Can you share ported vacuum?
05-22-2017, 01:46 PM
#1
Pro
Thread Starter
Can you share ported vacuum?
Just wondering if you can share a ported vacuum line to the distributor. I ask this question because I don't have an extra ported vacuum on my carburetor baseplate to handle the fuel canister line (thanks Cliff). The only ported vacuum line I have is to the distributor advance. If it is not wise to share the line I need to know how to hook up the fuel canister line then. Right now its just hanging there. I was going to tee off the PCV valve and bought a 2-port type but it affects the carburetor negatively by raising my idle quite a bit. So this won't work. I have yet to try splicing the existing line using my original 1-port PCV and see what that does. Maybe the 2-port design is just a different flow rate...not sure. Anyhow please let me know.
05-22-2017, 03:25 PM
#2
If the car is modified you are better off hooking the distributor to manifold vacuum. What is unclear is what happened to the original set up causing you to ask this question?
05-22-2017, 03:40 PM
#3
Pro
Thread Starter
The car is NOT modified and is stock. I purchased a custom carburetor from Clifford Ruggles but he set me up with a Q-jet baseplate with no fuel canister port! The car was purchased with a Holley and I'm putting her back to stock and had no Q-jet carb to give Cliff.
05-22-2017, 04:04 PM
#4
In that case I see no issue with sharing the one ported line.
05-22-2017, 06:08 PM
#5
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05-22-2017, 08:15 PM
#6
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Why are you staying with ported vacuum to the distributor? The only thing that ported vacuum does is makes it easier to overheat the engine on a hot day.
05-22-2017, 08:33 PM
#7
Pro
Thread Starter
05-23-2017, 08:23 AM
#8
Pro
I think he recommends try both - and use whichever provides the greatest benefit, because all setups are different.
IN my experince, in most cases manifold vacuum at idle, assuming both idle and timing are properly adjusted, provides a smoother idle and a somewhat cooler running engine, but may also result in slight higher emissions. Not sure if that is an issue in Utah.
IN my experince, in most cases manifold vacuum at idle, assuming both idle and timing are properly adjusted, provides a smoother idle and a somewhat cooler running engine, but may also result in slight higher emissions. Not sure if that is an issue in Utah.
05-23-2017, 08:27 AM
#9
Pro
Thread Starter
I think he recommends try both - and use whichever provides the greatest benefit, because all setups are different.
IN my experince, in most cases manifold vacuum at idle, assuming both idle and timing are properly adjusted, provides a smoother idle and a somewhat cooler running engine, but may also result in slight higher emissions. Not sure if that is an issue in Utah.
IN my experince, in most cases manifold vacuum at idle, assuming both idle and timing are properly adjusted, provides a smoother idle and a somewhat cooler running engine, but may also result in slight higher emissions. Not sure if that is an issue in Utah.
05-23-2017, 10:15 AM
#10
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An engine is more thermally efficient at idle when the vacuum advance is connected to manifold vacuum. It idles better (using less fuel!), reduces dieseling tendencies at shutoff, and doesn't overheat as easily. Win, Win, Win.
05-23-2017, 11:02 AM
#11
Pro
Not the original poster, but a related question. So could I use manifold vacuum to operate the vapor canister? My car has the vapor system which is currently not hooked up. I don't have any vacuum ports on my carb to hook up the signal line. Before you ask I really mean it, I do not have any vacuum ports on my Holley DP. My dist does not have vacuum advance. I do have a PCV port on the carb base plate.
Last edited by Crafty12; 05-23-2017 at 11:06 AM.
05-23-2017, 11:37 AM
#12
Team Owner
No, you can't. Or, at least, it's not a good idea.
The vapor canister should only purge its contents when the engine is operating above an idle condition. If it purged at idle, you would get LOTS more air with the idle mixture and it would run terribly. Keep the vapor canister actuator on "ported" vacuum.
The vapor canister should only purge its contents when the engine is operating above an idle condition. If it purged at idle, you would get LOTS more air with the idle mixture and it would run terribly. Keep the vapor canister actuator on "ported" vacuum.
05-23-2017, 12:20 PM
#13
Pro
Thread Starter
No, you can't. Or, at least, it's not a good idea.
The vapor canister should only purge its contents when the engine is operating above an idle condition. If it purged at idle, you would get LOTS more air with the idle mixture and it would run terribly. Keep the vapor canister actuator on "ported" vacuum.
The vapor canister should only purge its contents when the engine is operating above an idle condition. If it purged at idle, you would get LOTS more air with the idle mixture and it would run terribly. Keep the vapor canister actuator on "ported" vacuum.
That was the true intent of my thread as well. The fuel vapor canister line needs ported vacuum. Understood. So the question remains...can you share the ported vacuum line going to the distributor with the fuel canister line if you decide to use ported vac for your distributor?
05-23-2017, 02:42 PM
#14
why dont you hook up a vacuum gauge and verify that it makes no difference if two devices share the port or one
05-23-2017, 03:36 PM
#15
Pro
That was the true intent of my thread as well. The fuel vapor canister line needs ported vacuum. Understood. So the question remains...can you share the ported vacuum line going to the distributor with the fuel canister line if you decide to use ported vac for your distributor?
Sorry to muddy the waters.
