I've got an old Chevy ('75) with a top-opening to the gas tank. The car has been sitting for 3 years without use. I want to clean the stale gas out of the tank. I have drained it as well as I can by disconnecting the fuel pump supply line. However, I'm sure there is a residual amount of gas in the tank. Under normal circumstances, I'd drop the gas tank, however, on this car, the former-owner tack-welded the exhaust pipes together which need to be disassembled to drop the tank. I don't want to have to cut out the exhaust pipes if I can avoid it.
My question is this, is there a safe way (solvent, etc) that could be used to get the stale gas out of the tank without dropping the tank?