Questions on 440 engine Rocker shaft shims?

[Pops1967GTX]

upon removal of my valve covers & inspection of my 440 engine. I found double valve cover gaskets & shims under my rocker arm shafts. Looking for answers to the why?

I found this on web...
Back in the day, rocker shims were used frequently to decrease the stock preload on hydraulic lifters with the stock valve gear. I have an old Motion Performance handbook from the 70's that goes through the procedure for that very reason.

I will set up the shaft, by shimming them to get the narrowest contact patch across the rocker. The narrowest contact patch will result (98%) of time in the greatest amount of valve lift. I have tested a few different methods and the greatest amount of lift/narrowest contact seams to result in the least amount of guide ware. I personally don't care if it's centered or not, as long as it's not more then .060" off center.

Once I get that all established I will get my pushrod length by truning the adjuster out 1 full turn and measure it at that length.

 

[Darter6]

At one time Mopar Performance sold shim kits,may still do.
Under the rockershaft was usually done when heads/block was shaved to correct pushrod length/preload on non adjustable rockers.

 

[RemCharger]

I will set up the shaft, by shimming them to get the narrowest contact patch across the rocker. The narrowest contact patch will result (98%) of time in the greatest amount of valve lift. I have tested a few different methods and the greatest amount of lift/narrowest contact seams to result in the least amount of guide ware. I personally don't care if it's centered or not, as long as it's not more then .060" off center.

Once I get that all established I will get my pushrod length by truning the adjuster out 1 full turn and measure it at that length.

You're getting really deep with this.
Shimming is for pushrod preload altering only.
Not for trying to correct the stock flimsy rocker arm sweep pattern.
If your preload is acceptable currently, leave it alone.
If you're trying to change the pushrod length, pull the shims and start back from stock.
If you're trying to achieve a higher max rpm with the hyd cam( as shimming was intended for), put it back to stock and measure the pushrod length for a min .020 on the tightest one. That will give you the best durability.
True shims should be a special taper to fit in the rocker stand so you don't spilt the shaft cradle. Then you're really screwed.
That's the part most novices aren't aware of.

 

[Runcharger]

10 potential oil leaks as well.

 

[440sixpackracer]

The shims will sometimes break the stands. Use caution with the shims