I searched the FAQs and found similar threads, but not quite the same.

My 84 GS 12A carbureted vehicle can have a very heavy fuel smell in the inside while driving. I've had the car checked twice by a qualified mechanic (at least I believe he is qualified) but nothing turned up. There is no evidence of a leak - no liquid fuel anywhere that I can find, on or under the car. The weather stripping is pretty bad. It does not smoke excessively. It has a Holley 4bbl competition carburetor and an electric fuel pump. The MPG has dropped some recently. Any ideas? Tks.

 

Maybe exhaust leak somewhere , or carb running to rich , do you have a charcoal canister connected? , does it smell all the time? Does it smell just sometimes ?

 

As it is indicated the mileage has dropped suddenly, that means two things:

-fuel ending up outside the engine, from a leak

or

-fuel ending up inside the engine, being burned

Run the fuel pump for as long as necessary without running the engine to make SURE there isn't an external leak around the tank, lines, or carb.

If you are SURE there isn't a leak, then check the carb. Needle/seat may be damaged and hosing fuel into the engine. A rotary will run surprisingly well on 5x the amount of fuel it needs, but it will stink and both power & economy will suffer.