Vacuum lines on a SBC
09-13-2000, 02:43 PM
#1
Vacuum lines on a SBC
Hi, I've junked the computer controlled carb and distributor on my 83 TA(LG4, 5spd) in favor of a standard Q-jet and HEI. With all the hoses and wires (many of which I don't think I will need any longer) I'm a little confused as to where to run the various lines. Could someone give a wannabe mechanic a few tips? 
09-13-2000, 06:39 PM
#2
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Car: 82 Berlinetta/57 Bel Air
Engine: LS1/LQ4
Transmission: 4L60E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
If the trash hasn't been picked up yet, go get the carb and distributor out of the can and put them in a box for potential future needs. You never know when the EPA will come knocking on your city gates.
That aside, the only necessary vacuum line change, depending upon the vintage of your replacement carb, is the vacuum signal to the replacement distributor. This should come from the vacuum source on the front passenger side of the carb (ported - meaning no vacuum signal until the throttle is off idle). The other lines to the charcoal canister should still hook up, assuming you have an externally vented fuel bowl (large nipple on top front driver's side). Also, some older applications had the power brake line on the back of the throttle body, so make sure that is plugged. You should also use the PCV valve nipple on the front center of the throttle body. The other non-ported vacuum lines should go to the air cleaner snorkle valve (if you retained the factory air cleaner) and the charcoal canister. You should have a vacuum routing diagram on your hood to guide you through most of this (the distributor won't be there).
The only electrical connection to the carb will be the choke thermostat. If your replacement carb has a heated air type thermostat, you should replace it with an electric type and use it. The throttle position and mixture connectors, as well as the 4-wire connector going to the original distributor should be taped out of the way (don't cut them - see "EPA" above). The power and tach wires will be the same on both the original and replacement distributor. Your SES light will come on and stay on, so just take the bulb out.
Having said all that, I don't understand why people don't just work with the computer parts, but then, that's just me.
------------------
82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 3.08 open, cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, World 305 heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.
That aside, the only necessary vacuum line change, depending upon the vintage of your replacement carb, is the vacuum signal to the replacement distributor. This should come from the vacuum source on the front passenger side of the carb (ported - meaning no vacuum signal until the throttle is off idle). The other lines to the charcoal canister should still hook up, assuming you have an externally vented fuel bowl (large nipple on top front driver's side). Also, some older applications had the power brake line on the back of the throttle body, so make sure that is plugged. You should also use the PCV valve nipple on the front center of the throttle body. The other non-ported vacuum lines should go to the air cleaner snorkle valve (if you retained the factory air cleaner) and the charcoal canister. You should have a vacuum routing diagram on your hood to guide you through most of this (the distributor won't be there).
The only electrical connection to the carb will be the choke thermostat. If your replacement carb has a heated air type thermostat, you should replace it with an electric type and use it. The throttle position and mixture connectors, as well as the 4-wire connector going to the original distributor should be taped out of the way (don't cut them - see "EPA" above). The power and tach wires will be the same on both the original and replacement distributor. Your SES light will come on and stay on, so just take the bulb out.
Having said all that, I don't understand why people don't just work with the computer parts, but then, that's just me.
------------------
82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 3.08 open, cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, World 305 heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.
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