Put on your blindfolds, into the inner and outer world of valve springs we go!

TT5.9mag said

I’ll add, with a flat Tappet it’s crucial to detail the lifter bores on assembly and make sure the lifters are free to rotate. With a hydraulic flat, it’s crucial to prime the oil system before cranking. And (most people don’t) crank in a bunch of timing.

Click to expand...

Many blocks are cooked and it leaves a rougher finish everywhere that isn't freshly machined. It's always a good idea to lightly 'finger twist' hone with some 500-800 grit paper in the lifter bores before cleaning & assembly.

Always makes sure they spin easy.
Always check the oil feed hole sizing in each lifter bore. They are sometimes not as big or have a ton of flashing like the late 70's 318's.