Engine Construction The 4.3L (262 CID) engine is a liquid-cooled 90 V6 type with overhead valves, cast-iron block, cylinder heads, and cast-iron balance shaft. Cylinder Block The cylinder block has 6 cylinders arranged in a “V” shape with 3 cylinders in each bank. Starting at the front of the engine, cylinders in the right bank are numbered 1-3-5 and cylinders in the left bank are numbered 2-4-6 (when viewed from the front of the engine). The firing order of the cylinders is 1-6-5-4- 3-2. The cylinders are encircled by coolant jackets. Cylinder Heads The cylinder heads have one intake and one exhaust valve for each cylinder.
A spark plug is located between the valves in the side of the cylinder head. The valve guides are integral and the rocker arms are retained on individual threaded studs. Crankshaft The crankshaft is supported by four crankshaft bearings. The number four bearing at the rear of the engine is the end thrust bearing. The bearings are retained by bearing caps that are machined with the block for proper alignment and clearances. Camshaft The camshaft is supported by four full round, sleeve- type bearings. A sprocket on the crankshaft drives a timing chain which in turn drives the camshaft through a sprocket.
Pistons and Connecting Rods The pistons are made of cast aluminum alloy using two compression rings and one oil control ring. Piston pins are offset 0.9 mm (0.0354 in.) toward the major thrust side (right side) to reduce piston slap as the connecting rod travels from one side of the piston to the other side after a stroke. The pins are a press fit in the connecting rod and a floating fit in the piston. Balance Shaft A cast-iron balance shaft is mounted in the crankcase above and in line with the camshaft. A camshaft gear drives the gear attached to the balance shaft. The front end of the balance shaft is supported by a ball-type bearing.
The rear end of the bearing uses a sleeve-type bearing. Valve Train The valve train is a ball pivot type. Motion is transmitted from the camshaft through the valve lifter and valve pushrod to the rocker arm. The valve rocker arm pivots on its ball and transmits the camshaft motion to the valve. The valve lifters with roller followers keep all parts of the valve train in constant contact. Each lifter acts as an automatic adjuster and maintains zero lash in the valve train and eliminates the need for periodic valve adjustment. Statement On Cleanliness And Care An engine is a combination of many machined, honed, polished, and lapped surfaces with very fine tolerances.
Whenever valve train components, cylinder head, cylinder, crankshaft, or connecting rod components are removed for service, they should be retained in order. At the time of installation, they should be installed in the same locations and with the same mating surfaces as when removed. Any time the air cleaner or TBI unit is removed, the intake opening must be covered. This will protect against the entrance of foreign material which could follow the intake passage into the cylinder and cause extensive damage when the engine is started. When any internal engine parts are serviced, care and cleanliness are important.
A liberal coating of engine oil should be applied to friction areas during assembly to protect and lubricate the surfaces on initial operation. Throughout this Section, it should be understood that proper cleaning and protection of machined surfaces and friction areas is part of the repair procedure. This is considered standard shop practice even if not specifically stated. G643 (E) Service Manual Chapter 3. Engine Mechanical System 45