Hey guys, thanks for having me. I used to be somewhat active as 460Eagle back in 2008 or so. I've long forgotten the information associated with that account so I'm starting fresh..

I'm looking for some council. A family member owned this 93' F150 for many years... Somewhere around 200k miles he melted #5 piston (5.8L)... Truck was a work beater, and so he found another high mile 160k+ engine for it. It was swapped in after doing the basics that anybody would do when the engine is out of the truck (timing set, gaskets, etc.). Truck ran decent for many years after that. He ended up retiring the truck, at which point I started driving it occasionally to pick up lumber for projects, etc... This engine met the same fate. #5 piston melted. I pulled the engine out way back in 2017, and after tearing it down, I noticed the bores were already .060. Engine was trash. I parked the truck in the back.

Fast forward to today. I've rebuilt a fresh 5.8L. I'm about ready to put it in the truck. Nothing fancy. Stock rebuild. This one is nicer. it's a later engine with roller lifters. Odds and ends need to be finished, including applying a generous coat of black paint to the engine, and fixing some issues in the engine bay that are easier fixed without the engine in place.

I'm wondering if you guys could shed some light on the melting of piston #5. the other 7 pistons looked fine in both engines. I believe the issue is not with the engines, but electrical or emissions related. I'd hate to burn up this engine, so I really need to figure out the root cause for this issue.

I'll attach a few pictures. Thanks guys.