do i need these vacuum lines
Freshman User
Joined: Jun 2002
Posts: 47
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do i need these vacuum lines
>I'm swapping my old 400 for a new one. My question is do i
>need these vacuum lines and what purpose do they cause.
yes you will need some of them, unless you like shifting a auto like a manual. one should go to the brake booster if you have power brakes. some of the lines were an attempt to reduce emissions from the factory. most of them can be removed. i now mine is a goofy set-up with vacuum lines running from different sensors up to lines coming off the carb. while i never understoood the necessity for all the lines i wouldn't go ripping them off. i'm pretty sure it will kill the vaccuum needed for the vacuum advance on the distributor.
and could also hurt vacuum enough that an auto tranny won't shift right. just my 2 cents.
later.......:P
>need these vacuum lines and what purpose do they cause.
yes you will need some of them, unless you like shifting a auto like a manual. one should go to the brake booster if you have power brakes. some of the lines were an attempt to reduce emissions from the factory. most of them can be removed. i now mine is a goofy set-up with vacuum lines running from different sensors up to lines coming off the carb. while i never understoood the necessity for all the lines i wouldn't go ripping them off. i'm pretty sure it will kill the vaccuum needed for the vacuum advance on the distributor.
and could also hurt vacuum enough that an auto tranny won't shift right. just my 2 cents.
later.......:P
Senior User
Joined: Dec 2001
Posts: 356
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From: space city
do i need these vacuum lines
[updated:LAST EDITED ON 26-Jul-02 AT 06:02 PM (EST)]they do all sorts of different things:
cruise control
EGR valve
charcoal can purge
ignition vacuum advance
smog pump diverter valve(s)
auto tranny modulator
the butterfly in the stock air filter housing that makes it take air off the exhaust manifold until the engine warms up
BRAKE BOOSTER!
choke?
interior ventilation diverter (defrost vs. dash vents vs. floor vent)
heater valve
judging by the spaghetti of tubing on a stock motor, there's probably a lot more than they, but that's all i can think of. it's not necessarily i hose per device either - some of them go to "control logic" devices, like the "reverse vacuum" source - it has no vacuum when there is regular vacuum, and has strong vacuum when regular vacuum is low. i think it's used for ignition retard(?) there are also valves in the vacuum system that open or close at a certain temperature. those are the little "trees" that have the "3 vacuum line" plugs on them. also some on the air filter housing. these could do things like kill the vacuum signal to the ignition vacuum advance if the motor starts to overheat. who knows - it's a big can o' worms!
back in the late 80's, when i "souped up" my car i got rid of all that "mystery" stuff - everything except cruise control, vacuum advance, brake booster, interior ventilation hookup, and heater valve.
these days they supposedly require (around houston) ALL the stock stuff to be there. if the car is less than 25 years old, they also put it on a dyno and measure the emissions UNDER LOAD and DURING ACCELERATION...
the ol' hot rod hasn't been running for a while, and since it's over 25 years old i won't have to get the emissions tested (or maybe they test but it doesn't have to pass) when i get it going again. but from what i understand, they WILL look for the stock stuff. i have an idea it'll just need the "big" stuff - EGR, cats, smog pump, charcoal can... - but i'm saving the stock carb, intake, and all that spaghetti - just in case.
cruise control
EGR valve
charcoal can purge
ignition vacuum advance
smog pump diverter valve(s)
auto tranny modulator
the butterfly in the stock air filter housing that makes it take air off the exhaust manifold until the engine warms up
BRAKE BOOSTER!
choke?
interior ventilation diverter (defrost vs. dash vents vs. floor vent)
heater valve
judging by the spaghetti of tubing on a stock motor, there's probably a lot more than they, but that's all i can think of. it's not necessarily i hose per device either - some of them go to "control logic" devices, like the "reverse vacuum" source - it has no vacuum when there is regular vacuum, and has strong vacuum when regular vacuum is low. i think it's used for ignition retard(?) there are also valves in the vacuum system that open or close at a certain temperature. those are the little "trees" that have the "3 vacuum line" plugs on them. also some on the air filter housing. these could do things like kill the vacuum signal to the ignition vacuum advance if the motor starts to overheat. who knows - it's a big can o' worms!
back in the late 80's, when i "souped up" my car i got rid of all that "mystery" stuff - everything except cruise control, vacuum advance, brake booster, interior ventilation hookup, and heater valve.
these days they supposedly require (around houston) ALL the stock stuff to be there. if the car is less than 25 years old, they also put it on a dyno and measure the emissions UNDER LOAD and DURING ACCELERATION...
the ol' hot rod hasn't been running for a while, and since it's over 25 years old i won't have to get the emissions tested (or maybe they test but it doesn't have to pass) when i get it going again. but from what i understand, they WILL look for the stock stuff. i have an idea it'll just need the "big" stuff - EGR, cats, smog pump, charcoal can... - but i'm saving the stock carb, intake, and all that spaghetti - just in case.
New User
Joined: Jun 2002
Posts: 20
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From: Mankato USA
do i need these vacuum lines
[updated:LAST EDITED ON 26-Jul-02 AT 06:21 PM (EST)]live in minnesota don't have any emission test to my knowledge. i took off the two plugs that go to the radiator hose. the basically run the emission devices. just look to see where they all go. took out the air pump valve and closed the hole that leads to intake. you have to be vary careful of what you do. i took the vacume line on the front of the carb and connected it dirrectly to the vacume advance. the only reason i did this is because i plan on puting edelbrock intake, carb, and cam valvetrain stuff on. if your going to leave the engine the stock i wouldn't mess with the stuff.
