Here's an interesting scenario for any of you running a Type 3 with any carb setup other than stock. I have recently fitted a set of DCNFs to a a 1641cc Type 3. Little bit of headwork, stock valves and a 110 cam. Pretty basic, but the motor ran hot and the fuel started to boil in the carbs. After ten minutes the car was undrivable. It took a while to work out just what was going on, but I got there in the end. You see the problem is that there is a lot of radiating heat in a Type 3 engine bay with a header type exhaust. VW new about the radiating heat with the stock exhaust so they pulled the air for the carbs from outside the engine bay.
Now when you fit aftermarket carbs the motor sucks in hot radiating air. The air goes in and out through the exhaust and kind of recycles. You start to get a compounding heat problem and before you know it the carbs can get so hot (as was my case) and the fuel actually boils!
We combatted this problem by mounting a heater fan from a Bay Window Bus with a Type 4 motor. You know the fan - it sits right there in the engine bay. It has a really good cfm.
Anyway, we mounted this fan to the left of the gearbox and then routed two ducts from the fan to the rear tinware. We cut two holes and fed the ducts straight to the carbs. One either side.
It worked an absolute treat - the carbs are now stone cold after a good thrash and the engine runs as cool as stock. Again folks, VW knew what they were doing. If you ever have any doubts, check out what the factory did and copy it as close as possible.