Improper valve adjustment (valves too tight) is a cause of pop back through the carb. If it is a solid lifter cam set intakes to no tighter than .006 and exhausts .016. Hydraulic lifters go 1 turn past zero lash.

Last edited by sstock; 10/21/2019 2:06 PM.

1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration