Rear intake coolant bypass

Just a thought on a simple test:
Get a precise temp measuring device in the engine, and run it up to temp with the bypass in place with some significant loading. Then pinch the hoses closed and try it again under the exact same loading conditions and see if there is any difference. That is an easy test, and at least a first order check on things; takes some care to make the before and after conditions the same.

And I really don't know if there is an issue..... just sayin' that the flow paths are changing and that could effect how the system cools various part. Keeping hots spots from forming in the heads is an important matter (for detonation when things are being pushed hard). It is hard (for me at least) to imagine that this setup does not reduce flow in the heads at least a bit. But it might be such a small change as to make insufficient difference in head temps that have any real impacts.