"Theres THREE versions ! ? !* maybe . Threaded for ' jetstream ' muffler back in the port , undrilled and unthreaded ditto ,
and long un etc'd THINGS there , going most of the way out , can drill'n tap em all , of course . But Not right thru, please ."
What happens if you drill them clear through? It appears that the drill will hit some fins, and quite possibly break the drill. Clearing the fins away with a Dremel would fix that. Would a clearance hole for a 4-40 or 3mm screw break through into the cylinder bore in the case, bypass, or something vital? I have a few of these in parts, collected cheap at swap meets, in R/C form, a B.Gardner ABC P&L/Rod/wristpin set, and a project in mind for one.
Steve