Chainsaw Repair

You are right,sme manufacturers curved the bottom edge of the intake port so the port didn't open suddenly with a huge "POP",with really affected idling and slow speed running,that sudden change of vacuum was hard to compensate the carb for. But todays carbs meter much better than the old Tillotson HL,the curved port edge is just paranoia left from the old days...
I always try to get maximim area from the the port in it's given duration,race bike engines never had a port floor like that.
Considering that an intake with 170 degrees of dur. at 13,000 rpm is only open for .00024 seconds(thats 24 thousanths of a second!) you must obtain all the area you can get.