957173 Volvo.Penta Gasket

5-1-1 Measurement of Compression Pressure
Compression pressure must be measured prior to disassembly of the engine.Measure the compression pressure at regular intervals and keep track of its changes. During the break-in period or after parts have been replaced with new ones, there is a slight increase in the pressure as the piston rings and valve seats fit snugly in position. As rough edges and friction between parts are gradually reduced, the pressure comes down.Measurement Procedure(1) Retighten the cylinder head bolts to specified torque and let the engine warm up until the coolant temperature reaches 75°C to 85°C. (2) Remove all injection nozzles or glow plugs from the cylinder head. To remove the glow plugs, use Socket Wrench (special tool). Cover the mounting holes and injection pipes to prevent entry of dust and dirt. (3) Install Compression Gauge Adaptor (special tool) on the injection nozzle or glow plug mounting hole together with a gasket and connect the compression gauge (measuring instrument).(4) Turn the engine with the starter and read the compression gauge pointer value with the specified engine speed. 1. Keep no fuel injected.2. Make sure that the enigne speed is also measured as compression pressure varies with the engine speed. 3. Make measurement for all cylinders, as wear and other conditions vary from one cylinder to another.(5) If the measurement is below the limit, disassemble and check.5-1-2 Cylinder Head and Valve Mechanism
(1) Removal and Installation For disassembly of parts with an encircled number, see following items.Removal Procedure(a) Where the push rod is forcing up the rocker, the rocker adjusting screw must be loosened before all cylinder head bolts are removed.(b) Loosen the cylinder head bolts in the reverse order of tightening.(c) Remove the rocker and bracket assembly and cylinder head assembly, raising them straight upward.(d) When removing the cylinder head gasket, use care to prevent scratches on the cylinder head and crankcase. (e) Removal of the tappet <D3> Remove the tappet, using Tappet Extractor (special tool). For removal, press the special tool until its O-ring is pressed tightly against each other and remove the tappet together with the special tool.Installation Procedure(a) Install the cylinder head assembly and rocker and bracket assembly to align the locating pins.(b) Tighten the cylinder head bolts in the sequence shown in illustration. Tighten step by step, and as a final step, tighten to specified torque. (2) Disassembly (a) Rocker and bracket assembly <Disassembly sequence>1 Set bolt <D3,4DR5>Set screw <6DR5>2 Retainer <6DR5>3 Rocker shaft bracket4 Rocker5 Rocker shaft spring6 Rocker shaft(b) Cylinder head assembly <Disassembly sequence> For disassembly of parts with an encircled number, see following items. 1) To remove the valve cotter, use Valve Lifter (special tool) and compress evenly the valve spring. 2) Whenever the valve stem seal or valve is removed, the valve stem seal must be replaced with a new one. 3) Remove the water director if corroded. 4) If cracks and fusion are evident on the chamber jet, insert a rod through the glow plug hole and tap it to drive out the chamber jet. (3) Inspection (a) Rocker and bracket assembly 1) Using the rocker I.D. and rocker shaft O.D., calculate the clearance. If the limit is exceeded, replace the bushing in the rocker. For replacement, use Rocker Bushing Puller (special tool). 1. Align the oil hole in the bushing with that in the rocker.2. Ensure that the bushing clinch is on the adjusting screw end.3. When press-fitting the bushing into rocker, start with the chamfered side on the rocker.(b) Cylinder head assembly 1) Inspection of valve spring Check the valve spring for squareness, free length, and proper tension, and replace if the limit is exceeded.2) Tappet to crankcase clearance <D3> If the clearance exceeds the limit, replace the tappet. 3) Measure the push rod runout. If the limit is exceeded, replace. 4) Cylinder head bottom surface distortion If the limit is exceeded, correct with a surface grinder.If the cylinder head height from top to bottom surface is below the limit, replace. 5) Measure the valve stem O.D. and, if the measurement is below the limit, replace. 6) Calculate the clearance with the valve guide I.D. and valve stem O.D. If the limit is exceeded, replace the valve guide.7) Replacement of valve guide For removal of the valve guide, use the Valve Guide Remover (special tool).To install, use Valve Guide Installer (special tool) and ensure that the special tool is positively seated on the cylinder head. The pressing force is specified for the valve guide, which must be reached by using the special tool.8) Inspection of valve Check the contacting condition of the valve seat and valve, after inspection and replacement of the valve guide.When the valve is pressed against the valve seat coated with red lead, make sure that the valve is not turned.9) Correction of valve face Grind the valve face with a valve refacer, the grinding dimension being limited to a minimum. 1. The valve seat angle is 45°.2. Correct to ensure that the valve margin is up to the limit.10) Correction of valve seat a) Grind with a valve seat cutter or valve seat grinder.b) After grinding, hold a #400 or similar sand paper between the cutter and valve seat and regrind lightly. 1. The valve seat angle is 45°.2. Correction must be made to ensure the valve seat width and valve sinkage are within the limit. c) Using a 15° or 75° cutter, correct the seat width to the nominal value.d) Seat the valve and valve seat. [See 12)]11) Replacement of valve seat The valve seat is cold fitted. Replacement procedure is given below.a) Grind the valve seat from inside to reduce the wall thickness. Then, remove it at normal temperature. b) Check if there is sufficient interference between the cylinder head and valve seat.c) Dip the valve seat into liquid nitrogen and let it cool down. But heat the cylinder head sufficiently.d) Using Caulking Tool Body and Caulking Ring (special tools), install the valve seat.