I like to use the old rule of .0010 clearances for each one inch of crankshaft journal diameter regardless of oil weight used on my street motors and drag race motors twocents
Oil does two things in the motor, it lubricates and it cools. Thinner oil moves quicker when cold and on start up work
I now use 5w20WT on most of my builds, street or race up shruggy
I saw 8 HP loss due to colder oil temps. on the first motor I dyno tested, it gained 8Hp going from 130 F oil temps to 170F oil temps with straight 30 WT oil shock I tried 10W30WT oil on another motor later on a different dyno , same brand, and saw 3 HP going from 130F to 165 F. I saw no change using 5W20Wt and 5W30WT oils from 80 F to 220 F oil temps. work
EDITED: I don't build or race high RPM (above 8000 RPM) motors like NASCAR or any other extended high RPM motors like them so I have no real or valid input based on my experiences on those type motors!
I would love to work with a team that does have a successful motor program to help me learn more about that end of racing luck
Thanks Brad for posting this up

Last edited by Cab_Burge; 11/15/16 04:56 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)