beefman Posted February 8, 2021 Share Posted February 8, 2021 Morning folks. I have what may be a simple question that I wasn't sure how to look for in any of the manuals. What is the arm in the picture with the arrows pointing to it. Second part of the question is if I'm at minimum vacuum lines (read as no emissions/smog/anything other than what Gary lists in the vacuum systems tab) do I need it? My guess was it had to do with venting to the charcoal canister, but the pictures I saw only had a line fitting, not the push button with an arm. I only ask because it's a pain in the derriere to swap an accelerator pump with it while it's on the engine. If it's needed, I'll make do, if not, it'll get chunked. Thanks! Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 8, 2021 Share Posted February 8, 2021 I don't know, but I think that's a valve to open the bowl vent. You don't have anything connected to the bowl vent, so if you aren't using it you won't need that valve. I'm guessing that it is closed at idle and opens when you give some throttle. But that may be backwards. As for vacuum lines, have you looked at this page: Documentation/Underhood/Vacuum Systems? Link to comment Share on other sites More sharing options...
beefman Posted February 8, 2021 Author Share Posted February 8, 2021 I don't know, but I think that's a valve to open the bowl vent. You don't have anything connected to the bowl vent, so if you aren't using it you won't need that valve. I'm guessing that it is closed at idle and opens when you give some throttle. But that may be backwards. As for vacuum lines, have you looked at this page: Documentation/Underhood/Vacuum Systems? Thanks Gary. Yes, that's the page I was referencing in my post about only having those lines you listed hooked up. This is my first stop on the google machine when I'm working on Big Red. I appreciate the work you and everyone else has put into this site! Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 8, 2021 Share Posted February 8, 2021 It opens the external (fitting) bowl vent at idle, then closes it as you come off idle. Eliminating it will actually cause the carburetor to possibly run rich at cruise and definitely at WOT. Capping the fitting will eliminate that, but as someone else on here discovered, hot restarts due to gas fumes inside the air cleaner can make them a problem. Truck will run super rich for a bit until the fumes are purged. My personal recommendation is this: the evaporative system is a "neutral" emission device, it doesn't harm nor really affect the engine unless it is totally screwed up (GM has famous for the system on the feedback carbs having a valve that when it failed the engine would barely run). The system, unless it is completely removed (tanks vented to atmosphere) will simply keep you from smelling gas fumes even in a closed garage. Therefore, leave it in place and functional. Air pumps, EGR valves, Catalytic converters all can and do affect engine performance and if you do remove them keep in mind in some areas, it is against the law to remove or defeat them, your call on that. Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 8, 2021 Share Posted February 8, 2021 It opens the external (fitting) bowl vent at idle, then closes it as you come off idle. Eliminating it will actually cause the carburetor to possibly run rich at cruise and definitely at WOT. Capping the fitting will eliminate that, but as someone else on here discovered, hot restarts due to gas fumes inside the air cleaner can make them a problem. Truck will run super rich for a bit until the fumes are purged. My personal recommendation is this: the evaporative system is a "neutral" emission device, it doesn't harm nor really affect the engine unless it is totally screwed up (GM has famous for the system on the feedback carbs having a valve that when it failed the engine would barely run). The system, unless it is completely removed (tanks vented to atmosphere) will simply keep you from smelling gas fumes even in a closed garage. Therefore, leave it in place and functional. Air pumps, EGR valves, Catalytic converters all can and do affect engine performance and if you do remove them keep in mind in some areas, it is against the law to remove or defeat them, your call on that. Thanks, Bill. I obviously had it backwards. Link to comment Share on other sites More sharing options...
beefman Posted February 8, 2021 Author Share Posted February 8, 2021 It opens the external (fitting) bowl vent at idle, then closes it as you come off idle. Eliminating it will actually cause the carburetor to possibly run rich at cruise and definitely at WOT. Capping the fitting will eliminate that, but as someone else on here discovered, hot restarts due to gas fumes inside the air cleaner can make them a problem. Truck will run super rich for a bit until the fumes are purged. My personal recommendation is this: the evaporative system is a "neutral" emission device, it doesn't harm nor really affect the engine unless it is totally screwed up (GM has famous for the system on the feedback carbs having a valve that when it failed the engine would barely run). The system, unless it is completely removed (tanks vented to atmosphere) will simply keep you from smelling gas fumes even in a closed garage. Therefore, leave it in place and functional. Air pumps, EGR valves, Catalytic converters all can and do affect engine performance and if you do remove them keep in mind in some areas, it is against the law to remove or defeat them, your call on that. Thanks for the info. I have an open filter air cleaner on the truck right now. Would that make a difference in removing/capping it off? That's a pure curiosity question. As for the rest, grandpa removed a lot of it back in the 90's when he put the engine in the truck, I've been pulling the rest off the past few years as I tinker. I'm in a no emissions county in NC, and the truck is old enough now that no inspections at all are necessary once the truck reached 35 years old (84 model). I still appreciate the warning though. Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 8, 2021 Share Posted February 8, 2021 Thanks for the info. I have an open filter air cleaner on the truck right now. Would that make a difference in removing/capping it off? That's a pure curiosity question. As for the rest, grandpa removed a lot of it back in the 90's when he put the engine in the truck, I've been pulling the rest off the past few years as I tinker. I'm in a no emissions county in NC, and the truck is old enough now that no inspections at all are necessary once the truck reached 35 years old (84 model). I still appreciate the warning though. The gas fumes will still collect inside the air filter. You do need to cap the fitting as the valve will stay open without the linkage. Link to comment Share on other sites More sharing options...
beefman Posted February 8, 2021 Author Share Posted February 8, 2021 The gas fumes will still collect inside the air filter. You do need to cap the fitting as the valve will stay open without the linkage. Thanks. Curiosity satisfied. I'll leave the arm in place. Link to comment Share on other sites More sharing options...
85lebaront2 Posted February 8, 2021 Share Posted February 8, 2021 Thanks. Curiosity satisfied. I'll leave the arm in place. No problem, if you look at the "profile" link, you will see what I did for a few years. Link to comment Share on other sites More sharing options...
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