After running the car for a bit, I hear a hissing noise. Pop the hood and realize that there is exhaust fumes squeezing out of the line where the rubber hose meets the hard line for the charcoal canister. I had replaced the line as the previous was dry rotted but it is not the right size right now (its non functional at the moment anyhow) and that's why it wasn't tight. But at any rate the tank was completely pressurized. I cracked open and removed the fuel cap and TONS of fumes released. I'm guessing this was all a result of the exhaust right below, but surely everyone else's can do this also? Is it even normal for the tank to pressurize that much? I know one day the car quite running and the pump sounded like it was cavitating. After leaving it sit for an hour or so it fired up and ran fine.

I can leave the cap cracked and it 'fixes' it but that doesn't do much good if I want to use the charcoal canister, which I do.

Thanks,
Ben

 

This is a design problem of the 3rd gen, the muffler being located below the fuel tank. If you put a lot of horsepower under the hood, you will put too much exhaust temperature under the fuel tank. My stock L98 would sit in the garage and "moan" after being run hard as the excess vapor would vent out the cap. Is that the 350 horsepower Ramjet 350? If so the only way to fix it is to put a heat barrier between the muffler and fuel tank or relocate the muffler. And we know there isn't many places under the 3rd gen to put a muffler and maintain ground clearance. See the exhaust forum for ideas. The charcoal canister will help but not enough. When the gas in the tank boils that is gas $$ that are being vented wherever they go out.
And congratulations again on having "adequate" horsepower under the hood of your 3rd gen. Sure is fun to drive though huh?

 

It's not THE 350hp ramjet, its MY 350/cam (basically same thing with better cam) with Ramjet intake, TPI ecm.

I guess I also just wanted to mainly see if this is a safety problem. I capped off the line going to the engine bay, I didn't think fumes around the headers were such a good idea. I'll have to find some solution for this though, I don't like leaving things unresolved.