Assembling Cylinder Head

Replace valve and valve spring assemblies using Valve Spring Compressor, Part No. 96600-36. Position valve keys so spaces between key halves are equal. Spaces between key halves must face front and rear of engine on intake valves.

Replace rocker arm assemblies making sure intake valve oiler is in place on intake rocker bearing, with oiler tube 3/32 in. from rocker arm. Rocker arms must be free or hydraulic lifters will not fill with oil.

Replace rocker arm cover and reinforcing ring. Use new cover gasket. Pull down cover reinforcing screws evenly to obtain tight seal.

Install new cylinder head to cylinder gasket and position rear head. Start cylinder head bolts. Turn engine until front cylinder exhaust tappet is Just starting upward. Install rear cylinder exhaust push rod and push rod cover. Make certain both push rod ends are properly seated in rocker arm and tappet.

Rotate engine until front cylinder intake tappet is just starting upward. Install rear cylinder intake push rod in same manner as exhaust push rod. Tighten head bolts evenly to insure a proper seal. First turn bolts snug, then using a torque wrench tighten each 1/4 turn at a time until all are drawn to 65 ft. lbs.

Repeat procedure to install front cylinder head.


Engine must be cold. Loosen tappet adjusting lock nut (1) and turn adjusting screw (2) upward, shortening push rod, until push rod has noticeable shake. Keep push rod from turning by holding with wrench on flats provided at base of push rod (3). Slowly turn push rod adjusting screw downward, lengthening rod, until all shake has been taken up. Mark adjusting screw with chalk and turn it downward exactly four full turns. Lock adjustment by tightening tappet adjusting lock nut. Always adjust tappets with push rod at its lowest position. Lowest position may be found by rotating engine until like tappet (intake or exhaust) in other cylinder is at highest point (valve fully open).

Install push rod cover spring cap retainers.

Always use new gasket at all joints unless otherwise specified. Clean off surfaces with a greaseless solvent (white gasoline is satisfactory) and install gaskets dry. Greased gaskets adhere to joint surfaces and become impossible to remove without damaging joint surfaces.

1. Lock nut

2. Adjusting screw

3. Push rod

1. Lock nut

2. Adjusting screw

3. Push rod

Figure 3B-5. Adjusting Tappets


Production engines with aluminum cylinder heads have always been supplied from the factory with steel intake valve guides, and with bronze exhaust valve guides starting in 1950. However, valve guides for parts order have been bronze for both intake and exhaust since 1950.

Because of recent changes, subsequently outlined, bronze valve guides will no longer be used for Big Twin OHV Models.

Exhaust Valve Guides

A change in exhaust valve guide material has been made, starting approximately February 1, 1957, in all Big Twin OHV engines. Valve guide material has been changed from bronze to a special steel alloy. This material is superior to the bronze alloy which it replaces, because of its greater resistance to wear at high temperatures.

The new steel exhaust valve guides will be supplied for parts order under the following part numbers:

18188-48A (Standard)

18189-48A (.001" oversize)

18190-48A (.002" oversize)

18191-48A (.003" oversize)

18192-48A (.004" oversize)

18193-48A (.006" oversize)

Steel Exhaust Valve Guide

Steel Exhaust Valve Guide

Above steel exhaust valve guides will be supplied henceforth on all orders received at the factory for the following replacement valve guides:

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