The V8 engine: No, not the javascript one (part two)

It's been a while since I felt like writing about anything, which is a shame because I do enjoy writing when I feel in the mood. Mostly this entry is about the long and tortured road to finishing the engine in my Chrysler 300C.

A proper post-mortem

In the last post, I have a shot of the destroyed piston which was causing most of the problems with the big Hemi. Once the engine was out of the car and on a stand, a mate and I carefully removed the sump to reveal a pile of bits. Two of the other cylinders were also missing parts of their crown but weren't damaged like #6 was. The bits in the sump were largely expected: pieces of piston crown; oil ring pieces; compression ring pieces. Assembled on the bench they look like around enough parts that were missing from #6 piston, but not the pieces that were missing from #4 and #2. Looking carefully at the other pistons, some carried evidence of valve strike. It was also apparent that this engine does not belong with this car, the Hemi is a 2009 "Eagle", not the 2006 original which made ordering parts somewhat difficult.

So my best guess as to what happened is that at some point the timing chain broke (a known issue on the 2009), the pistons and valves met in an unhappy dance and some unknown mechanic decided to slap it back together. Making some further assumptions, it looks like the heads and sump were removed, broken pieces of #6, #4 and #2 were removed, the pistons were not replaced and the whole thing was shoved back together with a giant amount of silicon gasket maker.

Some way further down the road, #6 piston disintegrated, pushing a piece of piston into the inlet valve, causing it to bend and scoring the valve seat. The rest of the piston fell into the sump. It's surprising it ran at all - I mean other than running on 7 cylinders it idled perfectly and only really started to push a massive smoke screen when taken over 2000rpm. I felt it was important to try to work out the nature of the failure before I started the rebuild as I didn't want it to re-occur.

I had, of course, vastly over-estimated my ability to rebuild this engine. In between waiting for parts to be delivered I managed to screw up in some surprisingly creative ways:

  • Mixed up the left and right head gaskets, resulting in an engine that ran but spewed coolant out the sides.
  • Did a stupid thing with one of the oil control rings, resulting in oil dribbling out of the exhaust. I had to drop the sump and replace the ring from underneath.
  • Did not re-install the oil pickup correctly when replacing the ring, resulting in zero compression and a car that ran on 4 cylinders
  • On the third re-assembly managed to get one of the push rods in the wrong place, resulting in no oil pressure to the lifters

The engine survived all of my screw ups and now purrs like a kitten although I really feel like all of those self inflicted errors could have been completely avoided with a little more attention to detail. On the upside, I can now tear down and rebuild the top end of a Hemi in my sleep.

The process of rebuilding the Hemi is detailed here as I asked for help from a specialised forum.

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