410 LA small block will not rev past 6000

20+ years ago we chased our tales looking for more rpm out of my friends Stocker.
Adding spring pressure did nothing…….. in fact it seemed like when things went in the crapper, it happened more abruptly.

We were trying different cams from different suppliers, different ramp rates, etc……. Without success.
It was good till about 6k, but we really needed another 500rpm to get the car thru the finish line clean.

At that point, I was pretty sure the lobe designs and springs weren’t the issue.
So, we tested Hyd lifters vs solid lifters on the dyno.
Poof……with the solids, the engine would run to 7k no problem.