Graham Perry Posted January 8, 2006 Share Posted January 8, 2006 On the K series fuel tank where is the filler neck top vent pipe routed to ? I mean the one that starts at the top of the filler neck just above the moveable flap, not the wider one below the flap. Link to comment Share on other sites More sharing options...
Myles Posted January 8, 2006 Share Posted January 8, 2006 It vents to air. On hard LH corners with a more-than-half-full tank, you can see fuel p*ssing out of the car behind the RH wheel arch. There is a simple modification with a one-way valve and an extra length of pipe that stops this behaviour and still allows the venting to work. There are links in techtalk to a .pdf from the Graduates website that explains how to do it and also gives the Caterham part no. for the valve. You can get cheaper valves from DT etc. (not by much), but you might as well just follow the proven racing practice. Project Scope-Creep is live... Alcester Racing 7's Equipe - 🙆🏻™ Alcester-Racing-Sevens.com Link to comment Share on other sites More sharing options...
Graham Perry Posted January 8, 2006 Author Share Posted January 8, 2006 Myles, Thanks that is great. Now a related follow on question for someone to answer. Can someone confirm where the central vent pipe in the middle of the top of the fuel tank runs to ? Presumably somewhere higher than the top of the fuel tank neck ? I was initially tempted to join these two vents together but we did an experiment with a home made vacuum air pump and discovered that the tank wasn't venting at all like that when the fuel cap is on 😳 and all it did was suck the sides of the tank in 😳 Link to comment Share on other sites More sharing options...
Mark Durrant Posted January 8, 2006 Share Posted January 8, 2006 Graham The pdf is here. Mark D Comp Sec Link to comment Share on other sites More sharing options...
Mick Day Posted January 8, 2006 Share Posted January 8, 2006 Now a related follow on question for someone to answer. Can someone confirm where the central vent pipe in the middle of the top of the fuel tank runs to ? Presumably somewhere higher than the top of the fuel tank neck ? It runs to the filler neck, however I don't think it's necessary & I will be deleting it. Link to comment Share on other sites More sharing options...
julians Posted January 8, 2006 Share Posted January 8, 2006 My new fuel tank ( last month) didnt have a vent pipe on the top of the fuel tank. Link to comment Share on other sites More sharing options...
Frying Pan Posted January 8, 2006 Share Posted January 8, 2006 Previous thread here discussed this as well See some pictures of the build here. 8000 miles completed! Link to comment Share on other sites More sharing options...
Graham Perry Posted January 8, 2006 Author Share Posted January 8, 2006 Yes common sense says that is where the central tank pipe should go but I have run out of places to attach pipes to the neck 😬 I suspected a few challenges like this when converting from Carbs to injection. The main neck breather uses one of the small pipes per the PDF (thanks Mark ) and the thicker pipe on the other side of the filler pipe goes straight onto the fuel tank. There are no other places to connect the tank top breather pipe to. I guess this means I need to make one. Is this prolem a hangover from the charcoal vent system where one of these pipes ran forward into the engine bay ? I guess the other alternative is to blank off the tank top vent. Has anyone does this ? Edited by - Graham Perry on 8 Jan 2006 22:10:15 Link to comment Share on other sites More sharing options...
Mike Bees Posted January 9, 2006 Share Posted January 9, 2006 The top vent pipe on the neck, the one referred to in the Caterham document, would go the the charcoal cannister if fitted. I don't see any problem with blanking off the vent in the top of the tank, especially if the latest tanks don't have it. I can't remember if mine did or not... Mike Link to comment Share on other sites More sharing options...
Graham Perry Posted January 9, 2006 Author Share Posted January 9, 2006 Thanks Mike, sounds like another little ali welding session is called for to block it up 😬 Link to comment Share on other sites More sharing options...
CageyH Posted January 10, 2006 Share Posted January 10, 2006 I did this a while back, and joined my vent pipes with a T piece through a one way valve from Merlin motosport. Seemed easier than welding near the fuel tank 😳 Link to comment Share on other sites More sharing options...
Anthony Posted January 10, 2006 Share Posted January 10, 2006 Hi Graham, I put a k-series injection tank in, along with injection pipe between tank and filler cap. This has two connection points for the vent and central pick up point and might be a good reference point if you want to mod the existing carb neck Regards Anthony Link to comment Share on other sites More sharing options...
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