Hot Rods Does this tank need a vent?

I'm using this tank from Speedway on a speedster. Cap says "open slowly". Do I need to vent it or the line somehow before filling it full of gas and letting it set in the sun?

 

All fuel tanks need a vent or at some point you will not be able to pull fuel out of it.

 

Other than adding that the vent should have roll-over protection, that's all you need to know.

 

If the cap Say's vented..... It's vented, if not You need one

 

Okay, so educate me a bit please. I've been around a lot of old cars and tractors but this is the first time I've built something from scratch. Does it need to be vented from the neck, or can I put a T in the line below, but before a shut off valve, and run a line up to above the gas level?

 

You need to come up with a plan to replace the fuel in the tank with air as you use the fuel.

 

The vent needs to be at a high point of the tank that is not immersed in gas. A vented cap would be the easiest for this tank. If you T into the gas line going to the engine for the vent, it will push gas out of the vent line.

 

It is vented through the cap. It's what is called a "pressure/vacuum" cap. It prevents vapors from escaping the tank ( pressure) while allowing air in (vacuum) as fuel is used. That is the way all modern caps work. Pre 70's caps were just vented and allowed fuel vapors to just leave the tank. That was changed due to air quality issues.

 

Here's the bottom of the cap.

 

Does it say non vented? I would assume if it came with that tank, an there's no other provision... It's vented

 

It says, " Warning Remove slowly. Fuel spray may cause injury."

 

try sucking and/or blowing on that little hole in the center of the cap

 

Rarely a good idea to "assume" matters of health and safety.

 

Of course, we have all missed the obvious answer "CALL SPEEDWAY AND ASK THEM!"

 

I thought about that, but I have found that there customer service people sometimes know less about these things than I do.

 

Ding,ding,ding we have a winner.

Sometimes the obvious answer eludes us all. HRP

 

Speedway says it is vented.

 

EDIT: See picture in Post #9

I have used this style of fuel cap on several vehicles (both on-topic and OT) - it is designed to be used with vapor recovery systems. I found that the cap is one directional on the blow-suck test. The usual parts stores (NAPA, blister-pack-city, etc) did not stock original replacement caps.

I used a small drill bit to drill about 3 holes through the center disk. Go gently, the disks wants to spin in place. The cap will now pass the blow-suck test.

 

Question...with the holes you drilled, are you not vulnerable to a leak and possible fire in the event of a rollover accident? Not trying to be a smart ass here, just want you to be safe.

 

Put a vented cap on it. Done deal.

If you can't find one at the autoparts go the local Harley shop and buy a right side gas cap (early style) they are about 11 bucks.

 

So
you'll need a vent when you fill it- (air out)
You'll need a vent when you drive it (air in)
You'll need a vent when it gets hot
(Pressure and vapor out)

Pretty much any way you look at it is that you'll need a vent.

A vented cap certainly could work to cover it.

 

That style cap will allow air in but not out. That is why it has the pressure warning. It will keep fuel from leaking out when it expands from heat. That said, they can cause problems on early iron that uses less than 5psi of fuel pressure. The pressure build up can cause flooding if it gets high enough to push the needle off the seat. Using an old style vented cap can help prevent those problems. That is why fuel pumps in the 70's started having vapors return lines.

 

This happened to me! I used a vented cap and could not get the thing to stop drowning the motor. Ended up taking out one of the springs in the cap. Probably not the safest in a rollover, but with an RPU I'd probably be dead anyways.

 

One time when I was broke (common thing still actually) I needed a vented cap and had one that was not vented. Well I didn't have any money but I did have a drill and a tiny bit (like about 3/32 or 1/16) so I just drilled a hole in the center of the cap. I used that cap for a long time. LOL

 

So when did this fascination with roll-over valves begin?