I have the gas tank vent line connected to the canister. If I run the outlet of the canister to the carb will it cause problems? What is needed for proper function?
Does the charcoal canister function without AIR pump?
- Thread starter 87CutlassSupremeBrougham
- Start date
You do not need an AIR pump for the canister. Engine size? Assuming 307?
If so, this thread may help.
If so, this thread may help.
I’ve got the valve still. So where do I hook these lines up to? It’s a swap from v6 to sbc327.
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There's usually two things you're venting to the canister, the fuel tank and the fuel bowl of the carburetor.
The other line usually hooks into the intake, or port on the bottom of carb that vents the canister into the engine purging the charcoal of those captured fumes under certain conditions.
The small vacuum line usually controls the valve to open/close based on engine temp through thermo vacuum switch.
Once you change out OEM engine, carb and other emissions controls from what it came with you have to consider the actual theory of how they work, then adapt the component parts to your new configuration.
That info 69hurstolds posted in the link covers it all in great detail.
If you no longer have Rochester OEM carb, you likely don't have fitting for that bowl vent so you may just need to hook up the fuel tank vent line.
The other line usually hooks into the intake, or port on the bottom of carb that vents the canister into the engine purging the charcoal of those captured fumes under certain conditions.
The small vacuum line usually controls the valve to open/close based on engine temp through thermo vacuum switch.
Once you change out OEM engine, carb and other emissions controls from what it came with you have to consider the actual theory of how they work, then adapt the component parts to your new configuration.
That info 69hurstolds posted in the link covers it all in great detail.
If you no longer have Rochester OEM carb, you likely don't have fitting for that bowl vent so you may just need to hook up the fuel tank vent line.
Yeah I dont have the TVS either. But if I only hook up the tank vent wont the canister overload with fumes and cause problems?
Not at all, it's designed to handle the vapors from both the carburetor fuel bowl *and* the fuel tank. The idea is the canister (temporarily) holds on to the tank vapors in the charcoal bits, the purge valve will open under the appropriate conditions, and the line going over to the intake, carb base, or tee'd in to the PVC hose, etc.. will evacuate those vapors from the canister so they get burned in combustion.
That's why it's important on the older ones to replace that pancake filter on the underside of the canister as that it what allows fresh air to enter the canister when the engine vacuum is applied to purge out the vapors. Over time it can get dirty, or clogged and that would impede it's ability to purge the vapors fully. Most often you'll find they're missing anyway because they didn't have originally, or was tossed by someone.
I run Holley EFI on mine, and still vent my fuel tank to the canister, and the purge line goes to the throttle body port. It's the setup that was used back on the 80's & 90's L98 F Body Camaro/Firebird with TPI, very simple canister with just one line IN (from tank) and one like OUT (to intake/throttle body). In fact it doesn't use a filter on bottom, because it's designed differently to filter incoming air without it.
The difference with mine is instead of being controlled with a TVS and ported vacuum signal for the purge valve, my canister has a Evap Purge Electric Solenoid built in which is controlled by the Holley EFI computer. So I programmed it to purge the canister (pulse on the solenoid) anytime I'm in 4th gear, and between 15-30 MPH, and my engine temp is above 140 degrees. It purges for 10 seconds, then will repeat again the next time all the conditions are met again, and so on while the engine is running.
You should still be able to use a TVS, and the Ported VAC purge valve in your case, just cap off the unused port for the carburetor bowl vent. Or maybe use a vacuum purge valve for a later EFI system, so it's just a simple IN/OUT port between canister and intake/carb base/PVC line.
So if I understand this right, I tap 1 into the PCV line, 6 to the vacuum port on carb, 4 comes from the canister and 7 gets capped off?
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So if I understand this right, I tap 1 into the PCV line, 6 to the vacuum port on carb, 4 comes from the canister and 7 gets capped off?
Yup, since you don't have the original carb with the float bowl vent port you would simply cap that off.
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*ported" vacuum is a port on the carb that is "above" the throttle blades, the vacuum increases when you open the throttle.
it's opposite of *manifold* vacuum, which is a port on the intake manifold (or carb base) that is below the throttle blades, and the vacuum decreases when you open the throttle.
typical Holley carb is similar to the pic below.
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