I bought a 2008 Ram 1500, the engine was knocking bad.

Bought a used motor , installed it and it had a slight misfire. Idles smooth, but put it in gear, there is a misfire. Scan says misfire on #1 cylinder. Disconnect coil and misfire is noticeable by %100.

Did a compression test, 45psi, did a wet test and compression went to 100 psi.

I pulled the head and there is a big chunk of piston missing above wrist pin. Valves have not been touched.

On the head on both dudes of valves the head is chewed up.

Any ideas on the problem?


Cylinder with chunk out of piston.

Cylinder head showing damage opposite valves

 

Detonation, broken ring lands. Ran super lean.

 

What would cause the lands to break or the detonation?

 

That cylinder wall is pitted and rusty. Ring could have snagged on a rough spot.

 

PossibleI, I was entertaining the idea that a connecting stretched. But the valves didn't get touched.

strangely enough, the broken piston pieces didn't touch the valves either

 

That had to make one heck of a racket......

 

So this used motor, was that from a private seller? Seems unscrupulous.

 

I'm thinking what you're seeing is the reflection of the top of the piston.

 

If you didn't trade in your original knocking engine, might be able to get one good piston out of that one and get back on the road. Have the head checked though, due to piston pieces pounding it.

 

Not at all when I got it. My buddy and I installed it, fired it up, lifters clacked till they got primed up and it ran smooth.

Then you put your foot on brake pedal and put in gear you could feel the misfire. But put it back in park, disconnect coil definate misfire, plug coil back in ran smooth.

That's when we did dry and wet compression test. Compression jumped up. So this happened before I got the motor for sure.