I have been battling this for awhile,its the front exhaust tube I will get it fixed and it will hold for a while and then start to leak .I have went to a smaller push rod because of the rub and i have shimed under the tube spring to tighten it up with no luck.I noticed today that the end where the push tube meets the rocker box the tube isnt sitting flatand thats where my leak is coming from ,the tube end looks good and the recess in the rocker box is clean but when I extend the tube from the block to rocker box there is a 3/16 gap from one side to the other in the rocker box?!?! has anyone had this problem?

 

They changed the upper tube a couple times as shovels got older and the lip on the sealing edge is different widths on them . What year & are you using corks , rubber , or o-rings on yours ?

 

Causes:
Bad tube, could be distorted
Bad spring
Bad seals
Lifter and roller misaligned (make sure oil hole is toward the center)
Go to your local indy and find a stock tube and try it. If what you have is aftermarket, it may not be true.