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+--- Thread: CM 871 Burnt Valve (/showthread.php?tid=6025)
CM 871 Burnt Valve - 2dlb - 03-31-2020
Good Morning Everyone, I hope you are all well in these times. I have a CM871 came in running rough ran insite and noticed in cylinder cutout that the truck would stall when u attempted to cut out 4,5or 6 with cylinders 123 shut off. the more i listened u could here a miss. Figured cyl 4 was the culprit pulled intake and injector and found the intake valve on 4 burnt through. theres about 500k on this motor and the crosshatching looks good i am wondering if anyone has had success with resetting the liners which im sure are gonna be lower than .014.I wouldn't even consider it under normal times and probably shouldn't now but was curious.
Thanks[attachment=6408][attachment=6409][attachment=6410][attachment=6411][attachment=6412]
RE: CM 871 Burnt Valve - Rawze - 03-31-2020
The overhaul kit is not the most expensive part. The labor + head etc. are all going to cost the same for a burnt valve. There is no fixing the head, there is no repair that will make it last.
overhaul kit, new head, start all over. complete inframe + all recommended methods mentioned on the forum here. It will pay for itself in about 200 - 300k miles when the engine is still going strong vs. having to come apart again.
The bigger queston is how did it end up like that?.
RE: CM 871 Burnt Valve - 2dlb - 03-31-2020
(03-31-2020 )Rawze Wrote: The overhaul kit is not the most expensive part. The labor + head etc. are all going to cost the same for a burnt valve. There is no fixing the head, there is no repair that will make it last.
overhaul kit, new head, start all over. complete inframe + all recommended methods mentioned on the forum here. It will pay for itself in about 200 - 300k miles when the engine is still going strong vs. having to come apart again.
The bigger queston is how did it end up like that?.
Im not sure this is one of the used trucks we picked up last fall. Any thoughts on causes, just tearing it down now. If i find any thing else i will post it.
Thanks for the reply.
RE: CM 871 Burnt Valve - Lonestar10 - 03-31-2020
Is it tuned if so is it from here? If it's tuned but not from someone here then there's your silverbullet most likely.
RE: CM 871 Burnt Valve - 2dlb - 03-31-2020
(03-31-2020 )Lonestar10 Wrote: Is it tuned if so is it from here? If it's tuned but not from someone here then there's your silverbullet most likely.No theres no tune this is completely stock, doc dpf did the Rawze egr tune up been working good all winter 2732cpl set at 450 15spd.
[attachment=6419][attachment=6420]
the first pic is cyl 1 the second is cyl 6
does any one have an idea on the residue that looks like brass flakes
RE: CM 871 Burnt Valve - Rawze - 03-31-2020
A burnt intake valve could be ...
Head is completely worn out and valves are riding too hgih in their seats. Valve finally gave way due to not enough meat to seal it properly.
ref with pics.: http://rawze.com/forums/showthread.php?tid=1106&pid=9466#pid9466
Could be chunk of hardened carbon, or some other foreign material (metal frag from a turbine of previously failed turbo, etc.) made its way into the valve seat and cracked the valve,.. eventually resulting in a burnt valve.
Could also be from the sudden inrush of -20 degree-C temps (dead of winter) at the top of a mountain, engine under full load, cylinders already very hot, jake brake set to 0 delay + it set on high, engine transitioning form full throttle to full engine brake too quickly in extreme conditions, cracking/weakening the valve, then eventually it burning through several months later.
Just some generalized guessing there.
RE: CM 871 Burnt Valve - 2dlb - 04-02-2020
Ok Heads off. It looks like something that affected the rear 3 cylinders im guessing, i attached some pictures if anyone has any thoughts im open. Noticed cyl 123 were looking not bad 456 look wetter. [attachment=6427][attachment=6428][attachment=6432][attachment=6430][attachment=6431]cylinders are 12456 couldnt get all 6 on
RE: CM 871 Burnt Valve - 2dlb - 04-02-2020
ill try and post some cyl [attachment=6433][attachment=6434][attachment=6435]
These are cyl's 1 4 and 5
RE: CM 871 Burnt Valve - Rawze - 04-02-2020
from looking at the pics, hard to tell, but looks like some of those valve were riding really high in their seats. Maybe looks like possibly head was worn slap out?.