4G63 Major Failure

My guess is that the engine is way to far gone to work out the originating failure.

But any insight would be great. I have put the pics in PDF with a description above each one.

This happened at Eastern Creek Raceway NSW, no warning lights or oil lights prior to the destruction.

What sort of rpm were you pulling when it failed?

There isn't apparently heat discolouration, and my thinking is a stretched rod bolt (or bolts) that may have allowed a slight relaxation of the marked bearing, which could have allowed the bearing contact and marking, before finally breaking.

If that's correct, and you can salvage the remains of the bolts, you may be able to see stretching (necking) and a cranular look at the failure point(s). A guide - https://www.onallcylinders.com/2014/03/13/diagnose-common-fastener-failures/

I was just lifting off the throttle, and don't have data, but I think this was around the 6500 mark

It looks like 2 pistons stuck in bores? Too much heat for ring gap?

Thanks Gord, for the input, the bolts are unfortunately munched and squashed and I just binned them not thinking they would tell me much, so checking the breaks are a little hard :) but makes sense what you are Suggesting.

Cyl 3 rod bolts sheared in to very different places, one sheared fairly cleanly at the nut, the other halfway done the shaft and has weird stretch marks.

Cyl 4 only found one stud, the other must of been ejected, the one that i found sheared half way up the shaft as well.

Michael, I couldn't see any marks on the bore that would indicate this, there was the obvious scores an impact damage, but couldn't see a transfer of material or heat mark on the bore, not saying it wasn't there though.

I should also mention that this was a stock factory built engine, with no mods at all. roughly 44,000 kms on it.