Hey guys I'm new here. We just reassembled a 2007 hemi. All is good and it started right up but had a misfire on cyclender 6. Which is a mds lifter hole. Did the easy things already. Swapped the coil pack and checked plugs. Still on hole 6. Did a compression test and have zero. Pulled value cover off again and inspected everything. When turning the motor over the intake value doesn't move. Forst thought was a collapsed mds lifter. Pulled rocker arm and checked pushrod for movement and it functions properly. Could a broken value spring cause the value to not move at all?

 

Take off the spring, and see how the valve feels. Does it look like it is coming back up all the way? If the piston whacked it, it's gonna be bent, and certainly won't close all the way.

 

how do i keep the valve from falling into the piston?

 

Have the piston close to TDC. And pay attention. You want to be able to move the valve a bit... but, you don't want it to drop down so far that the valve stem disappears into the guide. I have had some success with a pencil magnet to pull 'em back up when that happens.

 

​​​The MDS lifter will purposely collapse when the lifter tunnel is pressurized with oil. The oil pressure pushes in the pins on the side of the lifter which disengages the large internal spring. The lifter will ride the cam without opening the valve.
Could also be a wiped cam.

 

This is key. You can visually verify that a piston is at TDC. Pull the spark plug and stick a long screwdriver down the hole so it sits on top of the piston. Rotate the engine till the screwdriver rides up to it's highest point. Since a hemi is an interference engine, the piston should meet the valve and support it.