The Stovebolt Site Forums The Parking Lot Big Bolts About at my wits end, getting an engine to run

Sooty plugs says rich, but it's hard to argue with a carb. swap not changing conditions, unless the "old Chevy" carb had the same issue. I think the '50s 235s used a Rochester carb with a vacuum port in the manifold - is this there and open?

Popping and backfiring sounds like timing. I agree, test the vacuum advance (I got a Mighty-vac kit at parts store, very useful and not that expensive).

Can you swap out the coil and the condenser also to rule these out?

Does it consistently idle ok? Just faulters at mid or higher rpm?

-Michael