What oil to use?

What oil should I be using? I use Valvoline racing oil, but what wt oil. Multie grade or straight wt. Then 10w-30, 10w-40 10w-50? One car is a warmed up 383 and the other is a 472 Hemi with 11.5-1.
Thanks

I use 20-50 VR-1 oil in my flat tappet engine wit good results
Gus

It depends on bearing clearnace and other factors. One way to tell is hot oil pressure. I look for at least 20PSI at idle and steady readings above 1500 RPM - around 60 PSI. I'd start with 10W30. That should be plenty for the 383 if clearances are near stock. The other engine may like 15W40 or 20W50 if clearances are bigger.

Just make sure the oil you choose has enough zinc for your flat tappet or add ZDPP.