Heater Return Hose

[march2022]

I just noticed on my recently acquired '79 B that the heater return hose runs to the rear of the cylinder head, as opposed to my '78 where it runs to the lower radiator hose. I checked my '78 head and there was a block off plate on the head. Any difference in cooling (or heating) depending how the heater hose is routed?
Christopher Chamberlain

[amgba]

The block-off plate on the cylinder head covers a hole in the cylinder head that provided water to the water choke on the Zenith Stromberg carburetor. Change the ZS carburetor to SU's or a Weber, or change the ZS water choke to manual control (using the excellent German built kit sold by Moss Motors), and the only option you have without changing the head to an earlier one is to use a block-off plate to cover the hole. I'm not certain that using the water choke hole to feed the heater system provides any tangible benefit(s) to the efficiency of the cooling or heating on a late model MGB.

Tony Thomas