RESTORING HISTORY ONE CAR AT A TIME

Engine

Oil Grooves in Main Bearings

After rebabbitting a cylinder block be sure to form oil grooves in the main bearings. (See Fig. 1226.) K. R. Wilson furnishes a tool for this purpose.

OVERHEATING

Should you encounter Model “A” cars or “AA” trucks that are overheating, always check the radiator splash plate to make certain it has been changed in accordance with instructions given on page 450 in the April 1930 Service Bulletin, also check the timing. Should the water in a radiator be allowed to get very low, …

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CLEARANCES AND LIMITS USED IN ASSEMBLY OF MODEL “A” ENGINES

Size of Parts Diameter of pistons …………….. 3.8745 Diameter of cylinder bore ……….. 3.876 Diameter of crankshaft main bearings .1.624 Diameter of crankshaft pin bearings .. 1.499 Diameter of camshaft bearings ……. 1.560 Shims .002 thick are placed between all main and connecting rod bearings after burnishing. This is for oil clearance. Clearances Piston clearance …

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LOWERED OIL CONSUMPTION

Several improvements have recently been made in Model A engines which tends to still further lessen oil consumption. A shield is now provided which fits around the oil pump and insures a more uniform distribution of oil to all cylinders. The oil pan tray has also been lowered 1⁄8”· This has been accomplished by correspondingly …

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SIZE OF OIL PASSAGE HOLE IN PISTON INCREASED

To facilitate the flow of oil the size of the oil passage holes in the piston in the lower ring groove has been changed from .100 to .125″. (See Fig. 1172.) The width of the milled slot in the oil control ring was also increased.

MARKINGS ON PISTONS

To eliminate any possibility of pistons be- ing incorrectly assembled in an engine, the word “front” has been placed beside the arrow, that is, stamped on top of the piston. When the piston is correctly assembled in the engine, the arrow will point toward the front of the car (see Fig. 1121) and the split …

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NEW EXHAUST VALVES

New special alloy cast valves A-6505-A2 are now being used in production in all engines for exhaust valves only. The regular valve A-6505-Al is used for the intake valves. The A-6505-A2 valves are available for service when it is necessary to replace an exhaust valve. The A-6505-Al’s should be used for the intakes. The A-6505-A2 …

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Design of Engine Figures Changed

To lessen any possibility of outside individuals attempting to change engine numbers, the figures 1, 6, and 9 have been changed. (See Fig. 1118). Dealers should immediately provide themselves with a new figure one, six, and nine.

VALVE SPRING DESIGN CHANGED

A-6513-Al valve spring has been obsoleted. The new valve spring A-6513-A2 can be easily distinguished from the old design as the free length of the new spring is 2 15/16”; the free length of the old spring is 3” 7/16. In addition the new spring has 11 left hand coils whereas the old spring had …

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.005 O.S. PISTON RINGS

The following oversize piston rings have been released for service. These are in addition to the .010, .020 and .030″ oversize piston rings that have been available for some time. A-6150-BR piston ring .005″ oversize, 1⁄8” wide. A-6152-BR piston oil control ring .005″ oversize, 1⁄8”wide. A-6153-BR piston oil control ring .005″ oversize, 5/32” wide.

REMOVING CARBON

Carbon must be removed from piston heads with a carbon scraper. Never use a wire brush, as particles of carbon or a strand of wire from the brush are liable to be forced between piston and cylinder wall with possibilities of scoring. Before replacing cylinder head pour at least a tablespoon of engine oil around …

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Pistons

To assure maximum lubrication of the piston pins, a 5/32“ oil hole is now drilled through both piston pin bosses. (See Fig. 901.) In addition, the diameter of the pis- tons has been increased .001″. In production, new pistons are now fitted to cylinders with a clearance of from .0005 to .0025. In service, if …

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