hard to tell from the pictures, but some of those retainers look a bit off.

 

This is beginning to sound like the spark plug tsb or some kind of oil jet or oil starvation problem. OP: What is your engine serial #?

 

Spark plugs were stock NGKs. I have pictures of the broken one at the beginning of this thread. Unfortunately I don't know how tight they were, as I was not there when they took it apart. Still, it's an old car, and I'm the second owner. I imagine spark plug TSB would have been done....

 

Exhaust springs, with the broken valve clearly sitting lower












Click on thumbnail












Good cylinder closeup






Failed valve retainer


Other exhaust valve from destroyed cylinder


That's as far as I got taking it apart.

I'm not seeing any evidence of anything. No oil burning, no detonation, no overrev, no nothing....just a simple valve break under normal operating conditions, and the subsequent chain of events.

That's my untrained eye though. Maybe someone else will see something more in these pics? I do have more, and of higher resolution. I can also take more, of other cylinders, if people want me to zoom in anywhere, look at anything, do anything.

Also, does anybody know how to tell if the valves are original Honda parts? I'm hoping maybe someone has previously messed with the engine...

 

Impressive pictures!


How about: a seized valve guide?
That could explain the holding back to redline the first time you do that.
Maybe the guide woke-up fast enough to not let the valve hit the piston?
Until it didn't.

That said:
In the last picture, with the bend valves, it could show that a valve doesn't break when hit by the piston, it bends.
It does look like the valve disk just sheared off the stem.
(I don't know if those are the proper technical terms for it)
That stem is still reasonably straight.

 

The exhaust valves stucked in the guides. This is a problem that seems to have all engines before MY04. Looks as if Honda changed the valve guides after that.
I spotted 4 such cases in Germany. The clearance of the exhaust valves in the guides was up to 1mm! If the gap is so large, Oil or Exhaust Debris can get in between the Valve Stem and the Guide. This is burnt (Exhaust Valve) and the Valve can stuck.
If this is the case the engine power decreases until the valve comes loose and everything will work as normal. But there comes a point where the valve doesn't come free and then the upcoming piston does the rest.

 

That retainer didn't fail. retainers have nothing to do with what happened to your engine.

What happened is to be determined, but retainers have 100% nothing to do with it.

 

Right...I knew I should have renamed that, what I meant when I wrote "Failed valve retainer" was "Retainer of the failed valve".

Interesting point with the "stuck" exhaust valves. Can anybody else confirm that this happens? This is the first I hear of anything like this...I mean, that's some large forces that need to be involved in order to get a valve to stick.

The part where "engine power decreases until the valve comes loose and everything will work as normal" seems very familiar to me...but wouldn't a stuck valve result in immediate damage?

 

No, immediate failure doesn't always have to be. It's the Exhaust Valve. It has more clearance to the Top of the piston as the intake valve (which is also larger).
And I stay to my post: I have had more than usual cases where the valves had to much clearance in the guide.
Try the other valves that are not destroyed. When the valve springs are off you can feel how loose the valves are in their guides...

 

the motor had a bent valve that eventually broke.

probably something left over from the previous owner if you never over reved it. Stock valves are good at bending and not breaking for a long time.

valves dont stick in the guides.. not stock valves in stock guides anyway.