4TNV98 & 4TNE98 Diesel Engine Section 3. Engine126Figure 6-123Inspection of Camshaft Bushing and Bores1. Measure the I.D. of the front bushing and theremaining bores in the cylinder block. SeeCamshaft on page 68 for specifications.2. If the camshaft bushing is not within specification,replace it using the appropriate service tool. If theremaining bores are not within specification, thecylinder block will require replacement as thereare no bearing inserts used.Inspection of Idler Gear and Shaft1. Measure the outside diameter (Figure 6-124, (1))of the idler gear shaft (Figure 6-124, (2)). SeeIdler Gear Shaft and Bushing on page 69 forspecifications.2. Measure the inside diameter (Figure 6-124, (3))of the idler gear bushing (Figure 6-124, (4)). SeeIdler Gear Shaft and Bushing on page 69 forspecifications.Figure 6-124Honing and BoringPistons must move freely in the cylinders whilemaintaining adequate compression and oil sealing.If the cylinder walls are scuffed, scored, out-of-round,or tapered beyond specifications, rebore and honeto restore cylinders to usable condition. Slightimperfections can be corrected by honing alone.1. Boring - Significant cylinder damage may becorrected by boring the cylinder to an oversizedimension. Refer to the appropriate parts catalogfor available oversize pistons and piston rings.• Boring a cylinder should always be done in aproperly equipped machine shop.• A bored cylinder should always be finished with ahone to properly prepare the cylinder surface sothe new piston rings will seat properly.• After the cylinder has been bored and honed,install the appropriate oversize pistons andpiston rings.2. Honing - Minor cylinder imperfections may becorrected by using a rigid cylinder hone (Figure 6-126, (1)). Be sure not to exceed the maximumcylinder bore specification.Deglazing - A used cylinder that did not requireboring or honing, should always be deglazed witha ball hone (Figure 6-126, (2)) before installingnew piston rings. This will properly prepare thecylinder surface to allow new piston rings to seatproperly.NOTE : When honing a cylinder, with either a ridgedhone or a ball hone (Figure 6-125, (1)), move therotating hone up and down in the cylinder bore toaccomplish a 30° to 40° crosshatch pattern (Figure6-125). This will provide the ideal surface for theproper seating of new piston rings.
