I have found thru the years that adjusting the hydraulic lifters up from the bottom about a half turn makes more power. Oil is incompressible, but air is not. Once an engine has run and especially at high RPM air is entrained(mixed into the oil), the air in the lifter compresses and that results in lower effective lift and duration and consequently, less power. I first discovered this effect in 1985 and have been adjusting all of my HIGH PERFORMANCE cams from my shop this way since then. Stock or low performance, why bother, do it the easy/ stock way. But if you are "chasing the numbers" like me and most of my customers, adjusting from the bottom makes more HP and sense to me. I also drain any oil from new or used lifters by using my drill press or mill as an arbor press, a short piece of pushrod in the chuck, a block of wood, and a rag or pie pan to catch the oil are all you need. Now you don't have to wait with the cam on lift and collapse the lifters in the engine before adjusting them, its quite a timesaver. You don't have to worry about the "old wives tale" of lifters pumping up, with the correct spring pressure for the cam, and modern springs that was a thing of the past. A lifter can only pump up with excessive oil pressure, (not a Harley trait) or valve float, allowing the lifter to pump up to take up the excessive clearance. One more comment: for those of us with machine shops that build both race/performance V-8s AND Harleys, we know that for the same lift/duration cams in both types of engines, the Harleys call for 50 to 80 more pounds of spring pressure. The higher spring pressure will always collapse the lifter more than lesser pressure and result in less HP. EVOs and Twin Cams HDs use Chevy lifters.
Don't believe the air in the oil? Buy a milk shake or Orange Julius, don't drink it, and let it sit on the bench for an hour or so. The level is lower by the amount of air whipped into the milk shake. The crank diameter is way bigger than the little deal on the bottom of the milk shake maker, and they don't whip the shake for as long as you are riding. Think about it. Just some random thoughts from the TIMINATOR
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Topic: S&S Lifters / Pushrod adjustment (Read 6447 times)