So this is out the engine I had with a blown headgasket. Along with that it had what sounded like a big end bearing going at high rpm. The motor had been build in the backyard by a previous owner. Stripped the motor down to check them out, and this is what I found. I never seen bearings with those chunks taken out? Lack of oil maybe?
Lack of oil and/or badly fitted bearings(insufficient clearance)resulting in overheating and melting of bearing material. IMHO.
That is what I was thinking! (the clearance part) I wanted to see if anyone else was thinking along the same lines as I was.
Oil starvation, that's all the shiny stuff is. No discolourisation or from burnt metal. The shiny patches are along the wear lines and not across it nor just on the side of the bearing - indicating that the crank and journals were shaped right. Going by the pitting I would say crap or very old oil. The following has a good run down on most failures. http://www.nb-cofrisa.com/docs/web_fallos_ing.PDF
The other interesting part was the chipped part were all from the conrod top part and not the bottom.
Over loaded bearing What has happened here is the white metal has lift off the base me trial this does happen due to oil starvation. Either it has been detonating, or the driver has over speed the engine, or there has been significant low rpm knocking. What happens is the oil wedge puts such load on the shell it causes crack in the white metal, oil the is forced into the cracks then underneath the softer white metal. This is a very rare failure for a petrol engine, and is more likely in a diesel. The fact that you could tear it down and find this is testimony to the inherent strength of the vg. I call it operator error failure.
What Dave said..... read it again Low oil levels at an idle cause 'pulses' through the oil system, these pulses act like a hydraulic punch at the softer white-metal and basically blasts away the white metal. The same thing happens at high rpm with a low oil level, the oil pump struggles to supply a constant pressure of oil..... pulses again happen and they then attack the bearing, only far faster than the idle process. The engines I've seen it in before are..... V6 from a metro CBD = spent most of its life at idle at the lights and wasn't serviced at all well. Diesel Generator static plant= the generator was only started 2~3 times a year and left to idle for about an hour before being shut down (noise of the engine wasn't good for patients), it also had never had an oil change in ~20years 1936HarleyDavidson engine= converted to run a waterpump on a farm during the 2nd WW, left at low rpm for hours on end and un-serviced entirely, only topped up with sump oil up until 2001 when I snaveled the engine for a slab :rofl: interestingly enough I got 3 Harley engines from that farm, a 1926 motor that's good as a door stop and a 1939 WL motor that had suffered from a holed piston, the replacement piston was hand crafted from a lump of redgum and had a copper "hat" nailed onto the crown and large copper wire was used as rings..... tough times back then
Way forward Dave was suggesting over running or low speed knock. In the absence of the latter, I also suspect the former. Also bad or old oil unable to keep up with engine flogging. Anyway the way forward is obviously a tidy up of the crank and big end but also look at oil pump and system.
