273 overheating after new timing chain set and waterpump

Wally-T said
Hi again guys. I had a problem last fall with overheating so I installed a new thermostat and it ran nice and cool again, under half on the temp gauge even in hot weather in heavy traffic.
A couple of weeks ago I installed a new timing chain set, new manifold gaskets and a new water pump. Now it runs nice and cool on the highway and about half on the temp gauge in town but when I'm in traffic it moves 3/4 way up the gauge and would keep going if I didn't pop it into neutral and raise the rpm. I noticed that the old pump had a plastic impeller and the new one has a steel one. Does anyone know if the plastic impellers flow more water than the steel ones.
Thanks again for all your help folks, I'm gaining much knowledge here. Wally

There must be 2 threads on this... or the other I answered last nite at 11 pm and it was deleted.

I said you may have swapped a 8 blade for a 6 blade....that explains the traffic overheating. Typically a cooling system that is adequately sized will not boil over at idle with the radiator cap off...so you might gather that the cap is not responsible for the overheating in traffic....the cap issue would show up at speed, higher heat and pressure from the pump and growing temps its fighting along with the radiator.

Is or was it an 6 blade and ...what is the new pump 8 or 6?