70 Expansion Tank

[Jeff A.]

My 70 small block has a plastic coolant expansion/ocerflow tank that I'd like to replace with a vintage metal tank. There are two large hose connections on the bottom and two smaller ones on the top near the fill hole. What goes to each of these connections. Thanks

[Joe L.]

Re: 70 Expansion Tank

Jeff-----

I have no idea where a plastic supply tank could have come from on your car. GM never used a plastic supply tank on ANY C2 or C3 Corvette, although 73 and later do have plastic coolant recovery tanks.

Anyway, on the original type aluminum tank, there are 2 3/4" hose connections on the bottom of the tank and these go in the 3/4" (lower) heater hose circuit. The "forward" one connects via heater hose to the water pump heater hose nipple. The "rear" connects via heater hose to the heater core.

The 3/8" tube welded to the top poetion of the tank connects via 3/8" ID hose to the similar fitting on the top, right side of the radiator. The other 3/8" fitting (the one just below the filler opening on the tank) is for the overflow hose.