timing will run retarded. Keep only the vac advance on that forward driver's side nipple.
If, for any reason, you do not have a vacuum nipple location on the passenger side of the carb as I described above (I've never seen an early Q-Jet without this feature), you can "tee" into the short hose running to the choke pulloff diaphragm. The pulloff will operate just fine even with a bleed source such as the evaporative system hooked up.
You do not need to hook up the divorced choke coil for the carb to operate correctly, but the car will be hard to start and balky when cold. Also, if you do not hook up a choke rod to the choke lever, you need to take a piece of wire and wire the choke fast idle cam securely down to the carb casting standoff. If you do not do this, the choke linkage and choke system tends to flop towards the closed position on hard acceleration, and this will allow the secondary lockout lever to engage, thus preventing secondary throttle opening.
Your '71 carb should have a vacuum port nipple sticking out of the passenger side of the carb body right in the choke pulloff diaphragm mounting area. Look closely for a hole right there: often rebuilt carbs will have the vacuum hole, but the nipple will be missing (causing a vacuum leak). If you have a missing nipple, install one and use this for accessory manifold vacuum.
Your PCV needs to be hooked up to the large forward nipple in the base of the carb - sounds like you found that one okay. Most early Q-Jets do not have a rear vacuum port for power brakes, so your carb most likely has no vacuum source holes in the back.
The driver's sde forward vacuum nipple is ported vacuum for your distributor vacuum advance. Do not "tee" into this with a constant-bleed accessory such as the evaporative control system, as this constant vacuum bleed will not allow an accurate signal to be sent to the vacuum advance control unit and your timing will run retarded. Keep only the vac advance on that forward driver's side nipple.
If, for any reason, you do not have a vacuum nipple location on the passenger side of the carb as I described above (I've never seen an early Q-Jet without this feature), you can "tee" into the short hose running to the choke pulloff diaphragm. The pulloff will operate just fine even with a bleed source such as the evaporative system hooked up.
You do not need to hook up the divorced choke coil for the carb to operate correctly, but the car will be hard to start and balky when cold. Also, if you do not hook up a choke rod to the choke lever, you need to take a piece of wire and wire the choke fast idle cam securely down to the carb casting standoff. If you do not do this, the choke linkage and choke system tends to flop towards the closed position on hard acceleration, and this will allow the secondary lockout lever to engage, thus preventing secondary throttle opening.