The Viperhead dual glow was developed for the OS.91SZ. The Viperhead dual glow plug version is a high compression head which accomplishes 6 things: 1. Increases Power 2. Better Cooling 3. Improves Combustion 4. Smaller Size for ease of installation 5. Improves Sound 6. Eliminates unwanted dead engine autos Includes: 1 Viperhead 1 Head Shim .008 1 Head Shim .004 Directions: - When mounting your new Viperhead please note there is an offset in the shape. The longer portion of the head will go to the back of the engine allowing heat to transfer away from the engine. You will note that this places the angled plug towards the back of the engine as well. - This dual glow version will use (1 hot plug, A3, O.S. #8, or Enya3) and (1 cold plug, A5 or Enya 4~5). The hot plug goes in the angled position. We have used a very high grade of Aluminum that is very hard so please be sure to tighten the plugs securely. When using the dual glow version it is not necessary to light both plugs when starting as the second plug will light by the time you reach hover RPM.

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