Fig. 63.6
This modification to the cover is to insure that the relief spring and piston does not come out under very high pressure. Remove the roll-pin which holds the pressure relief spring and piston in, tap this hole for a screw-in plug See Arrow "B" in Fig. 63.6. Before you screw the plug in for the final time make sure you drill a small relief hole through the cover (See Arrow "A") into the backside of the pressure relief passage behind the relief piston, since any oil that seeps past the relief piston can cause the pressure relief not to function this hole is critical.