Another tank venting question

[4x4man514]

Ok so I think I have seen this somewhere on here b4 but I cant seem to find it

My 72 has a fully functiining venting system and im putting a efi motor in and im planning on using the can p valve.

My question is the old style can has two vents. One in the center and one more. Do I just plug one and use the other? And which one do I use?



Thanks!

 

[DirtDonk]

None of them get plugged. All will still be utilized.
Do you still have the standard round can style that’s mounted to the frame?
If so, there will be three ports total. The smallest one is the one that gets vented from the gas tank, or in your case the condensing tank in the cabin.
Of the two larger ones, you will somehow connect one to the can-P solenoid valve and the other does not get plugged.
Instead, it remains open to atmosphere with one of those mushroom caps.
Originally it would’ve had one of those fiber and metal reinforced hoses up into the engine compartment, and the venting mushroom cap.
The caps do not close the tube, but merely keep debris out while still allowing venting.

I think you are actually better off replacing the original can style with the 76/77 plastic canister mounted on the firewall.
The primary reason for this is that it has a fourth fitting that is the correct size for your solenoid valve.
Or at least easier to adapt.

 

[4x4man514]

Thanks . Seems like that is what I remember from before.

My question is wouldn't leaving one open allow fumes to come out of the system and into the garage?

 

[DirtDonk]

Theoretically, yes. But you are not really leaving it fully open with a mushroom cap.
It is allowing outside air in, but it’s not a direct path straight up to vent fumes. Even the early style, which was not in fact a cap it was just an open hose did not result in fumes for some reason.
You have to have some thing that allows air in.

Best would be to look at the layout of say a 92 Mustang and see how it’s connected.
Remember, an early style canister was never intended to have direct vacuum applied to it such as you will have with your system.
So maybe there is a reason not to use the old ones?
I just don’t know.
And I can’t remember whether the center hole is the vent, and the side hole goes to the air cleaner or the other way around.