Fuel filler / Rollover valve / etc ?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

yossarian19 · 03-12-2013, 12:21 AM

So, I'm going to be running an LS1 pump in a Mustang tank under my '59.
I see tanks listed as being with rollover valves, and I know they are factory equipment in most cars, but I have to ask: what is it for, and do I need one?

Also - modern filler pipes come with vent lines that run between the gas cap & tank in parallel with the filler tube itself. Is this just to let air purge out as you fill the tank, or is there some other purpose I need to keep in mind?

As it is, I have a return line & a pressure line w/ filter set up & the Mustang's 45 degree 1.5" or so filler neck. No other plumbing.
What's needed?

beanyard · 03-12-2013, 08:22 AM

I'd like to know too.

Posted via Mobile Device

Speedbumpauto · 03-12-2013, 10:04 AM

The filler neck on the Mustang tank should have a fitting for a 3/8 or so vent line that goes back to the tank. As you said, it allows air to purge when the tank is filled and with a vented cap, it allows air back in when fuel is used so a vacuum will not be created. If you can duplicate this, you don't need a rollover valve. I chose to use an aftermarket door/fill spout that had no provision for the vent to be covered by the cap so used the vent/rollover valve that came with the tank. Most newer systems use a closed system and a non vented cap in conjunction with a charcoal canister and electronic purge system to trap vapors and feed them to the engine on start up as well as vent the tank during operation. I think I posted pics of how I set up my system with the vent/rollover valve and fill door in the rear fender. Anyway, I have some if you need a look.

yossarian19 · 03-12-2013, 09:01 PM

The tank I bought has no provision for a vent pipe, it's just a plain 1.5" or so filler neck and the cam-lock for the Mustang sender.

I find an appropriate filler neck w/ internal vent pipe & run that, I suppose, with a vented cap.

Thinking about it, though - the cannister line on my Camaro fuel pump could be plumbed to a length of fuel hose connected to either a plain jane PCV valve or a small air filter, similar to what you'd see on a valve cover.... right?

03-12-2013, 12:21 AM	#1
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Fuel filler / Rollover valve / etc ?? So, I'm going to be running an LS1 pump in a Mustang tank under my '59. I see tanks listed as being with rollover valves, and I know they are factory equipment in most cars, but I have to ask: what is it for, and do I need one? Also - modern filler pipes come with vent lines that run between the gas cap & tank in parallel with the filler tube itself. Is this just to let air purge out as you fill the tank, or is there some other purpose I need to keep in mind? As it is, I have a return line & a pressure line w/ filter set up & the Mustang's 45 degree 1.5" or so filler neck. No other plumbing. What's needed?

03-12-2013, 08:22 AM	#2
beanyard Registered User Join Date: Mar 2011 Location: Idaho Falls, Idaho Posts: 247	Re: Fuel filler / Rollover valve / etc ?? I'd like to know too. Posted via Mobile Device __________________ 1959 Fleetside Big Window Long Box Standard Trim soon to be Deluxe 1953 GMC Carryall Suburban

03-12-2013, 10:04 AM	#3
Speedbumpauto Registered User Join Date: Aug 2011 Location: Tucson, AZ Posts: 917	Re: Fuel filler / Rollover valve / etc ?? The filler neck on the Mustang tank should have a fitting for a 3/8 or so vent line that goes back to the tank. As you said, it allows air to purge when the tank is filled and with a vented cap, it allows air back in when fuel is used so a vacuum will not be created. If you can duplicate this, you don't need a rollover valve. I chose to use an aftermarket door/fill spout that had no provision for the vent to be covered by the cap so used the vent/rollover valve that came with the tank. Most newer systems use a closed system and a non vented cap in conjunction with a charcoal canister and electronic purge system to trap vapors and feed them to the engine on start up as well as vent the tank during operation. I think I posted pics of how I set up my system with the vent/rollover valve and fill door in the rear fender. Anyway, I have some if you need a look.

03-12-2013, 09:01 PM	#4
yossarian19 Registered User Join Date: Sep 2011 Location: Nevada City, CA Posts: 908	Re: Fuel filler / Rollover valve / etc ?? The tank I bought has no provision for a vent pipe, it's just a plain 1.5" or so filler neck and the cam-lock for the Mustang sender. I find an appropriate filler neck w/ internal vent pipe & run that, I suppose, with a vented cap. Thinking about it, though - the cannister line on my Camaro fuel pump could be plumbed to a length of fuel hose connected to either a plain jane PCV valve or a small air filter, similar to what you'd see on a valve cover.... right?



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