Reply to "Dropped a valve..."

Two possibilities. First, the keeper was chipped during assembly, resulting
in a loose fit that wore against the valve until the valve slipped out and
smacked by the piston. The resultant motion knocked the roller rocker tip
off. Second, the tip of roller rocker fell off but the rocker kept pushing
on the retainer until it wore enough for the valve to slip out. Not sure
which it was but neither of those implicate the valves.

> Second, if this is a hydraulic roller lifter camshaft, that right there is
> part of the problem. I suspect what happens is that even though that profile
> is "represented" as "streetable", it has a timing pattern that is not
> cushioning the closing of the valves.
>
> My personal opinion is that you just can't build these engines with
> components like AFTERMARKET roller camshafts and expect them to have a
> longevity significantly longer then an engine built to run in Pro Stock
> drag racing.

Hydraulic roller camshafts have lower seat accelerations than a performance
solid flat tappet and usually have a lower ramp rate. For instance, an
OEM flat tappet cam has a ramp rate of around 2. The hydraulic roller
I spec'd for Mike Drew's 408C is around 3 but the solid flat tappet cam
in Mid Engine Mike McDougal's 393C is right at 5. I don't know what lobes
MME uses but a hydraulic roller with a very large ramp rate would not
rev well in an engine like a Cleveland (large rocker ratio and heavy valves).
One issue rollers can have is if the springs have insufficient seat pressure,
the valves can bounce off the seat. Solid rollers are a completely different
animal. Some of those can be quite aggressive but there are also more gentle
street lobes available.

> Most likely that is why the other valves are showing signs of "over reving".

Do the other valves show a wear pattern like the failed valve?

The big question is where is the debris from this mess. Did it find its way
to the bearings? I'd disassemble the engine and check all the bearings. If
you run it the way it is, you risk scoring the crank or a piece of debris
clogging a pushrod or oil passage which can lead to more catastrophic results.

Dan Jones