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Old 05-29-2004, 01:15 PM
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bbc,sbc main caps torque and thrsut bearing

hi to all. got a question for all the engine builders. how and what is the exact way to torque and set the main thrust bearing and main caps torque. I think everyone has a different way of doing it. Is the thrust bearing torqued last after the other mains caps are already done?What is the correct way of doing it? i seen guys start from the center out in a criss cross pattern. they would just torque the mains in a similar pattern to the heads? would there be any difference as far as any drag or tightness is concerned when rotating the crankshaft.

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Old 05-29-2004, 01:23 PM
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1. Tighten main cap bolts to approximately 10 to 15 ft.lbs. to seat the bearings, then loosen.

2. Tap main cap toward rear of engine with a soft faced hammer. Then retighten main cap bolts finger tight.

3. Using a bar, force the crankshaft as far forward in the block as possible to align the bearing rear thrust faces.

4. While holding the crankshaft forward, tighten main cap bolts to 10 to 15 ft.lbs.

5. Finish tightening the main cap bolts to specifications in two or three equal steps. This should align the bearing thrust faces with the crankshaft to maximize the amount of load bearing area in contact with the crank.
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Old 05-29-2004, 04:43 PM
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Really? I just torque all of the caps, then tap the crank forward and then back. Then I use a feeler gauge and measure the side clearance to each extreme, forward and back.
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The earlier sbc and bbc motors had dowel pins that did most of the thrust alignment. Since they went to one piece rear seals the thrust has to be more carefully set as there are no alignment pins on most of these blocks. I just tighten the thrust bearing caps to about 15-20 ft-lbs and smack the crank forward and back to set the thrust clearance. Then torque to specs.
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