Dave I just had a 318 2bbl & the crossover was not heating(should be able to put your finger on the crossover pasage & feel heat starting after several minutes) & I had opened up the carb(from hell) 4 times(not kidding) & it still wasn't right so I swapped to a streetmaster alum intake and an eddy 1406(w elec choke) & now starts excellent/runs fairly good after changing the metering rods one time. I left the clogged heat riser passages as is. imo Even though it looks nasty I would not mess with them(cant get anywhere near all of it out without taking off the heads to do it right & could loose pieces into the oil or the chambers with catastrophic results