Did you change the timing set?
If so what did you use?
There are some flaws in that method of adjusting pre-load on the lifters.
The goal is to make sure that you are making adjustments with the lifter well onto the base-circle of the camshaft.
Following the firing order will work with a marked balancer, you can also set half of the lifters at TDC on the #1 firing position then again on #6. Anyone wanting to use that method can Google up which valves to adjust at each position.
Following the firing order it is easy to get confused as you also have to know the firing order of the engine and make sure that you are on the correct cylinder when adjustments are made. The balancer is also marked in four places at 90 degrees, most will not be so you have to make sure that happens correctly.
One must also take lifter travel into consideration. Some lifters have more travel than others but typically 1/2 turn down from zero lash will be fine. Some "high performance" short travel lifters are designed to be ran with less preload.
In any and all cases here I will compute lifter plunger travel first, especially with new lifters and I've seen variations from about .060" of travel to .150". This is happening these days because there are a lot of manufacturers that have stepped into the lifter business and quite a bit of what we see now is coming from off-shore. There are also a lot of different types of lifters out there, so very little if any "standards" in that industry these days.
The off-shore lifters are horrible and to be avoided. Problem is that there is also a good bit of "re-boxing" going on, but that's a story for another thread on another day. In any and all cases IF you are using a flat tappet camshaft make sure it's getting top quality USA made lifters on it or you will have issues.
Excessive noise is one of them, and lifter/lobe failure is also very common and not a day goes buy you don't read about someone having an issue on one of the Forums. The cam lobe failure thing is directly related to using bad lifters, although there are others that are blaming break in procedures, not removing inner springs during break-in, break in lube, lack of trace metal particles in modern oil (zinc), and about half a dozen other things which have nothing to do with the issues we are seeing.
These cheap imported lifters are NOT made of good quality high nickel iron, nor are they finished and crowned correctly so they spin in operation.
The info above doesn't necessarily relate directly to this thread, but put up there to educate folks as to what's going on with these things.......Cliff