New tique

pswann...the impeller is the rubber part!Well rubber and brass that is...
Get a new impeller and the O ring for the housing...Talk to Vince at Skidim so you get the right one...get a spare while your at it.

That thing is shreaded and has seen some serious heat. Try and flush the system most likely there are some small chucks of rubber from the impeller floating in the coolant jacket. Try and flush it out as best you can to avoid an over heating problem caused be blockage. remove the drain plugs on the back of the exhaust mainfolds, flush the lower hose to the circulation pump and the plugs in the block, one for each side. Use an air hose or water to flush it out and keep and eye on the temp gauge when you get it back on the water. Make sure you put the raw water pump back together correctly because you can get it backwards. If memory serves me right the set screw on the side of the pump needs to point towards the out side or away from the engine for the correct rotation of the pump.

double check for vaccum leaks around the carb and intake and maybe open up the idle mixture screws a little more. Check and re-adjust the timing and idle mixture screws until you get the idle down. With the high idle it can make the timing advanced some at idle. use a vaccum gauge to help adjust the carb if it's a holley. And don't assume that the dash tach is correct. if you have a newer style timing light use it for the rpm to double check the gauge.

You need the idle down to set the timing correctly otherwise you can have it over timed on the top end and have a ping problem. I would suggest leaving the motor box off the first couple of times you go out until you get the timing dial in. The box will muffle a ping and with it off it's easy to hear it. Good luck and keep us posted. Also check the timing at 3k it should be a little over 30 degrees don't get it over 35 degrees. Checking it at this rpm will let you know if the mecanical advance is working correctly.