My 49 216 w/the notorious Rochester B carb hasn't had any problems w/87 octane E10 gas. Starts and runs nearly flawlessly w/no hesitation.....(knock on wood).
I've got approx. 9K miles on it since I rebuilt the carb & head.
Your crud is either coming from the fuel system (old gas tank is notorious for this) or your getting it in the gas.
Put a good late model inline fuel filter between the tank and fuel pump and a clear filter such as
this filter betwwen the fuel pump and carb and try the E10 again.
Good luck
Dave
