Crom Cruach Posted March 23, 2023 Share Posted March 23, 2023 I meant to ask about this unconnected line ages ago - should this line be connected to anything? Also I need to replace my fuel cap, should it be vented? How can I tell if my fuel tank is already vented? cheers. Quote Link to comment Share on other sites More sharing options...
Montemedic Posted March 23, 2023 Share Posted March 23, 2023 Paul, The 1970 fuel tank was non vented, just the gas cap is vented. The 71-72 tanks had additional bungs at the front corners of the tank and were vented externally. Depending on what year your Monte is, or what fuel tank is currently in your Monte now will tell you. Quote Link to comment Share on other sites More sharing options...
Crom Cruach Posted March 23, 2023 Author Share Posted March 23, 2023 It’s a 72 and the tank does have the side vents, so I think the cap should not be vented. Any ideas where this pipe should lead to? Quote Link to comment Share on other sites More sharing options...
stangeba Posted March 23, 2023 Share Posted March 23, 2023 From my 71 350 4BBL. One day I replaced the original rubber hoses and almost threw out this tiny blue restrictor stuffed inside of one of the hoses. The picture shows a small arrow inside of the top right hose, that's where the restrictor went. 1 Quote Link to comment Share on other sites More sharing options...
jft69z Posted March 23, 2023 Share Posted March 23, 2023 21 minutes ago, Crom Cruach said: It’s a 72 and the tank does have the side vents, so I think the cap should not be vented. Any ideas where this pipe should lead to? This is from a recent post, some diagrams of a '72 tank. https://www.firstgenmc.com/forums/index.php?/topic/27078-gas-overflow/#comment-250511 Quote Link to comment Share on other sites More sharing options...
420ponies Posted March 23, 2023 Share Posted March 23, 2023 That's weird, I don't have that line on my'72. I know that I have a non vented cap. Can't help you out Paul. Quote Link to comment Share on other sites More sharing options...
EVC Posted March 23, 2023 Share Posted March 23, 2023 Maybe this will Help…. "70's that were destined for sale in CA had the EEC system (Evaporative Emissions Control). Probably one of the better tank vent systems. The tank had 3 vents, a fuel/vapor separator near the tank, and a carbon canister under the hood that held vented gas fumes and burned it off when the engine was running." Quote Link to comment Share on other sites More sharing options...
EVC Posted March 23, 2023 Share Posted March 23, 2023 6 hours ago, Crom Cruach said: I meant to ask about this unconnected line ages ago - should this line be connected to anything? Also I need to replace my fuel cap, should it be vented? How can I tell if my fuel tank is already vented? cheers. Paul , That is the fuel return line … I'll send a photo of how mine is hooked up… Quote Link to comment Share on other sites More sharing options...
EVC Posted March 23, 2023 Share Posted March 23, 2023 Paul,,, The stock 3way fuel filters are difficult to find. I use the Wix fuel filter…..The fuel line to the left feeds excess fuel back to the tank thru that line.. It seems that some carbs, specially Edlebrock are sensitive to pressure and not all mechanical fuel pumps are consistent … Hope this helps…. Using that fuel return line solved a lot of problems for me. IMG_0219.heic Quote Link to comment Share on other sites More sharing options...
EVC Posted March 23, 2023 Share Posted March 23, 2023 . Quote Link to comment Share on other sites More sharing options...
Scott S. Posted March 23, 2023 Share Posted March 23, 2023 I remember seeing the "pressure relief" outlet on some fuel pumps (two clamp on spigots and one threaded) on engines using Q-jets that had the built in filter..... Not sure they make those versions of the pump anymore. But I think that might be where the "mystery hose" connected ? Quote Link to comment Share on other sites More sharing options...
EVC Posted March 23, 2023 Share Posted March 23, 2023 5 hours ago, Scott S. said: I remember seeing the "pressure relief" outlet on some fuel pumps (two clamp on spigots and one threaded) on engines using Q-jets that had the built in filter..... Not sure they make those versions of the pump anymore. But I think that might be where the "mystery hose" connected ? Scott,,,, Very possible …. As I recall both of my Monte's had "pressure/ bypass " style fuel filters… I think I still have one in my junk area…Many many years ago, on the advice of a mechanic, he recommended and installed a pressure regulator … It worked ok for awhile, but my milage seemed to drop significantly and the carb was always a problem…. I finally ditched the "pressure regulator" and found this dual outlet filter that would send excess fuel or "pressure " back to the tank…. I think the results are the same as the fuel pump you described… I think It's more of a volume thing than pressure… I know it works well. with my Edlebrock set up…. I think it was originally used to prevent vapor lock conditions…. I found it interesting that my daughters recently purchased 66 ElCamino , with a BB 454 has the Wix filter on it as well… Hers is mounted down by the fuel pump… Here is a link that may clarify some of the fuel cap issues… Ed Gas Caps- Vented or Non-Vented? | Team Chevelle.webloc Quote Link to comment Share on other sites More sharing options...
EVC Posted March 23, 2023 Share Posted March 23, 2023 Wix P/N 33040 on Amazon One of the reviews…. Reviewed in the United States on January 29, 2023 Verified Purchase I use this on an old car with a dedicated return line back to the tank. It does divert fuel back to the tank through a metered orifice. Solves problems such as vapor lock. Like I said I use it with a dedicated return line (1/4" line) Quote Link to comment Share on other sites More sharing options...
willie Posted March 24, 2023 Share Posted March 24, 2023 Ok Paul, The other guys have great info with the in line 3 way gas filter. My car is a 72 and it has a 454, i have and use the second line and that line that you are not using goes to the fuel pump. Your fuel pump doesn't have the extra feed, and that's where it goes. But do you have the charcoal canister on the other side mounted to the rad support? If you don't, look down by the frame under the power booster to see if you have another feed pipe coming from the gas tank as a vapor line, that hooks up to the charcoal canister. I would think your previous owner probably disconnected it. There is another post showing you how to hook up all the lines to the charcoal canister if you need that, and that's what you chose to do. 4 Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted March 24, 2023 Share Posted March 24, 2023 Hi Paul. To answer your original question, that is the return fuel line. Like Willie mentioned, the original pump had a return line along with the pump feed and the line to the carb, that was also mentioned. What was not mentioned is the fuel return line goes back into the tank by way of the fuel sending unit. 3 1 Quote Link to comment Share on other sites More sharing options...
Crom Cruach Posted March 24, 2023 Author Share Posted March 24, 2023 great info thanks again guys. I do have a charcoal canister behind the driver side headlight, I'll check it's connected to the tank. So with a Quadrajet, do you think I should be replacing my fuel pump with one that has the extra feed? The car is driving great, the only issue is slow response on wide open throttle - it bogs if I push the pedal hard, which I like to do, a lot. Quote Link to comment Share on other sites More sharing options...
EVC Posted March 24, 2023 Share Posted March 24, 2023 (edited) Paul … Matter of choice …… With the Quad , and if it's running well, I'd probably leave it alone. Putting a cap on the open line to prevent contamination would be a good idea.. Putting an extra fuel filter in line is never a bad idea though …. On my car,, with the Edlebrock , the three way filter seems to be the magic formula for my car … I see no reason that it wouldn't work well with the Quad….Hopefully your canister is hooked up …Use of it has more advantages than negatives… Just my opinion … Regarding the three way fuel pump, I'm not sure they make it any longer … There was a lot going on with the smog stuff in the late 60's and early 70's… Then of course there was Calif and their standards…. My 63 Bonneville ,W/Quad has a three way fuel filter that appears to be much like the one ,except for the bracket that was on my Monte…. Hopefully some other members can address the filter thing in-depth… Ed Edited March 24, 2023 by EVC clarify Quote Link to comment Share on other sites More sharing options...
EVC Posted March 24, 2023 Share Posted March 24, 2023 Regarding the bog on full throttle …. First thing I'd check is the accelerator pump….. Quote Link to comment Share on other sites More sharing options...
Scott S. Posted March 24, 2023 Share Posted March 24, 2023 22 hours ago, EVC said: Scott,,,, Very possible …. As I recall both of my Monte's had "pressure/ bypass " style fuel filters… I think I still have one in my junk area…Many many years ago, on the advice of a mechanic, he recommended and installed a pressure regulator … It worked ok for awhile, but my milage seemed to drop significantly and the carb was always a problem…. I finally ditched the "pressure regulator" and found this dual outlet filter that would send excess fuel or "pressure " back to the tank…. I think the results are the same as the fuel pump you described… I think It's more of a volume thing than pressure… I know it works well. with my Edlebrock set up…. I think it was originally used to prevent vapor lock conditions…. I found it interesting that my daughters recently purchased 66 ElCamino , with a BB 454 has the Wix filter on it as well… Hers is mounted down by the fuel pump… Here is a link that may clarify some of the fuel cap issues… Ed Gas Caps- Vented or Non-Vented? | Team Chevelle.webloc 125 B · 9 downloads Hi Ed, I've seen both, filter and pump, and imagine they probably work the same. Just a matter of plumbing. ;) Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted March 24, 2023 Share Posted March 24, 2023 6 hours ago, Crom Cruach said: great info thanks again guys. I do have a charcoal canister behind the driver side headlight, I'll check it's connected to the tank. So with a Quadrajet, do you think I should be replacing my fuel pump with one that has the extra feed? The car is driving great, the only issue is slow response on wide open throttle - it bogs if I push the pedal hard, which I like to do, a lot. Paul, the bog is most likely the secondary throttle plates (top) opening too quickly. The opening rate can be adjusted. 1 1 Quote Link to comment Share on other sites More sharing options...
Crom Cruach Posted June 7, 2023 Author Share Posted June 7, 2023 ok I finally have the wix 3 way filter on order. Does it need to be placed close to the carb? Do you keep the oem metal fuel line and add some hose to the end of it? What fittings would I need to interrupt the fuel line and connect the filter like this? tightened the secondary plate adjuster 3 quarter of a turn and wot bog is gone 2 Quote Link to comment Share on other sites More sharing options...
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