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techtalk:evo:engmech04c [2019/10/08 12:53] hippysmack [Bolt Installation Sequence] |
techtalk:evo:engmech04c [2019/10/08 13:25] hippysmack |
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| ===== Check Pushrod Length ===== | ===== Check Pushrod Length ===== | ||
| + | A hydraulic lifter has a plunger in it's body that has about .200" of movement. ((http://www.hammerperf.com/ttpushrodlength.shtml)) Oil sits under the plunger and pushes it up to take the slack out of the valve train. \\ | ||
| + | In the ideal world, the plunger is approximately centered in it's travel, meaning it's preloaded about .100". \\ | ||
| + | So in theory,\\ | ||
| + | It could move up, thus lengthening the effective length of the lifter to compensate for a pushrod that's up to .100" too short. \\ | ||
| + | And likewise, it could move down, thus shortening the effective length of the lifter to compensate for a pushrod that's up to .100" too long. \\ | ||
| + | This self adjusting action is also useful for compensating for changes in needed pushrod length due to engine temp variations. \\ | ||
| + | As the motor heats up, the top end grows and the lifter automatically takes up the slack. \\ | ||
| + | In reality, \\ | ||
| + | The useful operating range of the lifter plunger is only about .050" in either direction away from centered (.050" to .150" of preload). \\ | ||
| + | Outside of this range, the self adjusting function doesn't work nearly as well. | ||
| + | You can measure lifter pre-load to determine if the pushrods are in the size range needed. This method will get you close. ((http://www.hammerperf.com/ttpushrodlength.shtml)) \\ | ||
| + | The cam lobes should be down (as they should be when installing a rocker box). \\ | ||
| + | Set the pushrods in place (the longer one goes on the exhaust) and then place the gasket and rocker box on top installing the four big screws only. \\ | ||
| + | Finger tighten the left (spark plug) side, while making sure the right side is resting with the upper pushrod ends sitting in the cups on the rocker arms. \\ | ||
| + | Use a caliper to measure how much gap you have between the rocker box and the rocker box gasket. \\ | ||
| + | The lifter preload should be app. .100" but anywhere between .050" and .150" should work. \\ | ||
| + | Aftermarket pushrods can be purchased in longer or shorter lengths than stock ones to get the measurement within .100". | ||
| + | |||
| + | {{:techtalk:evo:engmech:lifter_preload_by_aswracing.jpg?direct&300|}} ((photo by aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=322680&page=5)) \\ | ||
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