New Surplus Lycoming Carburetor Modification Kit p/n LW13761. O-320-E2D. We purchased these in an inventory. Mod Kit only applies to Marvel Shebler Carburetors p/n 10-5009 which have been installed on Cessna Model 172 Skyhawk. We believe that the affected serial numbers for the 172 and F172 are, 17263470, 17263492 thru 17263494, 17263497, 17263541 thru 17263558, 17263560 and on, F17201255 and on.