Basic modifications for newbies
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'''There are numerous sources of information to assist the untrained individual in the rebuilding or repairing of specific components of a vehicle, but there needs to be a place where he/she can learn what to do and what not to do in the modification of their vehicle(s). This article will attempt to fill in the blank spaces in their understanding concerning these modifications. | '''There are numerous sources of information to assist the untrained individual in the rebuilding or repairing of specific components of a vehicle, but there needs to be a place where he/she can learn what to do and what not to do in the modification of their vehicle(s). This article will attempt to fill in the blank spaces in their understanding concerning these modifications. | ||
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*11. Failure to clearance lifters in their bores so that they spin freely. Lifter clearance should be 0.0012" to 0.002", with 0.0015" (one and one/half thousandths) considered close to ideal. Too loose is as bad as too tight. | *11. Failure to clearance lifters in their bores so that they spin freely. Lifter clearance should be 0.0012" to 0.002", with 0.0015" (one and one/half thousandths) considered close to ideal. Too loose is as bad as too tight. | ||
| − | *12. Failure to initially adjust the valves properly. Using the "spin the pushrod until it feels tight" method will normally result in valves too tight. | + | *12. Failure to initially adjust the valves properly. Using the "spin the pushrod until it feels tight" method will normally result in valves too tight. With both valves closed and the piston at TDC on the compression/firing stroke for that cylinder, hold the tip of one rocker arm down tightly against the valve stem with one hand and jiggle the pushrod up and down with the thumb/forefinger of your other hand until all play is removed, then turn the rocker nut 1/2 to 3/4 turn to set the preload. Now, do the same thing on the other rocker arm/pushrod for that cylinder. The bulletproof way to adjust valves is this method just described. Beginning on the #1 cylinder and following the firing order, you can adjust the intake and exhaust rockers for each cylinder as you turn the crank 1/4 turn at a time. In other words, on a Chevy, bring the piston of #1 cylinder (front, driver's side) up to top dead center on the compression/firing stroke. Both valves will be closed and the intake and exhaust lifters will be on the heel of the camshaft at that point, so you can adjust both the intake and exhaust rockers for that particular cylinder at the same time. Turn the crankshaft 1/4 turn clockwise and adjust the intake and exhaust rockers on #8 cylinder (rear, passenger side). It is the next cylinder in the firing order after #1. After you have adjusted both the intake and exhaust rockers for #8 cylinder, turn the crankshaft clockwise another 1/4 turn. That will put the piston of #4 cylinder (second from front, passenger side) at top dead center and you can adjust both intake and exhaust rockers for that cylinder. Following this, turn the crankshaft another 1/4 turn and adjust intake and exhaust rockers on cylinder #3 (second from front, driver's side). Another 1/4 turn and adjust both on cylinder #6 (third from front, passenger side), another 1/4 turn and adjust both on cylinder #5 (third from front, driver's side), another 1/4 turn and adjust both on cylinder # 7 (rear, driver's side) and finally, another 1/4 turn and adjust both on cylinder #2 (front, passenger's side). This routine will work on any motor if you start out on #1 and follow the firing order, turning the crank 1/4 turn in between adjustments to move on to the next cylinder in the firing order. Be careful on Fords, they have a different cylinder numbering system and several different firing orders, depending on the engine family. |
*13. Failure to inspect the distributor drive gear for wear. Too much wear can allow the cam to walk in its cam bore and allow a lobe to contact an adjacent lifter. | *13. Failure to inspect the distributor drive gear for wear. Too much wear can allow the cam to walk in its cam bore and allow a lobe to contact an adjacent lifter. | ||
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