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sevisehda The other day I had the idea of getting 2 heatcores, cutting off the bottoms then soldering them together end-to-end. Then place the now 16" x 8" rad at the bottom of my case. Theoretically it should have the resistance equal to that of the orginal setup just with better cooling. With the 4 fittings it would be very easy to do a 2 pump setup.
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Interesting idea, certainly I think it would work better than trying to do a double thickness core.
However depending on how you plumbed it, you might or might not have the same resistance as a single core.
(Note, all flow resistance discussion relates to water flow - airflow resistance would be unchanged for any given part of the core, but the total airflow resistance would drop simply because of the increased rad surface area, just as if two cores were used next to each other)
(Second note - DP = dual pass core, SP = Single pass core, and all comparisons are based on using the same base core number (doesn't matter what it is) for all scenarios)
There is considerable flow resistance from the tubes themselves, so unless you plumbed the thing in such a way that the effective tube length and number of tubes remained the same, then the resistance would go up.
Let me think about the picture for a moment
I am assuming that you are using DP cores since you mention ending up with 4 I/O connections. In effect you would have created two parallel SP rads in the same body, each having a number of tubes equal to one pass in the DP core, and twice the DP core length. Assuming that both passes had the same # of tubes (not always the case) then:
1. If you ran two seperate loops, the flow resistance would be about the same as if you had a seperate DP core on each loop.
2. If you had a single loop, and 'Y'ed the flow so that each pass got about half the coolant then the flow resistance would be lower, approx what you would get by running two DP cores in parallel. (or one SP core of the same size as the combined unit)
3. If you used a loop of tube to tie the output of the first pass to the input of the second (effectively creating a bigger DP core) then the coolant flow resistance would go UP due to the increased tube length, approximating what you would get with two DP cores run in series.
I can't think of any other plumbing setup scenarios.
Aside from the 'coolness' factor from doing something unusual
and possibly reducing the total size by the length of two tanks (approx 1.5" on average) I don't see ANY advantage that your proposed setup would offer over doing the same thing with two cores not soldered together.
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From a structural standpoint, I think you would also have problems. I will admit my exposure to the innards of heater cores was brief and many years ago, but my recollection is that core construction would make your idea difficult to do.
A typical core is made from a bunch of ribbons of brass that are formed, pressed together, and soldered along their edges to form the tubes. (more ribbons go in between the tubes to make the cross fins) The ribbons are folded back and forth such that the folds define the tank-tank length of the core. The tanks are soldered around the perimeter of this folded area, and don't actually touch the tubes themselves. While the core-tank mating surface of the folded area is kept very flat, the tube openings are irregular and not consistent in their relationship to the mating surface.
I suspect rather strongly that you would find it very difficult to fasten the two core lengths together unless you created some sort of 'adapter tank' with a mating surface on each end to match the two oore mating surfaces. There are a couple ways I could see of doing this, but I don't see an easy approach that would be worth the effort. I also suspect that the soldering would be a bear as well since you would have to figure out how to make two joints in close proximity without having making the second joint melting the first joint (or the core)
I don't know just what such an 'adapter tank' would do to the flow resistance, I suspect nothing good.
As a first guess, I would expect it to be approximately equal to the impact of the bottom crossover tank on a DP core, which again would suggest that there is little gain from what you propose.
I suspect that if you actually needed that much cooling, and wanted low flow resistance the best way to achieve it would be to run two SP cores with no attempt to connect them except with plumbing. (If both would be used in the same loop, run them in parallel rather than series.)
Gooserider