Jeep Engines - Oljeep

4.7L POWER TECH V-8 345SECONDARYSECONDARY SECONDARY LEFTCAMSHAFTSPROCKETANDSECONDARYCHAINCHAIN GUIDETENSIONER ARMTWO PLATEDLINKS ON RIGHTAMSHAFT CHAINTWO PLATEDLINKS ON LEFTCAMSHAFT CHAINPRIMARY CHAINIDLER SPROCKETPRIMARY CHAINCRANKSHAFTTENSIONER SPROCKET 8ob3c710Figure 6 - 2The idler shaft is press fit into the cylinder block. A largewasher on the idler shaft bolt and the rear flange of the idlershaft are used to control sprocket thrust movement.Pressurized oil is routed through the center of the idler shaftto provide lubrication for the two bushings used in the idlersprocket assembly.There are two secondary drive chains, both are invertedtooth-type, one to drive the camshaft in each SOHCcylinder head. There are no shaft speed changes in thesecondary chain drive system. Each secondary chain drivesa 30 tooth cam sprocket directly from the a 30 toothsprocket on the idler sprocket assembly. A fixed chainguide and a hydraulic oil damped tensioner are used tomaintain tightness in each secondary chain system. Thehydraulic tensioners for the secondary chain systems arefed pressurized oil from oil reservoir pockets in the block.Each tensioner also has a mechanical ratchet system thatlimits chain slack if the tensioner piston bleeds down afterengine shut down. The tensioner arms and guides alsoutilize nylon wear faces for low friction and long wear. Thesecondary timing chains receive lubrication from a smallorifice in the tensioners. This orifice is protected fromclogging by a fine mesh screen which is located on the backof the hydraulic tensioners.PISTON AND CONNECTING ROD ASSEMBLY(Refer to Figure 6-3.)The pistons are made of a high strength aluminum alloywith an anodized top ring groove and crown. Piston skirtsare coated with a solid lubricant (Molykote) to reducefriction and provide scuff resistance. The connecting rodsare made of powdered metal, with a “fractured cap” design.A press-fit piston pin is used to attach the piston andconnecting rod.Note: DO NOT use a metal stamp to mark connecting rodsas damage may result; instead, use ink or a scratch awl.