Valve train failure...anybody ever encounter this

[Dueller]

3.2 carrera....developed sudden miss. Heard valve train noise like a seriously loose valve. Pull valve covers...on #1 exhust the retainer fell out in three pieces. But I noticed the cap on top of spring had split all the way thru in one side. Valve is obviously bent...likely hit the piston. Just wondered what might have failed first....retainer or cap. Rocker arm appears undamaged.


Back into a freshly rebuilt motor....sigh

[cgarr]

I have seen top spring retainers with cracks before but not one that has failed.

[Tippy]

Craig, you found all of my retainers cracked.

I owe you an analysis now this is brought up.

[Dueller]

Here's what I got....cracked cleaar thru. The three small pieces are the clip that goes on valve

[Walt Fricke]

The clip is usually called the "keeper." While the hat is called the retainer, as you have called it.

Hard to imagine a keeper breaking unless the retainer started failing first, allowing the keeper to assume an unnatural position. If a keeper did start failing all on its own, I'd expect that you'd see unusual wear on the grooves in the valve stem. Whereas I'd expect failure of the retainer to result in failure of the system so quickly that the stem grooves might not have had time to fret.

Look on the bright side - you were lucky. A valve falling into the cylinder can easily lead to destroying the head, piston, rod, cylinder, case, oil pump, intermediateshaft, and maybe more.

I once had your kind of luck. The tip of a VW valve pulled off, allowing the valve to fall down. Luckily the piston smacked it up into the head again, but with a bend in the valve stem. The bend bound in the guide, which prevented the valve from moving further. Having no better option, I raced the car through half of Mexico that way on 3 cylinders, and then 1200 miles back home to Colorado as well.

It would be interesting to know why retainers fail, though. I don't think it is common (which is good). I've replaced titanium retainers on race motors because the underside of the retainer showed scoring from the end of the outer spring. I haven't noticed anything similar on stock steel retainers, but perhaps that can happen and create a stress riser?

[Dueller]

Thanks for your input, Walt. Did exactly as you said....keeper and/or retainer/hat failed, piston smcked it and bent valve so as to not cause catastrophic damage....at least as far as we can see with a scope. Piston crown does not appear hurt. And the valve is stuck tight in the guide. I did notice the hat had a slight ding at the point of fracture. Don't know if the keeper failed and when it came apart the rocker dinged it or vice versa.

Rocker arm appears fine.

Engine drop party at my house!

[Dueller]