ARMY TM 9-2815-253-24 AIR FORCE TO 38G1-93-2 MARINE CORPS TM 2815-24/3 NOTE The pistons with rings and connecting rods assembled, must be submerged in engine lubricating oil (MIL-L-2104)  just  before  installing  into  cylinder.    Drain  after  submersion  so  that  no  oil  is  left  in combustion chamber or inside the piston. x. Install pistons and connecting rods.  Refer to paragraph 3-30. y. Install oil pressure relief valve and oil strainer.  Refer to paragraph 3-21. z. Install crankcase door and dipstick.  Refer to paragraph 3-20. aa. Install pushrod rubber seals, washers, and pushrod tubes.  Refer to paragraph 3-27. ab. Install cylinder head.  Refer to paragraph 3-27. ac. Install pushrods and valve rockers.  Refer to paragraph 3-26. ad. Install cylinder head covers.  Refer to paragraph 3-25 ae. Install fuel injectors and fuel injector pipes.  Refer to paragraphs 3-17 and 3-18. af. Install water pump.  Refer to paragraph 3-10. ag. Install intake and exhaust manifolds.  Refer to paragraphs 3--6 and 3.-7. ah. Install fan.  Refer to end item maintenance manual. ai. Install battery charging alternator.  Refer to end item maintenance manual. aj. Install fan drive belt and tension it.  Refer to end item maintenance manual. ak. Install fuel filter and all other fuel pipes.  Refer to paragraphs 3-15 and 3-16. al. Service engine coolant, fuel, and lubrication systems.  Refer to end item maintenance manual and lubrication order. 3-5.  CRANKCASE VACUUM. 3-5.1.    General.    The  value  depends  to  some  extent  on  the  type  and  size  of  air  cleaner  installed  on  tie  engine. Regardless of type air cleaner used, vacuum with a clean air cleaner must not be less than a minimum of 0.79 in.  (20 mm) water gage (WG).  The vacuum is measured with a manometer at the lubricating oil dipstick hole with the engine running.  In engines in good condition vacuum increases slightly with engine speed but not proportionally.  A fluctuating vacuum may indicate faulty oil seals, valves, or piston blow-by troubles.  Crankcase pressure can cause serious oil leaks and often occurs in engines which need overhauling. 3-5.2.  Measure Vacuum. NOTE Average vacuum should be 1.37 in.  (34.8 mm) WG.  Minimum allowed is 0.79 in.  (20 mm) WG. a. Remove lubricating oil dipstick. b. If water manometer is available, connect one end of a 0.374 in.  (9.5 mm) OD plastic tube to a water manometer. Insert other end of tube into dipstick hole.  Refer to FIGURE 3-1. WARNING The noise level when operating could cause hearing damage.  Ear protection must be worn. c. Start engine and record reading on manometer. d. Stop engine, disconnect manometer and install oil dipstick. e. If water manometer is not available, place a piece of thick paper over the oil fill opening.  If crankcase vacuum retains paper, vacuum is good. 3-11