When I worked in the auto parts business. I would hear many types of "clean outs". There are 2 that I have used, one is Motor Flush and the other is a pint of ATF added to the oil and driven for a day or two then change your oil. However, I did neither of these on my 49 when I got it. I pulled the valve cover and found that the top end was getting no oil at all. I cleaned out all the return passages and then sucked the oil supply line clear of all the sludge that it had. Next I pulled the oil pan and cleaned everything. While I had the pan off I inspected the oil Pump. It showed signs of wear and while I could have reinstalled I decided to replace it and not chance it.
Pulling the side cover and valve cover will give you a good idea to what the state of Sludge build up is on your engine..
Good luck
