I am not familiar with the TO30, however on a M.F. 65 (continental gas engine) the rocker shaft can be installed so no oil gets to the rockers. Rotate the shaft one half turn and you will get oil, but not what I would call a gusher.
The I.T. service manual instructs readers to install the shaft so no oil is delivered.
The Massey service manual gives directions that yield flow to the rockers.