ukcats07 Posted September 26, 2015 Share Posted September 26, 2015 My setup is a stock 73 tank with a Walbro 255 and corvette FPR feeding a 5.3L. I have tapped the drain plug for 6an feed line and I'm using the original feed line as the return from the FPR. I've had the classic garage stinks of gas smell overnight problem, so I have replaced the vent lines #5 and #6 and capped #14. My return line is going to #10 from the FPR and I have #11 capped. I've double-looped #13 and I have a filter to put on it if need be. Assuming no leaks elsewhere, should this fix my gas venting smell issue? Am I overlooking anything big/unsafe with how I have my fuel lines setup? Thanks Quote Link to comment Share on other sites More sharing options...
z240 Posted September 26, 2015 Share Posted September 26, 2015 You need a large vent line (1/2 - 5/8) attached to the nipple just inside the fill neck while filling the tank to prevent annoying pump shut off and slow filling, and a small (1/4 ish) line while running to replace air while running the engine and draining the tank. Many have said the vent in your fuel cap should even be enough for that. Conventional previously posted methods use the two top vent lines (rear one to the fill neck and the front one to the stock tank vent hard line) and cap the one at the far drivers (left side). Quote Link to comment Share on other sites More sharing options...
ukcats07 Posted September 27, 2015 Author Share Posted September 27, 2015 Just to be clear, this is my setup in a picture. The red lines are capped and the black squiggly line is the double loop I was referring to. Thanks Quote Link to comment Share on other sites More sharing options...
Miles Posted September 27, 2015 Share Posted September 27, 2015 The long red line should not be capped. As the tank is filled air will be trapped in the top of the tank. Connect the long red hose to the fitting near the top of the filler hose to release air trapped in the top of the tank. This is ASSUMING that you have eliminated the vapor tank. There is a post with pictures showing which hoses to keep if you decide to eliminate more hoses. I have eliminated all of the other hoses and have no gas odor. Quote Link to comment Share on other sites More sharing options...
ukcats07 Posted September 27, 2015 Author Share Posted September 27, 2015 The long red line should not be capped. As the tank is filled air will be trapped in the top of the tank. Connect the long red hose to the fitting near the top of the filler hose to release air trapped in the top of the tank. This is ASSUMING that you have eliminated the vapor tank. There is a post with pictures showing which hoses to keep if you decide to eliminate more hoses. I have eliminated all of the other hoses and have no gas odor. I have not eliminated the vapor tank, assuming you're speaking about the metal tank behind the panel. My setup looks exactly as you see it above. Any reason why the air in the tank would not just pass through the other two vent lines into the vapor tank? Quote Link to comment Share on other sites More sharing options...
Miles Posted September 27, 2015 Share Posted September 27, 2015 I had gas fume problems before doing the v8 swap. My engine was carbed so I decided to eliminate as many fume exit points as possible. I eliminated the vapor tank and all of the hoses except for the top hose that I ran to the top fitting on the filler hose. No gas odor since then. Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 2, 2015 Share Posted October 2, 2015 The 1973 Z had a sealed tank system with Crankcase Accumulation of Evaporative Emissions, using bimetallic vacuum switches in the air cleaner and a diverter valve on the left inner fenderwell to determine where the tank vent/vacuum relief would be sourced. If you want to forego that setup you can retrofit something like a Geo Metro EVAP Canister. It's relatively simple vacuum routing that you can adapt to your current air cleaner setup. Long and short of it, taking those hoses off and running an open system invites you dumping all sorts of hot fuel vapors all over your garage after shutdown. The system needs to do a few things: Vent the vapors to a containment area (crankcase or charcoal canister) after hot shut down, and allow air into the tank when running down the road and sucking fuel out with a sealed gas cap. Most EVAP canisters have the diverter valve built into them, with simple routing molded into the caps: "TANK" "DIST""FILTER" From your SEALED system in back (take out the looped line and filter, put it back where it was) run the EVAP "TANK" vacuum line to the EVAP Line on the left inner fender that used to have the diverter valve on it. Run "FILTER" to the air cleaner--or re-use your little filter from out back up front on the Charcoal Canister--that is where it will suck air IN when you;re driving down the road. The DIST is to an engine vacuum source... that will purge the canister after startup and while running regenerate the adsorbant charcoal by flowing clean air over it from the little gauze filter on the bottom. That should do it. Quote Link to comment Share on other sites More sharing options...
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