This Willys Motors publication lists specifications and service standards for their 1952-54 vehicles, including acceptable tolerances for a number of the specifications.
The Foreward says, "The tolerances are, in general, manufacturing tolerances, rather than wear limits.
"These tolerances are provided primarily to guide those who overhaul and rebuild engines, engine accessories and other units. Only by the careful fitting and adjusting of parts to factory tolerances can top performance be assured from rebuilt units.
"Wear tolerances are largely a matter of the good judgement of a skilled and experienced mechanic. The amount of wear permissible before parts are replaced is determined in large degree by the amount of economical service that can be reasonably expected as compared with the cost of restoring ideal 'new car' fits and performance."
Page 8 -- Four Cylinder L-head and F-head Engine Standards: General Specs, Pistons, Piston Rings:
Page 9 -- Connecting Rods, Piston Pins and Bearings, Crankshaft, Camshaft:
Page 10 -- Valves, Springs and Tappets, Oil Pump:
"Important Note: Specifications in this publication are for standard sizes and this must be considered working with udersize or oversize replacement parts. Engines fitted with undersize or oversize parts by the factory are identified by letters used with the engine number in accordance with the following:
"Letter 'A' denotes......... .010 Undersize Main and Connecting Rod Bearings
"Letter 'B' denotes......... .010 Oversize Pistons
"Letter 'AB' denotes........ Combination of 'A' and 'B'."
Note also: The connecting rod weight of 40 oz. given in these specs is apparently correct for some military and industrial versions of the F-head engine. The figure of 32 oz. in the Service Manual specs is more common, and is much closer to the 31 oz. weight measured recently by Eric Lawson.
Thanks to Tom Griesser for scanning this publication. -- Derek Redmond
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