Adding vent to sending unit or charcoal canister

[applebmw]

Anyone add a vent to there in cab gas tank sending unit? Installing Holley Sniper and my tank has no vents or return lines....
OR...added a charcoal canister if I use sump unit, seems to be best in my mind. If I buy new tank, it will be rear top fill unit, cha-ching..trying to keep from throwing $$$ at it.......

[Andy4639]

Originally Posted by applebmw

Anyone add a vent to there in cab gas tank sending unit? Installing Holley Sniper and my tank has no vents or return lines....
OR...added a charcoal canister if I use sump unit, seems to be best in my mind. If I buy new tank, it will be rear top fill unit, cha-ching..trying to keep from throwing $$$ at it.......

Most cab tanks have a vent line. It goes up the back side of the cab on the passenger side and back down to the tank.

[Steeveedee]

Originally Posted by Andy4639

Most cab tanks have a vent line. It goes up the back side of the cab on the passenger side and back down to the tank.

That system is used as a vapor separator for the fuel tank, so that raw fuel won't end up in the vapor canister. My '70 does not have it. I think that it was installed on '72 and up trucks.

Someone who has installed this setup will be along eventually to tell you how they did it.

[applebmw]

Originally Posted by Steeveedee

That system is used as a vapor separator for the fuel tank, so that raw fuel won't end up in the vapor canister. My '70 does not have it. I think that it was installed on '72 and up trucks.

Someone who has installed this setup will be along eventually to tell you how they did it.

Believe you are correct, looking at tank replacement, 72 has vent in them, they can be bought for 70 truck, but if spend $$ on new tank, it is going in the back. Hoping someone can tell me how to add charcoal canister......

[Jrainman]

I have done this , I first tried it by buying a 72 sending unit to utilize the vent that is already there ,but the sending unit only lasted about 2 months before it went bad giving me bad fuel gauge readings and I bought the better one (brass Float) vs plasic float .

I ended up drilling , tapping and then soldering over a brass fitting in my original sending unit , No problems at all . in the picture you can see were I put the bulkhead fitting in for the return line, above to the left of the sending unit , the vent hose runs to the passenger door ,I pulled out the upper rubber grommet door stop and put the vent line through that exsisting hole, fit 1/4 hose perfectly and vents with no issues.

[Andy4639]

My 71 C-10 had all of this in it factory. I took it out when I did the 305 TPI years ago. I put the tank in the bed and ran vent lines so no need for the canister.

The canister is only to keep the gas smell down when venting.
Found this on the H.A.M.B site
vent line should be 1/4" , and have atleast two large 3" loops in it the loops helps prevent the vapors from coming out as they are heavy and settle in the bottom of it . you can install a electric valve in the vapor line that opens when the ignition is keyed on ( did this for one car ) its a tank switching valve from a chevy 78 k 20 truck it has no vent option as its non emissions ( exempt for time ) also have done vapor canisters from late model vehicles as they are smaller and cheaper new . 4th gen impala works good .

[applebmw]

Originally Posted by Andy4639

My 71 C-10 had all of this in it factory. I took it out when I did the 305 TPI years ago. I put the tank in the bed and ran vent lines so no need for the canister.

The canister is only to keep the gas smell down when venting.
Found this on the H.A.M.B site
vent line should be 1/4" , and have atleast two large 3" loops in it the loops helps prevent the vapors from coming out as they are heavy and settle in the bottom of it . you can install a electric valve in the vapor line that opens when the ignition is keyed on ( did this for one car ) its a tank switching valve from a chevy 78 k 20 truck it has no vent option as its non emissions ( exempt for time ) also have done vapor canisters from late model vehicles as they are smaller and cheaper new . 4th gen impala works good .

On Canister, they still call for a vent line to tank? don't they? If not... What should I look for? 70's Impala Charcoal Canister??

[applebmw]

Originally Posted by Jrainman

I have done this , I first tried it by buying a 72 sending unit to utilize the vent that is already there ,but the sending unit only lasted about 2 months before it went bad giving me bad fuel gauge readings and I bought the better one (brass Float) vs plasic float .

I ended up drilling , tapping and then soldering over a brass fitting in my original sending unit , No problems at all . in the picture you can see were I put the bulkhead fitting in for the return line, above to the left of the sending unit , the vent hose runs to the passenger door ,I pulled out the upper rubber grommet door stop and put the vent line through that exsisting hole, fit 1/4 hose perfectly and vents with no issues.

Thanks