Author Topic: Evap Canister, hose routing, simplification at all?  (Read 1542 times)

Offline OldsFan

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Evap Canister, hose routing, simplification at all?
« on: August 25, 2020, 12:15:22 PM »
So I finally had some time and was working on my C10 (1985, 305, TH-350C).  I'd like to simplify all of the craziness around the vac lines to the evap canister.  They tee into each other so much, it is hard to tell what's going on. I replaced some of the lines which were shot when I got the truck to try to cut down on vac leaks. 

My question is, is there anything I can do to simplify some of this?  My Olds projects often have just one or two connections to the vac canister, so I feel like something simpler should work.  The C10 has this crazy set of lines which seem to tee into each other a lot and I get the feeling that not all of those connections are leak free.

The truck has to pass an emissions test (sniffer) and they always check the gas tank holds pressure. The clamp off the line marked with the red arrow which is the vapor line from the tank. I don't think they check anything else.

Can I remove or cleanup some of the hoses that route to the canister?  I think the one on my Olds is hooked up to ported vac on the carb and that's about it...
1985 Chevy C10 LWB with bone stock 305
1971 Oldsmobile Cutlass Supreme with Rocket 350

Offline OldsFan

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Re: Evap Canister, hose routing, simplification at all?
« Reply #1 on: August 25, 2020, 12:23:50 PM »
I am also adding in the hose routing as best as I can.  If you look closely, I marked the two larger bore hoses blue and green to try to make it more visible.

One goes through the PCV valve tee and direct to manifold vac. The other goes to the air horn of the carb.  Not sure if that's exposed to vac or not.  Either way, I have no idea if this is how things are supposed to be or if the previous owner did some "creative routing" with the hoses.
1985 Chevy C10 LWB with bone stock 305
1971 Oldsmobile Cutlass Supreme with Rocket 350

Offline JohnnyPopper

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Re: Evap Canister, hose routing, simplification at all?
« Reply #2 on: September 01, 2020, 06:18:33 AM »
Looks like someone did something, there are hoses missing from the vac valve on the T-stat housing... :o

If all your state does is sniff and does not care about visual inspection, then I guess you can move on without restoring the correct circuits.

I would find a diagram of your truck's vac circuit and then make the determination if a PO did some funny stuff.

BTW, my first resto was a '67 Olds Toronado. What a blast for a 22 year old! Rocket 425 V8! I've also done a '66.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline OldsFan

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Re: Evap Canister, hose routing, simplification at all?
« Reply #3 on: September 08, 2020, 11:37:35 AM »
Thanks for responding.  I missed it initially.

Yeah, that was me, actually.  I took the pictures while I was re-routing some wiring and replacing a broken plastic vac line (down to the EFE valve in the passenger's exhaust) and I had the 4-port connector off of there.  It is back now.  :)

I guess I was just wondering how all of this was originally intended to work and why there is so much "stuff" connected to it when my Olds' have always had such a simple hookup from the factory.  Feel like it should need just vac and maybe ported vac signal to keep it closed while you are at idle...

Toronado's are a love / hate for a lot of people. The front-drive with standard engine mounting are just not always liked. Personally, I think they are cool cars and the transmission setup has proven reliable enough. I've helped a local guy with his 68, but have never done one myself.

1985 Chevy C10 LWB with bone stock 305
1971 Oldsmobile Cutlass Supreme with Rocket 350

Offline 1980K20

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Re: Evap Canister, hose routing, simplification at all?
« Reply #4 on: December 12, 2021, 01:31:59 AM »
Hi OldsFan,

What did you end up doing? I'm installing an evap canister where there was none when I purchased the truck. I don't need to pass emissions, I just don't like the gasoline smell in the garage.

The vacuum from the pvc is tee'ed to the purge? Was it house the whole way or tube part of the way?

Thanks,
Mark

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1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350

Offline Chevygold

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Re: Evap Canister, hose routing, simplification at all?
« Reply #5 on: December 12, 2021, 05:11:16 AM »
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

Offline VileZambonie

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Re: Evap Canister, hose routing, simplification at all?
« Reply #6 on: December 12, 2021, 08:50:25 AM »
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.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline 75gmck25

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Re: Evap Canister, hose routing, simplification at all?
« Reply #7 on: December 19, 2021, 01:34:27 PM »
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.

Offline 1980K20

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Re: Evap Canister, hose routing, simplification at all?
« Reply #8 on: December 19, 2021, 01:51:17 PM »
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

Sent from my SM-G965U using Tapatalk
--------------------------------------
1952 International L112 - waiting for EV conversion
1967 Camaro - 250 six cyl, 200-4R
1980 K20 4x4 Fleetside - 350 SBC roller Cam, TH350