I have used a super 2 core from mini spares on a 1330 for 4 or 5 years and it works great. Doesn't overheat idling in traffic but struggles to get to thermostat temp in winter (mostly due to the flow out of the heater takoff back to the rad top tank). The thing is, everything else is sorted. Ignition timing and mixtures are right (most important) and the cooling system is set up as follows - deep cast iron impellor water pump, large diameter pump pulley, yellow plastic fan, head heater takeoff run back to the top tank of the rad. This was all done at the same time but as others have said, I doubt there would be much difference if the 2 core was swapped for a good std mini rad.


Some useful info from one of Keith Calvers articles-

Water pumps. One good thing that came from 'S' development - an improved water pump! Unfortunately, the water pump has fallen into the oil pump syndrome - biggest is best! True for road cars spending most of their time at low-ish rpm under load, but not for high revving engines. The A-series pump is essentially centrifugal; it's pumping capability squaring with engine rpm. The design's such that maximum efficiency's around 2,000rpm, so at low speed it's hardly moving any water. At 2,000 rpm it's pumping all the water needed to cool the engine, so higher rpm just means it's sapping power. If your engine spends all it's time north of 3,500 rpm or so, a deep impeller pump is costing power, and may be causing cavitation, reducing cooling efficiency. To mediate the A-plus motors got a bigger diameter pump pulley (first seen on the Ss'), and should be used where possible on modified road engines.

cheers

Kevin