Have you got adjustable valve gear? What is your lifter preload?
Any time you shut your engine off, there will be at least 4 valves open to some degree or another. And I suppose, the springs,over time, could bleed the lifters down while sitting;and of course then you get the clatter at start up.
If you go to Hughes or Comp or perhaps some others, you can read there that the recommended lifter preloads are often .080 or more. If you consider that this is near the bottom of the plunger travel, if or when they bleed down, they can only move perhaps .040 to .050 so clatter is minimized. But the flipside of that is that if the springs lose control at high-rpm, and the lifters pump up, then suddenly the valves are .080 or more further open, and not closing at all.
So if you don't allow for that during the build, then the valves go crashing into the pistons and you are having a very bad day.
But if you did allow for that, then as long as the engine is wound up, it will continue to run,allbeit way under powered. As the Rs come down, there will come a point where the engine will sputter and die, because the valves are not closing..... and a restart will not be possible until the lifters bleed down. And since at shut down only 4 lifters will be under pressure, you still having a bad day.
So IMO, that .080 or more spec is...... um ....... not for me.
But what is the alternative?
Well IMO, running close to .020 is a better idea, because
1) the lifter can only pump up .020. So yes the valves will still not close when pumped up, but the likelihood of piston to valve contact is much reduced. And
2) they bleed down faster afterwards, cuz they only have .020 to go, and not .080.
The downside is that if they bleed down overnight, you may get a long period of time during which they clatter.Why is that? Well with a plunger travel around .135 and a preload of just .020, it is theoretically possible for the plunger to have to be pumped up .115 in the morning..... and you could have up to 4 lifters in that condition. Another downside is that you get to re-adjust them after cam break-in, as they settle in.
So to combat the clatter, I got me some anti pump-ups, and a hi-volume oil-pump. I then adjusted the valves to .020 preload. So now I have at least 7200 rpm capability (where I shift at a lot), and have never had pump-up, nor clatter ( ignoring every spring), don't have to worry about bent valves, and I get long enough periods between lash adjustments. And the hi-volume pump is there just in case,lol.
I ran 15W40 for a bit but the hi-volume pump would blow the filter off the seat,at rpm, and puke oil onto the header under it. I though that might have a catastrophic ending; so I took the engine apart and did some oiling mods, to let the oil flow more freely.
Now I run 10W30, any brand, and drop a few ounces of ZDDP in it just to keep the lobes happy. Yes any brand, whatever is on sale. I know, I heard all the arguments and read all the oil specs,But I wanted to freshen my engine in about 2006; so hey, let's see if all this oil-hype is true; I said. And here we are a dozen years later, and thousands and thousands of miles later, and I'm still waiting for the cam-lobes to fall off.
Your results may vary.