I found that those particular lifters don’t have much for metering the oil to the top end compared to other brands, they will flood the top end with oil. I tried running them with no restrictors and I had trouble. After a full throttle blast or constant RPMs, getting back on the throttle the oil pressure would not recover very well, like the pump was sucking air. Was pretty nerve racking. That was with a 7 quart oil pan and iron heads, which don’t usually have problems with return oil. I restricted the lifter bores with .040”s and the problem when away.
Restricting the pushrods on a SR cam that runs lash you end up spraying extra oil back into the rotating assembly. Especially when the oil metering in the lifter isn’t great. I am sure it still gets plenty of oil to the top end for drag racing. A HR lifter is pretty much coupled up to the pushrod all the time, it would provide more oil the the top end than a SR lifter with the same restrict pushrod. Personally I think restricted pushrods aren’t a great idea on street engines with SR cam, designed more for HR setups. Those lifters need restricting though, restrict pushrods would be better than nothing.
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