Debris in no.2 cyl??

[silvertdvw]

Anyone have any idea what might have happened?? everything was freshly rebuilt with approx. 28,000 troble free kms didn't use any oil, or coolant and the egt's were closely monitored and the injectors were also freshly rebuilt. When I had the head decked they machined it with the perchambers in; could a chunk of a prechamber fallen off? there were minor cracks in the prechambers before they were machined. any advice/opinions would be greatly apperciated.

[R.O.R-2.0]

pre-chamber is twisted from original position..

head and piston are trashed..

i would say that if you knock that pre-cup out, it will have chunks missing from the edges of the part actually sitting in the head.

may not have pieces missing from the face, but i bet its coming apart. either that, or you sucked something up, like a bolt, washer, something like that, and it killed your engine..

[CRSMP5]

piece of glowplug from twisted cup???

none the less.. looks like the cup has been vibrating around aka its polished up..

[R.O.R-2.0]

look around the edge of the cup.. theres a gap between the lip of the face, and the head casting..

that head is done for.. could be broken glow plug, but i bet its a nice sized chunk of cup..

arent most glow plug tips made from ceramic or porcelain? would ceramic or porcelain cause THAT much damage? the engine i had that dropped a valve, didnt look much worse, and i never found the valve stem.. 

[silvertdvw]

glowplug is fine and I haven't even had the airfilter off in the last 5000kms so I don't think it sucked something in, I guess it must've been a piece of the prechamber. I've been hearing a slight ticking for a while now, maybe it was a small piece that's been in there for a long time?

[R.O.R-2.0]

glowplug is fine and I haven't even had the airfilter off in the last 5000kms so I don't think it sucked something in, I guess it must've been a piece of the prechamber. I've been hearing a slight ticking for a while now, maybe it was a small piece that's been in there for a long time?

 the slight ticking was the pre-chamber jumping around in the head.. removing material from its bore, and becoming more loose every time it was started/ran..

[silvertdvw]

This is whats left of the prechamber. Found this in 935racer's build thread

 "Well after that much suspense it appears that the injector was worn and leaking, to the point were it eventually was sticking open, causing enough heat to melt out the pre cup and have it fall into the piston, and then that smashing the motor"

Sounds like the same thing but I had my injectors fully rebuilt recently.

   
   

[RabbitJockey]

wow thats awful i can see the cross hatching in the other cylinder, how does the damaged cylinders bore look?

[RabbitJockey]

how did the cracks in the prechambers look prior to this?

[silvertdvw]

had the injectors pop tested and the spray pattern checked and they were good. so the problem must've been a prechamber coming loose. the prechambers all had small hairline cracks near the center. The cylinder looks alright; there were a few nicks around the top edge, but the ring wont even touch them.

[R.O.R-2.0]

This is whats left of the prechamber. Found this in 935racer's build thread

 "Well after that much suspense it appears that the injector was worn and leaking, to the point were it eventually was sticking open, causing enough heat to melt out the pre cup and have it fall into the piston, and then that smashing the motor"

Sounds like the same thing but I had my injectors fully rebuilt recently.

   
   

is the cup burned away, or cracked? i guess if it were burned away, then there wouldnt have been that much damage form a chunk of debris.

[Mark(The Miser)UK]

If money's tight, I'd just hammer the surfaces flat, sand off any flaky bits,  put in a new cup and reassemble.

[R.O.R-2.0]

If money's tight, I'd just hammer the surfaces flat, sand off any flaky bits,  put in a new cup and reassemble.

theres no way i would do that unless the new cup fit tight in the head, and i bet it wont fit tight, being that the old cup was already loose in there for lots of miles..

if the cup dont fit right, it will do the same thing again in short order..

[RabbitJockey]

my guess at how these things happen: cracks continued to grow and grow, until they were totally through the chamber, and then some fuel and air was getting in the crack as the major changes in pressure happen, so the fuel and air could slowly start eating away in between the cracks until that hunk was loose enough that it could drop the small distance to where the piston could just barely start kissing it, and eventually smashing it loose.  and making a flaky head.... honestly i don't think i'd try running that head again.  even if the precup area cleaned up decent, i just wouldn't trust it.  no reman heads are only around 500 anyways,  u'll get that much into rebuilding one.

[745 turbogreasel]

For comparison, VWOA fed this cyl a glow plug 'free of charge'.  gee, thanks guys