FYI > Posted this in the other thread too:
Though that there may be some interest in what is inside the DOD DEAC lifters, and potential extra points of failure:
Left hand side shows the main lifter body with the smaller lifter oiling port, and the larger DOD control port.
Above the lifter body is the DOD plunger return spring and retainer, and washer.
On the right hand side is the DOD plunger, showing the activation pistons and preload spring, and above that the pushrod seat, oil metering plate, lifter plunger with lifter check valve and pre load spring.
The activation pistons measure 0.275" in diameter, and require around 1 lb of force to compress to fully flush with the DOD plunger. (around 16 psi?)
When they are fully flush, they dis-engage the DOD DEAC plunger which carries the lifter plunger and pushrod seat, from the main lifter body, allowing the main lifter body to ride up and down on the cam, without transferring any motion to the pushrod.
Oil pressure is applied via the DOD DEAC solenoids in the valley cover, under ECM control, which depresses the activation pistons so they dis-engage from a slot in side the main lifter body.
When the ECM commands re-activation of the 4 DOD cylinders, the oil pressure is released which allows the activation pistons to extend under pressure of the their pre load spring and be pulled by the return spring back to their normal operating position and re-engage the main lifter body allowing the lifter to operate normally.
cheers!