Heater core block off/valve
 

I was looking through the coolant flow diagram and noticed that all the flow through the heater core basically bypasses the radiator. Earlier in the year I had some temp issues at the track during the summer and have been thinking of things I may be able do to help it. Has anyone blocked off the heater core and noticed any significant drop on temps? If it made any difference it should be easy enough to add a ball valve in one of the heater lines to block it just during track days. Judging by the size of the lines I assume the flow is relatively high, so it seems like it should make a difference.
I don't ever have any issues on the street, and any track days I'm worried about temps the heater is irrelevant. I cant think of any downsides other than one other point of failure.

A little off the subject, but back when I had a Triumph TR4 which all had marginal cooling systems, I ran the heater on high with the top down on hot days or uphill pulls...this really helped keep the coolant temperature down to a tolerable level. Didn't keep MY temperature down, but that was an acceptable result.

Running the heater full blast is like adding a small extra radiator.

Also, IMO, blocking the coolant flow to the heater will not do very much for cooling, as long as the WP is creating enough flow to keep the coolant moving fast enough through the radiator. However, if you don't want to run the heater to help cooling, blocking the flow to it should help a little.

well it's 90+ during much of the driving season around here.. soo probably not turning the heater on as well. I'm mid project at the moment so even if i add a valve i wont know if its working because to many other changes at the same time. Just curious if its even worth dealing with, or if anyone else has tried. I suppose could change it between sessions the same day just to experiment.

But it is effectively taking hot water from the hottest half of the engine, then cycling it back into the engine without cooling first, so I feel like that would actually be worse than just loosing that much flow through the radiator.