1942 - 1947 Chevrolet Shop Manual



	*6-7*

	necessary to replace the clutch housing, the new housing must be assembled to the block and checked before main bearings are installed. The housings furnished for service are selected and are interchangeable with the production part. Main Bearing Boring Machine This unit consists of the following parts, Fig. 10. A—Support Bracket and Clamps B—Universal Clamp Bolts C—Boring Bar Supports and Ball Bearings D—Boring Bar Centering Bushings E—Clutch Housing Centering Bushing F-Boring Bar G—Boring Bar Feed Support Bracket H-Feed Nut Yoke I—Feed Screw J—Turning Handle K—Boring Bar Cutters The operations for replacing main bearings are as follows: 1st—Support the Crankcase in the motor stand with bearing side of case up. 2nd—Remove old bearings and see that case is well cleaned. 3rd—Install centering bushings "D" in the front and rear bearing bores and install the bearing caps without shims. 4th—Thread the boring bar "F" through the bushings from the rear to the front. Then mount the dial gauge on the boring bar and check the alignment of the transmission pilot hole in the clutch housing, Fig. 11. The runout must not exceed .015". If it does, it will be necessary to replace the clutch housing before proceeding with the installation of the new main bearings.	5th—Remove the boring bar and the centering bushing from the rear bearing. Then install the clutch housing centering bushing "E" in the transmission pilot hole of the clutch housing. 6th—Install the boring bar through the rear centering bushing and thread the boring bar support bearings "C" over the bar, locating one support in the space between each two bearings. Be sure to push the boring bar through the front centering bushing beyond the reduced diameter portion. 7th—Install the boring bar support brackets "A" and line them up so there will be clearance between the bearing cap and support bracket for the installation and removal of cutters. Clamp the support brackets firmly to the oil pan rail of the cylinder block. 8th—Tighten the universal clamp bolts "B" on each support bracket evenly. As the bolts are being tightened, the boring bar should be turned by hand to make sure that it is free to turn without any indication of a bind. Remove the boring bar and the front centering bushing. 9th—Install the bearing shells in the cylinder block and caps. *NOTE—The front and front intermediate bearing shells are* very similar in appearance and it is possible to get them mixed. The front intermediate shells are identified by the letter "I" in the bottom of the oil groove. Should the intermediate bearing shell be installed in the front bearing bore, the sides of the bearing would be too high and would not permit the cap to seat firmly on the shims.** 10th—Place four .002" shims on each side of each bearing and install the caps. The intermediate bearing caps are marked "front" and "rear" for identification purposes. The front intermediate bearing cap is installed with the "FRONT" mark to the front of the engine and the rear intermediate bearing cap is installed with the "REAR" mark to the rear of the engine. The rear intermediate bearing shell is flanged because it takes the end thrust of the crankshaft. Tighten the bearing cap bolts evenly and make sure they are drawn down tight. 11th-Examine the boring bar to make sure the cutter scats are clean; then install the bar through the rear centering bushings and bearing supports. Examine the cutters to make sure they are clean and install them in the slots in the cutter bar. Cutters are lettered F-FC-RC-R to designate front, front center, rear center, and rear.

	Fig. 11— Checking Transmission Pilot Hole in Clutch Housing