Viscosity and hydraulic lifters

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Jan 16, 2003
Shippensburg, PA
Here's a fun topic for discussion:

How does viscosity affect the leakdown rate of hydraulic lifters? leakdown rate can have an impact on valve events, and my intuition tells me that higher viscosity oils will bleed down slower.

How does this affect performance? Is it possible that one could GAIN 1-2 HP by running heavier viscosity?

Anyone know anything about this???
I remember reading something as such, especially with the rapid leakdown lifters. Call comp cams for more info.
You won't gain any power by using a heavier oil. In fact, it can actually cause valve float. Ford's zetec engine is bad for that if used with 10-40 or heavier oil (so I've been told by ford mechanics).
I was looking at some OEM roller lifter blue prints the other day. It gives the spec. for the oil to be used and the exact amount of time and amount of leak down acceptable. THe duration for the leakdown test was so long that any single valve event would not be effected. I can also tell you that most lifters in older applications function just fine on 20W50. One OEM race shop actualy tells you to run 20W50 in the engine that OEM claims must have 5W30! Same lifters, same oil pump, same bearings. Makes you wounder????
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