Install adjustable rocker arms so that you can properly adjust/set the hydraulic cam follower plunger depth.
Why reinvent the wheel? Stock is fine,
Dan, here is what I was suggesting:
These are hydraulic cam follows (aka lifters), correct?
The cam follower's internal "plunger" or "piston" has .XXX" distance of usable travel..... correct?
(I do not know what this dimension is for the 440 engine..... it's about .100" for the GM V engines)
Nonetheless, basically all hydraulic flat tappet cam followers function pretty much the same.
Here's a neat little GIF file that shows the plunger travel, how the body is charged with oil, the check-disc function, etc, during one cycling.
http://www.youtube.com/watch?feature=player_detailpage&v=lorANZ1Tptw
(the GIF gets sticky at one point, so you may need to move your cursor over it a bit)
Chrysler designed their cam followers and their non-adjustable rocker arm system to take this plunger travel into account.
The goal is to place the plunger at mid distance between bottoming out and topping out, as to offer the hydraulic function within this range.
If when all components are assembled, these components (via the push rod) place the plunger at the desired depth (as per Chrysler's engineers), and then ZERO valve stem/rocker arm lash can be achieved...... would you agree?
Now..... what if normal wear, a worn cam, or a change here and there, causes the OEM dimensions to become somewhat out of range?
IOW, if the plunger is now topping out, it may no longer be able to maitain ZERO lash between the valve stem and rocker arm tip..... hense the rocker arm rattle or noise that the OP describes!
New cam followers may not completely solve this issue.
If the non-adjustable system was taken out of the equation in lieu of an adjustable system, the user can now custom adjust the plunger depth for each cam follower.
Just to be clear... there's nothing wrong with the OEM non-adjustable system as long as all factory dimensions are being held.
Ford has used this, Chrysler has used this, and I'm sure that others have also.
Personally, I prefer being able to adjust these.
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