MACK MP8 EURO 4 ENGINE DESIGN FEATURES [200 EA] Main features of the cylinder head are: One-piece cast iron Integral thermostat housing 3 Separate chambers for exhaust and inlet at each cylinder make this a “crossflow” design. The fuel channel, drilled from front to rear, connects with grooves machined around each injector opening. A plug at the rear of the cylinder head seals this channel. CAMSHAFT AND VALVE TRAIN The engine has an overhead camshaft and rocker arm shaft in support of four valves per cylinder. The camshaft rides on seven journals with a bearing cap and support block (saddle) at each point. The bearing inserts (shells), bearing caps and support blocks are replaceable.
In standard configuration (with VGT exhaust brake only), there are three cams for each cylinder, including inlet, injection and exhaust. There are four cams per cylinder in the optional configuration (VGT exhaust brake plus PowerLeash™) with the addition of a “brake” cam at each cylinder. Figure 3 — MACK MP8 Euro 4 Engine — Conventional Chassis To accommodate the low cab forward design, the EGR system and the inlet manifold are configured differently than for the conventional chassis. The EGR mixer mounts at the front of the inlet manifold on the conventional chassis, but near the rear of the manifold on the low cab forward design.
The rocker arms are positioned on the shaft (front to back) in the order of inlet, injector, exhaust and brake, if so equipped. Both the inlet and exhaust rocker arms each drive the valve pairs via a pinless yoke (bridge). On engines equipped with PowerLeash™, the “brake” rocker arm works in combination with the exhaust rocker arm to precisely control the opening and closing of the exhaust valves for engine braking. Engine Components CYLINDER HEAD 4 Figure 4 — Cylinder Head with Valves and Camshaft Supports Page 16 DESCRIPTION AND OPERATION