Rocker put a hole in valve cover

[Scrappydoo]

Not the first time that a mod has sidelined a rocker

[Ultramaroon]

Originally Posted by bfrank1972

I'd be more inclined to think engine temp/lack of oil pressure would be a culprit.

They all contribute to hasten the demise of an improperly manufactured part.

Inspect all of them. If they show any sign of a characteristic weakness, address that. The number of high-mileage modestly boosted stock engines in existence points to stock rocker arms being up to the task.

[Tokay444]

Originally Posted by Ultramaroon

Does it? o.0

The vacuum to which you're referring is downstream of the valve. It has to open up against that - like lifting your hand off of a shop vac hose.

Or am I missing something? Honest question.

We know the motor uses reversion at certain rpm ranges, to substitute for the lack of egr valve. That's pulling exhaust back into the cylinder. The exhaust valve opens before bottom dead centre. That's vacuum in the cylinder.

[Ultramaroon]

Originally Posted by Tokay444

We know the motor uses reversion at certain rpm ranges, to substitute for the lack of egr valve. That's pulling exhaust back into the cylinder. The exhaust valve opens before bottom dead centre. That's vacuum in the cylinder.

Are you saying at the time when the exhaust valve opens, pressure in the combustion chamber is below ambient?

[Tokay444]

I'm saying boost adds no added stress to opening the exhaust valve.
For reversion to work, pressure in the cylinder needs to be less than in the exhaust manifold. Obviously the engine doesn't run under that condition through the whole rev range. It's done with fancy cam phasing.

[Ultramaroon]

Originally Posted by Tokay444

I'm saying boost adds no added stress to opening the exhaust valve.
For reversion to work, pressure in the cylinder needs to be less than in the exhaust manifold. Obviously the engine doesn't run under that condition through the whole rev range. It's done with fancy cam phasing.

I'm lost because earlier you were discussing scavenging and then switched to reversion. I think reversion works by setting the exhaust timing really late so both intake and exhaust valves are open at the beginning of the intake stroke.

Oh, well. We agree that it doesn't really play in this failure.

[C4RBON]

At the end of the power stroke, the pressure in the cylinder is still above ambient (for Otto-cycle). To open the exhaust valve, the rocker has to push against the spring force and the pressure in the cylinder. Increasing the torque of the engine will increase the pressure in the cylinder at BDC.

Shoving 40% more air in the cylinder would reasonably result in 40% increase in cylinder pressure when the exhaust valve opens. I think there is an argument that adding the supercharger could have caused the rocker to fail.

However, I suspect the spring force is much greater than the force from the cylinder pressure. I think one of the following is more likely to have caused the failure:
- manufacturer defect (the "it was going to fail anyway" argument)
- previous damage weakening the part (some high-rpm adventurism in the past)
- poor oil, or debris in the oil

I doubt the timing of the failure is a coincidence. I know if I had just installed some new parts, I'd be hammering down a canyon road, too. I'm interested in seeing the teardown.

[Ultramaroon]

Don't forget the force required to accelerate the mass of the valve. That's a huge contributor.

[leets4uc3]

Here is a better look at my rocker. Pin didn't walk out so I'm guessing bent valve. I ordered a new engine today and plan to get the other one out this weekend.

http://imgur.com/a/2YnvU


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[Ultramaroon]

The plot thickens. Did you overrev?

[leets4uc3]

Originally Posted by Ultramaroon

The plot thickens. Did you overrev?

Nope. I was at 4k-6k revs because I was stuck behind some cars on the up. The way down I coasting pretty much. I only went half way up the mountain too. About 15 minutes up. I think i started to smell smoking oil shortly after I started to head back down.

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[Kris86]

Originally Posted by leets4uc3

Here is a better look at my rocker. Pin didn't walk out so I'm guessing bent valve. I ordered a new engine today and plan to get the other one out this weekend.

http://imgur.com/a/2YnvU


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oh wow, this is interesting.


u using stock valves and springs?

[celek]

After reading the pissing contest
In the past even in stock motors it has been an over rev and valve float spitting out rockers. Most tuned cars raise the rev limit for some dumb reason. So above the designed Stock redline the valve starts to float the rocker rattles around and spits out.
Over time you could see stress fractures like the pic above cause total failure.

Other rocker failures have seen the pin come loose and fall out but that's only 1 that I have seen.
Most failures have resulted in valve float above stock red line.
THIS engine is as light and loose as possible to make 200base HP

Combined in the failure here is Forced induction... which can cause valve float with pressure pushing against the valve head.
Keeps the valves open, pistons hulk smash valves, crush the rocker back and out of the engine.

I really would like another detailed reason for failure other than this since I have almost $12k in an engine build and like to avoid turning my money into a pile of sh!t because some companies no names mentioned won't release any information.

[leets4uc3]

Originally Posted by Kris86

oh wow, this is interesting.


u using stock valves and springs?

Yeah.

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