425 Oldsmobile

I have a 66 Olds 425, just rebuilt... most all new parts, I only have about 30 miles on the new motor. My situation is after it sits for a time, like overnight, or even after I drive it and park it, then like 30 minuets later.. sometimes the rockers click, sounds like just 1 (num 7) for about 10-20 seconds then goes away and sounds good. This motor has non adjustable rockers, Im currently running 5-30 oil, thinking 10w-30 might help some but any other thoughts?


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A few things come to mind. First, these motors were designed to run on 10W-40, so you may want to change your oil. One lifter may have been manufactured on the loose side of the tolerances and the thinner oil allows it to bleed down. The other thing is that due to the non-adjustable valvetrain, Olds heads are very sensitive to installed valve stem height. There's even a Kent-Moore gauge tool to check this. Chevy-centric machine shops are often not aware of this and frequently get it wrong.