Help needed with sb 318

exhaust- I was asking about your intake but those are not Strombergs
how old is your timing chain?
did your nylon gear slip a tooth?
post up a compression check
try some Champion LY suffix plugs or equivalent when you put your plugs back in inexpensive for testing and they do not miss
RC12LYC colder
RN13LYC
RFN14LY hotter start here
put a vacuum gauge on it and report
cheers
spray some carb cleaner around the base and on both sides of the throttle shafts and see if anything changes
do have a fire extinguisher handy
I also ran a 318 with no choke for years but when I went to snow country I put a manual pull choke on it