Worn rocker arms M20B20

[sgaites]

So I stripped the head of my 320 today, to find that the zero compression on cylinder 3 was caused by a snapped intake rocker arm.

I was thinking I should replace them all regardless...

The wearing on number 2 & 3 rockers (L) is odd compared to the others (R)



The rest are smooth, but there is a definite 'step' on 2 & 3. This isn't evident on the exhaust side.

Any thoughts on what could have caused this ?

Thanks

[kam-325i]

That is caused by the hardfacing being removed or not hard enough when they were produced.

[clipper]

Blimey, never seen wear like that on a rocker. It's all in the same place, as if the valves have never been adjusted?

Worst I saw was on a Kawasaki GPz600 which had been over-reved in top gear for about 10 miles up the M4 until the cams ripped the threads out of all the journals. The surfaces were corrugated.
That's how I learned what the redline really is there for.....

[johnl320]

Lots of deposits on the rockers, engine has probably missed several oil changes in its life. Looks like blocked oilways have led to some of the rockers suffering from lack of lube, what is the cam like?

[sgaites]

The cam isn't looking too bad - mirror finish on all lobes, no pitting. However the no.3 intake lobe (corresponding to the broken rocker) is a lot more worn than the others, can catch the lip with my fingernail.

Just to give you an idea of the state of the rest of the head...

[johnl320]

Ooo nasty, that spray bar is probably very blocked, must have sounded like a bag of spanners before it went pop