My 422 smallblock build

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I used this washer which I ordered from Fastenal after measuring the rear flat tips of the impeller. I then cut it in half and flux core welded one half on and then the other onto the flats on the backside of the impeller. I then took a grinding point and cleaned all the welds up. My minimum clearance inside is around .040 or so where the inside of the pump has an irregular surface pattern. Water is pulled in through the center of the washer around the driveshaft and then thrown outward by the vanes (just like in an actual large scale pump, but just cruder). TIG welding it on after pulling the impeller out of the pump would really be the preferred way of doing it. But I’ve tested it on the engine with a belt looped over the Chuck of a drill and spare pulley bolted onto it. It really moves some coolant without a thermostat in the system and the bypass blocked. I’ll add a thermostat if I find out I need one but I’m more concerned with seeing if I can just get it to run cool with 10:1 on iron heads and a 22 inch two core copper and brass radiator, a clutch fan, and a good shroud.

re the thermostat. you'll often find an engine will run hotter without one, the reason being with no restriction (an open 'stat has a smaller hole than no 'stat) the water is allowed to flow faster. this might seem a good thing but the water 'needs' to be in the radiator long enough to transfer heat which if it flows too fast it can't get done. if you're still struggling with heat try a 'stat with the middle/guts cut out which will be a restriction to slow the flow.
neil.