Chapter 57 PowerPoint

Define these Technical Terms using the textbook:

1. block boring

2. crankshaft end play

3. cylinder honing

4. deck warpage

5. engine balancing

6. engine overhaul

7. piston ring gap

8. rear main oil seal

9. torque-to-yield specifications

Answer these discussion questions using the textbook:

1. How do you measure deck warpage?

Read the chapter summary below:

■ Inspect the cylinder block closely for problems before assembly. Magnafluxing is a quick way of finding cracks in cast iron blocks. Dye or fluorescent penetrant will find cracks in aluminum blocks. Cracked blocks can sometimes be repaired by welding, special epoxy, plugging, and sleeving.

■ Main bore alignment and deck warpage are checked with a straight edge and feeler gauge. Machining is needed to correct misalignment or warpage of the block.

■ Cylinder wear is best checked with a dial bore gauge. However, an inside micrometer or a telescoping gauge and outside micrometer can also be used. Check for cylinder out-of-round, taper, and diameter.

■ Cylinder honing is needed on used cylinders or cylinders that have been bored oversize. Honing produces the correct surface texture for proper ring break-in. Power honing will help remove cylinder taper and out-of-round. Flex or brush honing simply prepares the cylinder surface. A finer grit stone is needed when hard chrome or moly piston rings will be installed. Do not pull a spinning hone too far out of the cylinder or tool breakage can result.

■ A block should be bored when cylinder wear is beyond specifications. A machine shop can bore the block cylinders oversize. Then, oversize pistons must be installed. The overbore limit depends on the manufacturer check specifications. Cylinder sleeving can be done to repair a badly worn or damaged cylinder wall. The sleeve can be installed so that the same size piston will fit.

■ Always clean the block carefully after boring or honing. You must remove all grit so that it cannot circulate through the engine during operation. Use a pressure washer or hand wash the block with soap and water. Wipe the block down with an oil-soaked rag to remove the last of the grit.

■ Measure the crankshaft journals for wear. Check for general diameter, taper, and out-of-round. Also, check the crankshaft for cracks. If worn too much, have a machine shop grind the crankshaft journals undersize. Then, undersize bearings must be installed. Bearing undersize is usually stamped on the back of the bearing inserts.

■ Make sure you install the rear main oil seal correctly. The sealing lip must face inside the engine. Use the proper driver to install a one-piece rear seal to prevent seal damage.

■ Never oil the back of engine bearings. They should be installed clean and dry. Check oil hole alignment. Coat the bearing faces with heavy engine oil or assembly lube. Check bearing clearance with Plastigage. Torque main and rod bearing caps to specifications. Start out at about 1/2 torque and work up to full torque. Recheck final torque at least once. If the specification is torque-to-yield, turn each fastener the specified number of degrees past the torque specification.

■ Clean piston ring grooves of carbon with a ring groove cleaner or broken ring. Measure the piston diameter with an outside micrometer. Usually, measure just below the piston pin on the skirt. Piston wear is found by subtracting the measured diameter from the specification for diameter. Piston clearance is found by subtracting the piston diameter from the cylinder diameter. Clearance must not be too large or piston slap can result.

■ Measure piston pins and their connecting rod bores. Make sure the dimensions are within specifications. Replace parts or have the rods rebuilt if needed.

■ Check the piston ring gap by sliding the ring to the bottom of the cylinder bore with a piston. Then, use a feeler gauge to check the end gap. If the gap is too small, file the ring ends until within specifications, if allowed by the manufacturer.

■ Install the oil ring on the piston first. Make sure the expander-spacer ends butt together and do not overlap. Use your fingers or a ring expander to install the compression rings. Space the end gaps away from each other and slightly to one side of the piston pin ends.

■ Ring side clearance is checked between the compression ring and its groove. Slide the correct size feeler gauge in next to the ring. If the groove is too wide, replace the pistons.

■ Use a ring compressor to install the piston and rod into the block. Cover the rod bolts to protect the crankshaft. Then, tap the piston down into the block with a hammer handle. Torque rod and main cap bolts properly. Check rod side clearance with a feeler gauge.

■ Engine balancing may be needed if components are altered or changed. The reciprocating weight is the weight of the piston, rod, bearings, and oil. The counter weight on the crankshaft must balance this weight to prevent engine vibration.