The Effects of Heat on Carbureted Engines

  For any performance or racing event that is long enough for fuel system components in the vehicle to absorb heat from the engine, the exhaust sysytem, and the hot air coming from a radiator, that heat can cause problems in the fuel system and in the engine's cooling system. Typical types of vehicles where these problems can occur include street vehicles,oval track cars, road race cars, off-road racing trucks, boats with enclosed engine compartments, and many others.

  The radiant heat of an engine and its exhaust system, and the heat in the air heated by going through a radiator, can be absorbed by fuel system components if they are not protected(insulated). These components can include carburetors,fuel lines, fuel pumps, fuel pressure regulators, fuel tanks, and fuel cells. As these componenets get hotter, they transmit heat to the fuel in them. As that fuel gets hotter, the fuel density(specific gravity) drops, and the air/fuel ratio gets leaner. This is because carburetors do not sense fuel temperature or compensate for changes in fuel temperature. 

  As fuel temperature increases and air/fuel ratios get leaner, the engine and the exhaust system usually generate even more heat. So, over time, the heating of the fuel and the heating of the engine can get into a vicious cycle where the temperatures of  both continue to climb, each causing the other to experience progressively higher tempratures as time goes on. The results of this vicious cycle can be increasingly sluggish engine performance, cooling system over-heating with fluid loss, and engine damage due to overheated oil and/or excessively lean air/fuel ratios.

  Insulating fuel system components can minimize the effects of , and even prevent, this vicious cycle of heating. This insulation must protect the fuel system components from radiant heat generated by the surfaces of the engine and the exhaust system, and from the hot air bathing around those components. To gain additional control over engine and fuel temperatures, reducing the heat transmitted into the air and to fuel system components by the exhaust system, by use of  materials like header wrap, can really help maintain reasonable engine and fuel temperatures. This, in turn, can help engine longevity and engine performance.        © Norm Schenck