126 Auto Engine Repair Copyright by Goodheart-Willcox Co., Inc. 2 4 3 2 3 4 1 2 3 4 Firing order Cylinder numbers Timing marks 20 16 12 8 4 0 4 2 4 6 Firing order 1 6 5 4 3 2 3 5 20 16 12 8 4 0 15 3 2 4 5 6 8 4 3 6 5 7 2 2 4 6 8 Firing order 1 8 4 3 6 5 7 2 7 5 3 24 20 16 12 8 4 0 5 3 6 2 4 2 3 4 5 6 Firing order 1 5 3 6 2 4 Crankshaft balancer Distributor cap or coil pack numbers Figure 6-2. Numbers usually run in sequence, from front to rear, on inline engines. Cylinder numbers vary with V-type engines. Note how you can determine the number one cylinder on V-type engines. It is slightly ahead of the front cylinder on the opposite bank. (Mitchell Manuals) Two rods per journal One rod per journal V-Type Crankshaft Inline Crankshaft Figure 6-3. A V-type crankshaft has two connecting rods per rod journal. This is why the number one cylinder on a V-type engine is ahead of the front cylinder in the opposite bank. Note how an inline engine only has one rod per journal. • A V-type crankshaft has two connecting rods bolted to the same journal, Figure 6-3. The journal may be splayed or, more commonly, not splayed. A splayed crankshaft has the individual rod journals on the same crankshaft journal machined off-center. The splayed rod journal has an inherent weakness because the crankshaft pins can break under high load or engine speed conditions. • A cast iron crankshaft is made by pouring molten iron into a mold. It is a common type for light- and medium- duty applications. • A forged steel crankshaft is made by hammering hot steel into a mold using tons of force. It is much stronger and more rigid than a cast iron crankshaft and is used in high-performance applications. • An internally balanced crankshaft uses the counter- weights on the crankshaft to offset the weight of the rod and piston assemblies. Metal is added to or removed from the counterweights to balance the engine and prevent vibration. • An externally balanced crankshaft uses internal coun- terweights, but also has weights on the flywheel and a Before AFT Before 8 4 0 2