The 48-51 Truck Shop Manual has two valve clearance settings.
Normal and Heavy Duty.

Normal: Intake .006 to.008
Exhaust .013 to .015

Heavy Duty: Intake .010
Exhaust .020

There is no mention of why.


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission