Hi, I have two questions to ask about my Monte. Something has broken inside the engine. I hammered down on it at around 35 mph and just after it downshifted to low, it lost a cylinder. Dead cylinder. Now the only noise its making is sort of a rattle. I think the timing is fine because it runs fine otherwise. With a screwdriver/ear rig it sounds like its in the valve cover or maybe even pushrod area. I'm a troubleshooter and feel like I should know this sound. It's not hammering, not a lifter tap, nor is it grinding. Sounds more like a rocker arm, valve spring, rattle.
I had the intake gasket replaced 2 years ago because it leaked. I notice now there's water in the oil again. I must need another gasket now.
The questions... can you point me to the rattle? And is there a good way to stop the recurring intake leaks?
I suspect the rattle is a result of poor lubrication near the intake leak.
Thanks.

Broken valve spring or punched through rocker arm would cause a noise like this. You will need to pull the valve cover.

Correct!
You need further diagnosis on both the noise and the mixing of coolant into the oil.
Howevere, there is a bulletin for a new intake gasket. Do you know the part number that was used last repair? That may need replaced with the updated gasket but there may be an entirely different problem. Best take this in on a flat bed rather than risk further damage to the engine.