A carburetor rebuilt in 1970 isn't going to last long on today's fuel regardless of ethanol content. You'll be rebuilding it sooner rather than later. Gaskets are probably dried out and brittle as is the accelerator pump.
The erratic idle is likely due to fuel leaking down the carb throat. Look down the throat while the engine idles and see if there is fuel dribbling on the throttle plate. When it conks out, see if there is a puddle of fuel sitting down on the intake manifold.
Test the accelerator pump by goosing the throttle with the engine off and looking down the throat. You should see squirts of fuel.
Your fuel pressure should be a 2-4 psi. Your current fuel pump may be too high pressure but I'd test it first.
Don't put too much faith in a new fuel pump unless it's an original pump that's been rebuilt. The new ones all come from China and are pretty much junk right off the shelf. (see some recent threads about multiple faulty new fuel pumps).
Last edited by Otto Skorzeny; 05/06/2023 3:06 AM.
