I apologize if this has been discussed before - I could not find it in the post I searched. I had a cam phaser fail completely. I have the front of the engine off and I have ordered the Livernois OEM phasers with the lockouts installed. I am wanting to check the engine for valve damage from the phaser failing. What are some test I can do? When the new phasers are installed - will I be able to know if a valve is hitting the piston when I crank it over by hand?

 

Since you have the valve covers off already, start by closely inspecting the valves. Look for bent/broken valves, springs and rocker arms. Check the lobes for excessive scoring. I would pull the camshafts off and check the journals also. With the camshafts off, you can check the lash adjusters by pushing them down. If they go down and spring back up quickly, they should be ok. If they won't go down, are extremely hard to push down, or won't pop back up, replace them. If you find a bad lash adjuster, recheck that valve, rocker, and lobe thoroughly.
With the engine assembled, if you turn the crank by hand, you will definitely know if a valve is hitting a piston. You won't be able to turn the crank without a cheater bar, if at all.
If you do decide to remove the cams, I suggest making two marks on each cap lined up with two marks the camshaft, and mark where the caps go and which direcrion. That will make it much easier to put back together correctly.

 

I would suggest rotating the cams instead of the crank. When rotating the crank you are using a breaker bar and also moving alot of mass. It is to easy to bend a valve using this method there is simply to much force involved and valves can get bent before you realize it. Put a wrench on the front cam gear bolt and slowly turn the cam as soon as resistance is met stop. You will have to set your crank keyway at any 90 deg position (12:00,3:00,6:00,9:00) before the pistons are all low enough in the bores to provide clearance for the cams to be completely and freely rotated. You can then turn the cams all day long while leaving the crank in one of these positions. This is with a 4.6 the 5.4 has lower piston to deck heights and provides better clearance. Also once all the valves are closed on either or both heads you can perform a leakdown test. While listening for air leakage as well as observing the air gauge meter drop you can determine what valve is bent either intake or exhaust. If no air is leaking in any cyls then you should be good to go.

 

Dynotech brings up a good point.
I neglected to mention that I like to pull the plugs when I'm going to have to rotate the crank. With the plugs out, there is no compression to fight, and you don't need a cheater bar or breaker bar.