Vacuum hose connections on 73 L82 for the evap canister
04-21-2015, 05:35 PM
#1
Vacuum hose connections on 73 L82 for the evap canister
Finally installed the correct p/n Q-jet on my 73 L82 4-sp. And there are several vacuum ports on this carb.
The engine no longer has the AIR pump or EGR valve, so I’m running the manifold-vacuum port on the passenger side to the distributor and I’ll block the other carb ports that are not used.
Can anyone confirm that the valve on top of the canister uses ported vacuum for the small hose?
I assume it does because it already has a manifold vacuum line running to it (tee’d into the vacuum line running to the PCV valve).
It seems to make no sense to run two hoses with the same vacuum levels. Also, I‘d guess the valve is designed to remain closed until the engine is running at at least part throttle so as not to lean out idle or starting.
I’ve checked the factory service manual, assembly manual , NCRS manual and the forum posts but found no useful info on this so far.
One diagram appears to show the small hose going to the front driver's side of the carb. That is ported and goes fairly quickly up to full manifold vacuum as the throttle is moved off idle.
But the port on the carb plate on the passenger side is also ported, although it takes a much larger throttle opening to produce vacuum and it only goes to 10 in.
The engine no longer has the AIR pump or EGR valve, so I’m running the manifold-vacuum port on the passenger side to the distributor and I’ll block the other carb ports that are not used.
Can anyone confirm that the valve on top of the canister uses ported vacuum for the small hose?
I assume it does because it already has a manifold vacuum line running to it (tee’d into the vacuum line running to the PCV valve).
It seems to make no sense to run two hoses with the same vacuum levels. Also, I‘d guess the valve is designed to remain closed until the engine is running at at least part throttle so as not to lean out idle or starting.
I’ve checked the factory service manual, assembly manual , NCRS manual and the forum posts but found no useful info on this so far.
One diagram appears to show the small hose going to the front driver's side of the carb. That is ported and goes fairly quickly up to full manifold vacuum as the throttle is moved off idle.
But the port on the carb plate on the passenger side is also ported, although it takes a much larger throttle opening to produce vacuum and it only goes to 10 in.
04-21-2015, 06:45 PM
#2
Team Owner
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Hi SR,
Here's the stock positions for the hoses on my 71 q-jet.
You can see the large hose marked GM in red and the smaller white striped hose.
I don't know if this applies to your 73 or not but it's something for you to consider.
Regards,
Alan
Here's the stock positions for the hoses on my 71 q-jet.
You can see the large hose marked GM in red and the smaller white striped hose.
I don't know if this applies to your 73 or not but it's something for you to consider.
Regards,
Alan
04-21-2015, 08:53 PM
#4
Burning Brakes
The correct connections are marked on the top of the canister.
Donnie
04-21-2015, 09:01 PM
#5
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Hi SR,
Yes both hoses go to the vapor canister.
As Donnie's picture shows the large hose makes a brief stop at the PCV valve while the small hose goes directly.
Regards,
Alan
Yes both hoses go to the vapor canister.
As Donnie's picture shows the large hose makes a brief stop at the PCV valve while the small hose goes directly.
Regards,
Alan