My new Megadual exhaust for my buggy is coming in this week, and since I don't drive in weather below 60 degrees, I would like to remove the preheat tubes (single carb) coming from the intake manifold. What is the best way to do this? Are they welded in there, or can they be removed? Should I remove the manifold and have them cut off and try to plug them shut? They will look really bad all black and rusted with a shiny new exhaust hanging nearby. Thanks.
DON'T. You will regret it. Manifold and carb icing can happen in very warm climates, if engine produced vacuum and athmosphere humidity are high. Just believe it.
Sorry for the long answer, but I hope this would clear it up.
In a centermount carb application, you need heat for two reasons:
1) Prevent carb icing. When the engine is in operation, the evaporation of fuel in the carb absorbs heat, so the carb gets cold. If the temperature of the inhaled air is not high enough or there isn't a heat source to provide the heat absorbed by the evaporated fuel, the carb will get very cold and ice will deposit inside and outside the carb. First, the idle circuit which has smaller passages will be blocked, then (in very cold weather) the main circuit of the carb will be affected too. The solution is either to heat the carb from the manifold flange (case of dual carbs), or direct preheated air in the air filter (as VW did and most other automotive manufacturers did in their carbureted engines).
2) Heat the long intake manifold to keep the fuel atomized. In a centermount configuration, the fuel charge has to travel a long distance from the carb to the heads. If the intake manifold is cold, fuel condensates on the walls, so a leaner fuel charge reaches the combustion chamber. Heating the intake manifold reduces this phenomenon. However, you should not heat the intake charge too much cause this leads to power loss and detonation. VWs solution to this was to mate the inlet manifold center section with a smaller tube in which hot exhaust gas flows. The area of contact is not very large, so that the manifold doesn't overheat durring the summer months. It's purpose is to heat the manifold, not the carb. VW directed preheated air to the air filter to heat the carb.
Given these facts, you can figure out that there is an outside temperature over which the intake system can operate without preheat. In my experience based on a stock carb configuration, you can get away without preheat, is outside temperature is above 85 degrees. Bellow that, you need at least the carb preheat.
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