My engine makes alot of lifter noise when cold if I use 15w-50. It likes Valvoline VR1, 10W-30, which as mentioned, was the recommended weight.
BTW: The first number is the cold viscosity and the only number that is influenced by
outside air temps (if your cooling system is working properly). A lower number flows better when cold. A high second number like 50 (hot viscosity) is usually ment for racing applications but can be good for older engines since tolerances are greater than modern engines.
Unfortunatly the EPA took our ZDDP out of regular oil and one of the few oils that has enough for our flat tappet engines is Val VR1 racing oil (all weights) and Mobile 1 in 15w-50 weight only. To get enough Zddp with your brand of normal oil you will have to add it.
Goto cam-shield.com to read more.
71 Mach1 351C-4v TKO 5-speed
Eleanor clone (the origional movie)