VBelt pulley layout

Ben Ainsworth said

It's a 70-up (73 Duster and someone swapped in a 360, not sure when).
Part # on the waterpump is 2951571.
Pictures attached.

How free should this impeller spin when it's off the block? If I give it a finger twist it turns but stops almost immediately.

Thank you for help :)

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I’d replace that with a Milodon high flow unit. They are relatively inexpensive and way better than that. You should also buy a QUALITY high flow thermostat. Stewart Components has the best one IMO. Make sure the water pump is turning faster than the crank.

BTW, there is no reason to ever run a thermostat hotter than 190. A 180 is better. Running hot coolant temps is a mistake many guys make. When you do that, you have to reduce the compression ratio to keep out of detonation and that is a power loser.

Don’t know what intake manifold you are using but I’d block the heat crossover off if it already isn’t. That’s another compression dropping detonation maker.