Engine and Transmission Tech

I am almost finished my engine swap, a 2003 Gm 3400 V6 in my 1976 TR6. This engine has the stock EFI and I am using the stock TR6 gas tank. I am using a Walbro fuel pump mounted below the tank and I have run steel lines up to the engine. I used the existing nipple on the top of the tank for my return line. This nipple was originally for a vent line and a charcoal filter.
My question is about gas tank venting, is it necessary? Can I get by with a small hole in the rubber seal on the gas cap or will I have to take the tank out and get a bung soldered onto it for another line and a charcoal filter?

Thanks for your time and consideration!

Cheers
Byron

Byron

You may want to fab up a vent system. With EFI, the fuel in the tank can get much warmer then with carbs. This is because the fuel is constantly cycling through the fuel rail and returning back to the tank, which warms up the fuel and can create more fuel vapor. Additionally you have the constant fuel flow cycling which can create more vapor as well.

A charcoal filter system is best as the fuel vapors are burn't inside the engine and you don't have any fuel smell on hot days.

The second option would be to route the vent to an area on the car where the fuel vapors wouldn't be as noticable. Although you still may notice some vapor odor under the right conditions such as parked after city driving on a hot day.

With the gas cap vent you may notice fuel odor at the top of the car (TR6) on hot days.

On MGBs with a vented cap, on hot days, with extended periods of idling and a full tank, fuel can boil out the filler neck on to the paint work:-(

Bill



Edited 1 time(s). Last edit at 07/13/2013 12:01PM by MG four six eight.

Thanks Bill I guess I will bite the bullet and get a nipple soldered on to the tank and rig up a line and a carbon canister. "Sigh more work"

Cheers
Byron