My 478 puts out a real strong smell when I start it up and run it

but everything else I own is has Catalytic Converters so you tend to get used to the newer cleaner running engines. When the 305 was in the 68 it did real well biannual California smog tests, I contribute a lot of that to the HEI ignition considering it had the Holley 500 which is pretty fat on the 305. Good thing the truck now is exempt from the smog tests.