[Eson]

Hey fellas,

After four previous S54 powered cars, my luck ran out with what I thought would be my most robust one yet -

2007 Z4M Coupe. Street driven, 42k miles, 3-5k oil change/15k valve adjustment intervals documented since new. Most recent oil change and valve adjustment was 1,400 miles prior to this mishap...

After previously driving spiritedly (though no overrev, money-shift, etc...), my motor began knocking in 4th gear at 2k RPM. My initial thought was a rod bearing very prematurely spun as it was a consistent "slap" and the typical go-to S54 issue, but that surprisingly was not the case ---

After dropping the front subframe, removing the oil pan, inspecting the rod bearings, main bearings, and crank, I pulled the valve cover and plugs where I took a borescope down cylinder #2 and found that the top of the piston was polished clean from hitting the cylinder head. I have not yet been able to determine why, though I did NOT spin a bearing. I'm going back under to see if there is play in the rod, if a wrist pin bushing broke, etc. Regardless, the piston is slapping.

This leaves me with essentially four options -

1.) Rebuild at my trusted local shop and have the machine work done at a nearby reputable machinist. This would consist of OEM, CP pistons, Carillo rods, and Schrick cams, etc... $14k

2.) Source a used S54 for $4-5k, spend $$$ on Beisan VANOS, bearings, cams, and airbox for a total of roughly $10k.. all while hoping lightning doesn't strike twice in the same place.

3.) Buy a BMW crate motor for $15k.

4.) Have Lang Racing build me a mildly modified motor (CP pistons, carillo rods, Beisan VANOS, 288/280 cams, DLC rockers, widened rod journals, etc, etc).

5.) Dinan. $$$$$$, but Dinan.

Keep in mind this is a low mileage, otherwise mint Z4M Coupe that I now plan to keep for at minimum a few years

Are there any options I'm overlooking? Thoughts?