68 camaro, no AC.
Getting ready to get and put hoses on. Noticed that the nozzles coming out of the firewall were different sizes
5/8 and 3/4?

Which goes to the manifold/water pump?

Fittings still 1/2 inch on both the manifold and water pump?

Rick

yup. 5/8 and 3/4.

I forget which way is up, but they cross on the way to the engine. The lower on the firewall goes to the manifold, upper to the water pump

Is it the same for a '67?

Should be 5/8 on the mainforl and 3/4 on the pump. SBC

The high pressure, high temperature side will be the smaller of the two. this is done so the fluid exit does not deplete the fluid supply of the low pressure, low temperature side of the system. Same theory applies to the radiator: small hot exit , large cool supply.