Broke a valve during the major. Yikes!

How long had it been since the last service?


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what do you understand under "cracked belt"?
cracked = broken/torn?

 

This sounds very 'unusual' and frankly, makes me question the veracity and/or competence of your tech.

Can you add more details? Photos?

I would not like to think(?) that you are being scammed.

Cheers,
Vincenzo

 

Not really. Know of it happening a number of times over the years.

 

So, you are going to replace all 24 with ss, right. Hey, it's better to have it break with the engine dormant than spinning at 6500 rpm.

If you are going to drive the car, do the diff upgrade now also and just enjoy the car for many years to come.

 

How?

During removal?

While refacing?

Cheers,
Vincenzo

 

Sorry to hear... Keep us posted on progress and cost... Burning 3 valves suggests the valves were mid gapped for a long time...

How many miles on the car? Years since last service? How was it stored?

Anectdotally, mine had 10 years and 6000m since the last major. Belts, bearings, water pump seal looked like new. Water hoses looked like new, soft... Fuel lines looked ancient...

Everything was replaced again this time around...

But it surprises me there are such differences in how these cars age... I wonder if garage storage and temp make the difference...

 

Good point and it is worth noting that over time, valve clearance shrinks.

Too tight = burned valve

When setting clearance and the shim selections seem either a bit too tight, or a bit too loose - then go with 'loose'.

Cheers,
Vincenzo
PS: for the life of me, I still can't see how a 'service' can break a valve.

 

That was an autocorrect...

Was supposed to say mis-gapped...

 

I've had sodium-filled exhaust valves break during disassembly. An accident waiting to happen.
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Based on your pic, the break occurred long before disassembly. Only the bright area of the breakage cross section was relatively recent. It suggests that the engine had bent its valves and was subsequently stored for a long period of time before it was later disassembled. IMO, the disassembly did not cause the break, but did allow the 'discovery'.

Thoughts?

Cheers...

 

so as I understand you the belts have been still working fine?
only damaged a little but not broken?
if so then it is nearly impossible that a valve stem will be broken because of doing a service. there must be a failure before already
burned valves you only may get when the valve clearance is too small, the engine is running hot and then only the exhaust valve.
the intake valve may be burned only when the mixture is too lean and the engine is turbo charged.don´t ask me why I know

 

Lots of cases of those POS valves breaking during the adjustment.

Its quite simple, if you don't like broken valves get the sodium valves out.

 

Did all Boxers, TR, and 512TR have sodium filled valves?

 

How does a valve break during an adjustment?!

That valve is being beat to death at high velocity slamming against the head at 6000 rpm under 1000 degree temps and it doesn't break? Rather, it chose to let go when you are gently depressing the shim?!

I believe it, but gasp at the physics of it...

What is the mechanism that causes it?

 

Maybe it's just good luck.

 

The cavity for the sodium looks as if it is off-center in the valve stem. Is that production tolerance? Just ask Rolls Royce about their mishap with the A380 engines (Qantas) how that works out for material strength and likelihood of breakage.

One question, has anyone ever measured that cavity diameter of new vs used valves? Is there any erosion of the steel inside the cavity, dissolving/amalgamating into the mix with sodium over time? Not that it matters much, as it quite clearly is a failed concept with regards to longevity.

 

No one else was dumb enough to use 8mm sodium filled stems.

 

Cams don't slam valves, people do.

 

Yes, no, no.