my truck had a code for misfire on cylinder 7. I changed the plug and coil pack and it ran fine. But when warmed up it had what sounded like a rocker arm slapping. But in neutral or park when revved even warm no sound. Today my wife drove it to town and it died. Serious tapping in top end and codes for cyl 7 and 5 misfire. As well as multiple random misfires. Cant keep it running long enough to scan for individual misfires. Any ideas or help is greatly appreciated.
also has a code for coil 7 circuit open.

 

Swap coils on 3 and 7, see if that code moves. I think you are going to need to pull the valve covers, and have a look at your rockers. If you are high mileage, good chance the lifters have failed.

 

Has a crate engine from Napa with only 52k on it. Is what I was told by previous owner. But no physical proof.

 

Uh huh.

Trust, but verify. Check the rockers.

 

im going to tear it down this weekend. At the risk of sounding stupid. If the rockers were kicked off Should I replace everything under valve cover. Cams included? I'd do both sides.

 

Depends on what condition the cams are in. If they are ok, just go after the lifters, and any parts that look like they may have been damaged. And yes, definitely do both sides.

 

if this were the 5.2 or the 5.9 I'd know what im dealing with. But this over head cam stuff is new to me. Last question before this weekend. Is there a chance it could have bent a valve if it threw a rocker?

 

Anything is possible. Have a look, see what you find. Take it from there. Generally, they just spit out the rocker, and you don't have to pull the head. Sometimes though, the precipitating event is a dropped valve seat..... that requires a bit more work.....