Vacuum
Thread Starter
Instructor
Joined: Feb 2004
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From: Ravenna Ohio
Vacuum
What is up with all of these vacuum lines. There is like a little thing sticking out of my intake and there is two more of them coming off of my thermostat housing. I will be doing a cam head intake and carb swap in a week so which of these lines can i lose.
Josh
Josh
Tech Contributor
Joined: Aug 1999
Posts: 14,380
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From: At my Bar drinking and wrenching in Lafayette Colorado
Temperature-controlled vacuum switches to control operation of your distributor vacuum advance and other emissions-related devices based on engine coolant temp. If you need to pass a visual emissions test, you need to keep them. If not, you can simplify the system.
Thread Starter
Instructor
Joined: Feb 2004
Posts: 241
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From: Ravenna Ohio
How can i do that I am going with some vortec heads and an edelbrock intake with no EGR. A lot of those linea are already disconected. I still have on from manifold to EGR and manifol to carb(below filter passenger side), and manifold to evaporator canister i think. The ones from the thermostat housing are all nearly diconected, the only one still connected goes from the housing to right above the fuel filter. There is also one from the thermo housing that looks like it may have gone to the carb but it is not connected and i don't see anywhere that it may have gone.
Melting Slicks
Joined: Jan 2005
Posts: 3,028
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From: Madison Ms
If I'm not mistaken (mines an 81 without computer), Only vac lines you will need are for the brake booster, head lights, cruise control, and these all come out at the back of the intake (closest to windshield), on a new intake. Ditch the rest if you are desmogging, and dumping the computer, and don't care about emission stuff.....
I started unplugging old lines one at a time and checking by cranking and testing accessories to make sure I didn't screw something up I needed. Wish I could help you more, but I didn't exactly know what I was doing either, and still don't......lol....
I started unplugging old lines one at a time and checking by cranking and testing accessories to make sure I didn't screw something up I needed. Wish I could help you more, but I didn't exactly know what I was doing either, and still don't......lol....
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
JD -
On your '80, here's what you need to have for vacuum hoses:
You need to leave your PCV hooked up to the large fitting on the forward lower base plate on the carb. Power brakes goes into the large screw-in fitting on the back.
Run a hose from your distributor vacuum advance control unit (the "vacuum can") to the vacuum nipple located on the forward driver's side of the carb in the middle of the float bowl. This is straight manifold vacuum on the 1980 carb, and will work well with your vacuum advance (suck on the hose to make sure it's working first).
All accessory hoses (for headlights and heater controls) should come out of a dedicated fitting in the manifold to the rear of the carb. If you're running any accessory hoses off the carb, you need to keep those hooked up.
The hose to the charcoal canister can be left hooked up - it has no adverse effect on performance. You can cap off all other vacuum port nipples on the carb and remove the hose harnesses.
On your '80, here's what you need to have for vacuum hoses:
You need to leave your PCV hooked up to the large fitting on the forward lower base plate on the carb. Power brakes goes into the large screw-in fitting on the back.
Run a hose from your distributor vacuum advance control unit (the "vacuum can") to the vacuum nipple located on the forward driver's side of the carb in the middle of the float bowl. This is straight manifold vacuum on the 1980 carb, and will work well with your vacuum advance (suck on the hose to make sure it's working first).
All accessory hoses (for headlights and heater controls) should come out of a dedicated fitting in the manifold to the rear of the carb. If you're running any accessory hoses off the carb, you need to keep those hooked up.
The hose to the charcoal canister can be left hooked up - it has no adverse effect on performance. You can cap off all other vacuum port nipples on the carb and remove the hose harnesses.
Thread Starter
Instructor
Joined: Feb 2004
Posts: 241
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From: Ravenna Ohio
What happens if you didconnect the one going to the canister. If i can get rid of that one then i could get rid of all of those temp valves. Is it ok to leave it hooked up and leavethe second nipple on the valve open or does it need to be plugged up. Anyway sounds good. I was up late last night reading a few of your tunning papers and vacuum stuff trying to figure out what can stay and go for the upcoming swap. Thanks for the help
Josh
Josh
Last edited by JDRez42; Mar 23, 2005 at 05:01 PM.
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From: Austin Tx
On my 1976 model the vacuum lines at the thermostat housing operate the EGR valve. One line comes from the carb. to the temperature controlled valve (the valve that screws into the thermostat housing) this valve opens the vacuum path to the EGR valve after the engine warms up. The other line obviously goes to the EGR valve.