73-87 Chevy _ GMC Trucks > Fuel Systems and Drivability

Evap Canister, hose routing, simplification at all?

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Chevygold:
Interesting post, I have the canister which is connected to the vent line from the tanks but have run out of vacuum connections to attach the vacuum connection to. Swapped the Edelbrock it came with for a Holley so lost the servo connection on the carb so had to connect the servo direct to the inlet manifold, then I have vaccum to the dissy and vacuum for the heater controls. Can I tee into any of these without upset correct operation of any devices?
Thanks
Graham

VileZambonie:
I use a three port canister, check valve and tee, very simple to hook up. I've also found that many GM canisters and brackets will work. I grabbed the one out of the 96 Suburban I just stripped and it fit in my 75 Blazer with minimal effort.

75gmck25:
The original Quadrajet in my '75 GMC 350 had a second vacuum port for the evaporative canister, on the lower front of the carburetor next to the large port for the PCV valve hose.  When I switched to an 80's Quadrajet I lost that port and it was not clear where to run the vapor canister purge hose. 

The stock '75 vapor canister only has two ports and my truck had no separate vacuum valve or check valve controlling the system.  My Quadrajet documentation shows the extra front port as a special port for the vacuum canister connection, but there is no explanation of how it works and when it purges the fumes.   I have tried connecting it with a T into the PCV hose and it seemed to work fine, but I wasn't sure that I didn't just create a big vacuum leak. I now have the canister hose connected to a fitting I added on the air cleaner body, so it draws air into the system if needed, and any vapor/smell just goes into the air cleaner and gets pulled into the carburetor.

Anyone know how that older two port vapor canister worked?  Maybe I'm missing a vacuum control valve that was removed long before I got the truck.

1980K20:
Just two minutes ago, I finished installing my evap can. I hope there's no control valve, I just connected straight to the vacuum. Start her up in a bit, all see.

I would like to run my lines differently, and get smaller clamps. But it's a test. We've got one dry day, gotta drive her and see what else to add to the list.

Mark

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