I have a built 383 with the old school MP 108CL 284/484 cam in it. I installed the Rhodes lifters in it to help with vacuum for the power brakes. (The vacuum is about 10-11 at idle and 7-8 in gear) I;ve run 20-50 oil since it was broke in but someone said to try 10-30 instead so that the lifers will bleed down quicker. So, I did that today and went to start the motor and it would'nt idle.............Hmmmmmmmmmmm. I ended up cranking up the idle screw alittle and Im alittle confused that the car now runs diffrent........Not sure if its better but it runs diffrent.

Did I do the right thing?

actually with thinner oil you will build up oil pressure faster so the lifters pump up faster and stay pumped up at a lower rpm.
my hemi has rhodes lifters and it runs better with 20W50 oil than with 15W40 oil.