Ok, I set the valves to zero lash the engine has a very noticeable rattle. I think I read that they will sound like a bucket of bolts but I don't recall the sound level being this loud. I rechecked the clearance twice. The engine pulls real strong. I'm all ears!
Brian

shouldnt really sound like a bucket o bolts. do you have hydraulic lifters? If so, and it's been a while since the car was driven, it can sound really noisy till the lifters inflate with oil

Solid lifters.
Brian

Should sound very smooth. No rattles.

I don't understand zero lash with steel pushrods ,makes sense on a hyd lifter motor but on a solid tappet motor what happens when the engine heats up and expands width wise ?,surely the expansion rate would be different between steel and alloy pushrods ???.
I'am old but I never stop learning

Case ans heads are aluminium, they expand more than steel.

Check the clearance between the rockers and spacers. If it is a lot then that makes noise to.

Jake explains it that way....with lash at zero with engine cold it'll open up to .004-.006 with the engine hot, so you'll hear a bit of the usual ticking from the valves especially with thin oil....BP 20/50 may keep it a bit quieter...

When should you use 0 valve lash vs the .006/.008?

Only with chrome moly push rods.
I going to check again for a loose rocker today before cars and coffee.
Brian

Running .006 on steel PR will make them noisier.
They are noticeably noisier cold and you can still hear it warm, especially if you have a quiet exhaust.