I have a 1976 with 318. I have owned since 1980 and nothing has ever been done to the carburetor. The van has become hard to start after driving and the engine is hot. After a few days setting in the garage, I usually have to try 3 or 4 times before it fires up, but I think that is just the gas evaporating in the bowl. After driving when hot, after it starts up, I also get a smell of gas. The van runs good on the open road, other than it has lost a bit of power over the years. I might add I know nothing about the inner workings of a carb. An old-timer at the local garage told me it is probably a Carter carb, I know it is 2-barrel. He said the problem is probably the float is a fiber or plastic and has become saturated over the years. Could the timing be part of the problem. I also have the original fuel pump. Thinking about replacing that, I have 102,000 miles on the van.