I would put the outlet hose (the one going back to the engine) on the top. That helps prevent air collecting in the top of the heater core. If that wasn't an issue, it wouldn't make a difference which way the flow goes.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.