I have a '73 240z. Whenever I fill my tank over about half full, gas leaks out badly. There are no known holes. I'm not quite sure where the gas is coming from, but it comes out quick when going down the road. What is my problem?

Have you checked the condition of your tank vent lines? These are the large fuel lines that run behind the tail light panel, through the floor and into the gas tank. Over time they get hard and brittle and crack. If so, then when you fill your tank over half full they will leak gas out of the tank. Particularly the long one on the driver's side of the car. It joins into the gas tank right at the tank seam.

I had the same kind of problem with my 240 when I bought it - couldn't put more than six gallons in the tank without gasoline running on the ground. The problem was the vent lines - replaced them and was able to top off the tank at anytime. As KMACK points out, the longer vent line taps in just above the tank seam. My experience is that it is the one to go first and also most often - mine is weeping now. You'll need to remove the inside rear panel and the inside passenger-side panel at the back of the car to get access. MSA has replacement lines.

The lines from MSA can get spendy. I would recommend getting a copy of the premiere issue of Sport Z magazine, as it had an excellent article on how to replace the vent lines using standard fuel hose. I believe I also posted a list of the hoses you would need on this board, they are available from NAPA.

Both EScanlon and myself gave a pretty good description of replaceing the lines for the vent tank. Follow this link: http://www.240z.org/forums/showthread.php?s=&threadid=1309

We've both been down this road before as have others. It's not too hard to do, but it does required dropping the tank a little.