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Discussion Starter · #1 ·
my 56 chev. with 283 ci has no venting on my gas tank, and never came with one. i have a new gas tank, and dont want to remove it and drill holes in it. I want to put an evap cannister on for fumes. i just overhauled the engine, and have no gas leaks anywhere, but need to do this for fumes. I probably can get cannister and other pieces from junk yard. This may sound mickey moused, but I think I can drill and hook up a connection through my gas cap to vent tank. and than put in other pieces to vapor cannister. Any help welcomed. Thanks
 

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when I did my 'chopped '48 Dodge' , I think I used the filler neck, separated from the gas tank by a rubber hose, drilled and welded a vent tube along side , just under the fill cap at bit, and a rubber hose to go on down and under the the body. I'll see if I can find some photos.....
 

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It's a good idea to vent it. Years ago, I parked my 86 Olds cutlass so I could do the engine swap. I got the new engine in and all of a sudden it had all kinds of fuel pressure problems. I was just about blowing carbs apart from excessive pressure. The system was the same as before so I couldn't figure out what all of a sudden caused the problem. I suspected the cam lobe on the cam was ground wrong, so I removed the cam and got another one. This didn't solve anything. Next I went and got a fuel pressure gauge, it went up to 15 psi. Not even a minute after starting it, the fuel pressure would shoot to the max position of 15 psi, and it would sit on it hard as if it was trying to gain more. I tried all kinds of stuff trying to figure out the problem. I even spoke to guys all over the country hopeing I could get some insight but nobody seemed to have the answer. It was around that time I joined this site trying to find the answer. Sure, I installed a fuel pressure regulator, but the pressure was building up so high it was overcoming it as well. I had figured out it was some kind of vent issue, so I removed the plug going to the vapour line and it didn't help. So I looked in all the parts books and the parts store, trying to find someone who sold a vented gas cap. I ordered one which said it was vented. When it arrived I found it was called a "pre vent" which means it only did so sometimes, apparently not very often cause the problem persisted. I found if I left the gas cap off, the pressure didn't build up. I was just about ready to remove the fuel tank and look at the sending unit, I figured if the factory vapour line's check ball was stuck so I tried one last ditch effort. I plugged the fuel line going to the carb. Made sure the gas cap was on tight, grabbed the vapour line and put the air to it. First of all I just got alot of air blowing right back out but I kept at it until finally I heard the tank make a loud pop and the line started accepting the air. I repeated the process several times and each time it would pop. So next I left the vapour line open, and fired the car up. The fuel pressure was way low, around 1 psi. I raised it to 5 on the fuel pressure regulator and it stayed there from that point on. The mistake I made was when I did the engine swap, I plugged the fuel and the vapour line. The fuel in the tank on hot days causes it to expand, the pressure couldn't escape so it forced the check ball in the vapour line closed and it was stuck in position. I was happy the problem was finally fixed after 6 months of pulling my hair out. But it didn't matter, the excessive flooding had ruined the rings in the fresh engine. I drove it for a few years afterwards, but it was down on power and used oil.
The downside was now that the vapour line stayed open when I would shut the car down you could smell the fuel vapour which concerned me. So I started doing all kinds of weird experiments with vacuum lines but I couldn't limit the vacuum low enough to stop it from causing the fuel cap from hissing from it pulling in vacuum. So finally I got a vapour solenoid off a TBI truck and ran a line from it to the aircleaner. I connected it to a switched on power source so it was open while the car was running but would close when shut off. The air coming in the aircleaner when the car was running would create a real small vacuum effect and pull the vapour into the incoming air so the engine could breathe it in and combust it when going down the road. And since it shut off when the switch was off no more fuel vapour smell. Needless to say it was a hodge podge, but it worked.
 

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Discussion Starter · #4 ·
Thanks for replies. Wow, Double Vision, what an ordeal you went through!
And Knighthawk, I would really like photos if you can find some. Also, what did you do for vapor cannister and associated parts to control vapor? Thanks
 

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Justin
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In Jegs or Summit I saw a filler neck adapter that is for fuel injection conversions that have a port for a fuel return line. I wonder if this would work for a vapor recovery system. It would be far enough from the fuel you would just get vapor.

I tried to look for it, but not sure exactly what it is called so the search was endless.


Assuming you have room to install this, it would be a clean installation.
 

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Discussion Starter · #6 ·
Hi Justin, a filler neck slip on with a vent attached sounds workable if there is one for my size filler neck. I may be able to drill my neck and epoxy a vent line on neck if I get a 90 degree drill adpt. I`ve got to conquer this gas fume problem somehow. Any help appreciated. Thanks
 

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vapers ? what vapers? I just needed a vent ! seriously, my reason for doing this was, my gas tank filler is in the trunk. I used a non vented cap and outside vent , and didn't want any vapers in the trunk, so it's vented down under by the tank mounts. I'll see if I can take picture tommorrow
 

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Discussion Starter · #8 ·
thanks for that picture Knighthawk. I plan on drilling my filler neck like that, but I want to go to junk yard and get the vapor cannister and other assc. parts for vapor recovery. I hope I can get parts off a 1970s vehicle and hook things up correctly. If I understand the system, and hope someone will tell me if I`m wrong, but #1, from the vent line, in my case at the filler neck, the vent line runs to the cannister, #2 there are 2 lines from cannister, one running to air cleaner? and the other to pcv connection? And some where in the system there is a valve, check valve? that opens up to dump fumes from cannister into intake? Any and all help appreciated. Thanks
 

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Discussion Starter · #9 ·
Well, I went to junk yard today and got a cannister off an 83 chev. pu. I looked at quite a few, and some had quite a lot of connections. But some only had 3 connections. Which is what I bought. One connection is a tank vent another is a carb. vent, and the 3rd is a purge line. I noticd that some of these 3 connection cannisters but not all had a vent line? running behind cannister with a capped end that looks as though it moves with pressure or vaccum. I took this piece also , but not not sure how to incorporate into my 56 chev. with no venting at all. So ,today I drilled my gas filler neck and installed my vent line, and installed cannister in engine compartment by steering box. So tomorrow I will hook up my carb. vent to my air cleaner, and purge line to a vaccum port on carb. But, I wonder on my quadrajet carb. how to do this. I wonder if I should get a 2 connection pcv and run the purge line to it. Any help and comments appreciated. Thanks
 
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