Because I have a 1975 250 in my 1965 C10, I have both the 1963 & 1974-76 shop manuals. I think it interesting that they contain a different method for adjusting valves.
The 1963 manual says to adjust both valves when cylinders are at top of compression stroke. The 1974-76 manual says to adjust both valves of Nos. 1 and 6 like that, but the others one at a time as shown on attached.
I was just wondering why the change? In the end the results are the same.
