Welding on the balancer hub will probably ruin the rubber inserts in the damper. Use a speedy sleeve instead- - - -the same one that fits the small block V8 also works on a stovebolt balancer.
I just measured a 216 balancer with the hand crank lugs and a 5/8" belt groove and it measures 5 3/4" at the OD of the pulley sheave. That translates to an 18" circumference at the outside edge of the pulley sheave. Your 6 3/4" sheave will have a circumference of 21". That's a 16% increase in belt speed, which probably won't make a big difference in the speed of the water pump, which is already turning faster than the crankshaft even with the smaller pulley. A 1/2" belt, which is probably what your water pump needs to run, won't ride at the top of the 5/8" belt groove anyway, which will slow down the belt speed somewhat.
Jerry
Thanks for the info. I don't like speedy sleeves all that well.i have had them to wear though very fast in a industrial use. The equipment I am referring to was a slow speed gear box, but did run non stop.I know the engine is a much different application,and all though it will turn much faster, will only run short pieriods of time. I guess I was not to concearned about the rubber,thinking I could keep the heat to around 300 degrees at the rubber itself. Maybe that would be to hot for the rubber. I do have a 216 with a balancer on it. I never thought to measure it, but would have still wanted some advice.
