The car I bought has 4-screw SU's and the '72-type intake manifold with ports for coolant to enter and exit. See thumbnails. I'm wondering if, for sure, all 4-screw SU's are earlier than the heated models. In other words, is there such a thing as a 4-screw SU with passages for the coolant. If my carbs lack those passages, is there any point at all to routing coolant into the manifold? The car might in fact run a little cooler if I simply closed off the ports--larger percentage of the total coo