This is correct, the side not showing is touching.
What could cause this in an otherwise healthy engine?
CK5
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Help diagnose engine problem...
- Thread starter Keitha
- Start date
This is correct, the side not showing is touching.
What could cause this in an otherwise healthy engine?
At least I know that the O2 and my computer are not lying to me. I have been datalogging a lot and getting ready to program my own PROM. I am only running about 12psi fuel pressure (unless my guage is bad) and the Holley TBI. I would have thought that it could take a higher fuel pressure, but it clearly is rich.
thanks again for all the help.
A bent valve can only happen from the valve hitting the piston. If someone was adjusting the valves with the engine running and started tightening the rocker nut too quickly the valve can hit the piston since the lifter can't compensate as quickly as you tightened the valve.
I guess this looks like where the valve and piston met.
I still don't get it. There is defenite evidence of an exhaust leak that was the ticking I heard. What could cause the valve to do this after 2,000 miles? Could it have barely been touching and then for whatever reason it just hit harder and bent? Could too tight a rocker adjustment cause this?
I still don't get it. There is defenite evidence of an exhaust leak that was the ticking I heard. What could cause the valve to do this after 2,000 miles? Could it have barely been touching and then for whatever reason it just hit harder and bent? Could too tight a rocker adjustment cause this?
Slapperbar
Retired Navy NDT Examiner
#3 is not the only hole with valvetrain geometry problems. #5 is starting to hit on both in and out.
Too tight on the adjustment could cause it but it would have happened immediately. My guess is that the valve stem got hot enough to gall the valve stem in the guide and stick open then the piston hit the valve bending it.
What makes you say that?
There are several things that could cause this. Since we can't be there to inspect things ourselves, we need to consider this logically.
First of all, the valve is bent because it hit the piston. Almost a given.
The only way the valve can hit the piston is because it was open when the piston came up.
Its not a timing chain issue, because all the valves would show signs. Its probably not an isolated bad valve setup, because at least one other cylinder shows signs of contact.
So, what could cause a valve to stay open?
Either it jammed open or was held open.
Jammed open should be either a too tight valve stem bushing, or too much heat.
I would expect a valve stem bushing to show up sooner than 2K.
Heat, you would think you would have noticed. But, I have an idea.
But, first, lets consider held open.
Adjusted too tight, unlikely. Again should have showed up sooner.
That only leaves something wrong in the valve train.
Was there plenty of oil under the valve covers? A plugged pushrod, or some other reason for too little oil might have caused the rocker arm to seize. Does it rock freely?
Failing that, if the valve train is free, then the only thing I could think of that could have held it open was a lifter pumping up too far.
I'm not sure what would cause that in a low revving engine unless there was something plugging the drain hole in the lifter.
If you can get the lifter out for that valve, you might check and see if it will depress and if there is something plugging the hole.
Getting back to heat:
Did the engine seem to be running cool? You said that you thought it had never seen 190.
The temperature sending unit is in that head.
Any chance some of the cooling passages were blocked? Wrong or improperly installed head gasket say?
If the cooling passages were blocked and the sending unit was sitting in air, it would read cooler and the engine would stay in cool mode causing it to run rich.
While the rest of the head ran hotter and hotter.
I know that is stretching things, but frankly this whole thing seems unlikely. An engine that had not run hot, with that many miles on it, having at least one and apparently more valves hitting the pistons is just wrong.
Anyone see anything I missed?
First of all, the valve is bent because it hit the piston. Almost a given.
The only way the valve can hit the piston is because it was open when the piston came up.
Its not a timing chain issue, because all the valves would show signs. Its probably not an isolated bad valve setup, because at least one other cylinder shows signs of contact.
So, what could cause a valve to stay open?
Either it jammed open or was held open.
Jammed open should be either a too tight valve stem bushing, or too much heat.
I would expect a valve stem bushing to show up sooner than 2K.
Heat, you would think you would have noticed. But, I have an idea.
But, first, lets consider held open.
Adjusted too tight, unlikely. Again should have showed up sooner.
That only leaves something wrong in the valve train.
Was there plenty of oil under the valve covers? A plugged pushrod, or some other reason for too little oil might have caused the rocker arm to seize. Does it rock freely?
Failing that, if the valve train is free, then the only thing I could think of that could have held it open was a lifter pumping up too far.
I'm not sure what would cause that in a low revving engine unless there was something plugging the drain hole in the lifter.
If you can get the lifter out for that valve, you might check and see if it will depress and if there is something plugging the hole.
Getting back to heat:
Did the engine seem to be running cool? You said that you thought it had never seen 190.
The temperature sending unit is in that head.
Any chance some of the cooling passages were blocked? Wrong or improperly installed head gasket say?
If the cooling passages were blocked and the sending unit was sitting in air, it would read cooler and the engine would stay in cool mode causing it to run rich.
While the rest of the head ran hotter and hotter.
I know that is stretching things, but frankly this whole thing seems unlikely. An engine that had not run hot, with that many miles on it, having at least one and apparently more valves hitting the pistons is just wrong.
Anyone see anything I missed?
Slapperbar
Retired Navy NDT Examiner
Well... maybe not geometry but timing, because after further investigation #1 is hitting too. I say this because these pistons DON'T have valve reliefs. Except where the valve has already smacked the snot outta the piston. #1 has no valve reliefs except where the exhaust valve has started to hit it.
He is using KB pistons and they DO have a valve relief, they are not like a factory piston which has 4 valve reliefs. The reliefs are a single relief with extra relief in the exhaust area.
smalltruckbigcid
1/2 ton status
Where was the intial timing on the timing chain set? Straight up advanced or retarded?
I don't know. I will talk to the engine builder tomorrow or Tuesday and find out.
Your good, They are Keith Black pistons. I will clean them up and check out the exhaust relief areas.
Slapperbar
Retired Navy NDT Examiner
Well I stand corrected. #5 still has issues thou.
Over rev!!!!
People are usually really good at what they do for a living.
I'm going to bet that the valve has a galled stem and that is caused from extreme heat (doesn't mean the truck overheated) extreme heat can be cause by other things in a single cylinder.
More pics...
Cleaned up pistons #3 & #5
#5 looks OK to me
Cleaned up pistons #3 & #5
#5 looks OK to me
Slapperbar
Retired Navy NDT Examiner
Hmmmm... Must've just been in the carbon.
I got the head to my engine builder. The valve was gaulled. We pulled the other valves and they all had signs of gaulling. There was also a LOT of carbon build up. The engine builder thinks that it was running so rich that the unburnt fuel in the exhaust washed out the oil from the guides. Does this theory sound legit?
For what it's worth the engine builder is well known very experianced. He has a well equiped shop and has actually written many full books on engine machining and shop manules on the various machine tools. John Edwards of R&D machine shop in Costa Mesa, CA. http://www.engine-machining.com/
I know that it was running very rich from my early efforts to tune the motor. I have been recording BLM's in the low 100 range (100-105) across the board. I have got to figure out what fuel injectors I have in my Holley TBI unit as I am only running about 12psi into my 383.
For what it's worth the engine builder is well known very experianced. He has a well equiped shop and has actually written many full books on engine machining and shop manules on the various machine tools. John Edwards of R&D machine shop in Costa Mesa, CA. http://www.engine-machining.com/
I know that it was running very rich from my early efforts to tune the motor. I have been recording BLM's in the low 100 range (100-105) across the board. I have got to figure out what fuel injectors I have in my Holley TBI unit as I am only running about 12psi into my 383.
Those are some rusty water jackets, was that your motor you had rebuilt? Is there a helicoil in a head bolt? You are goint to pull the entire engine and built it properly this time aren't you?
