fbekholden.com

It's an old trick but one worth trying I reckon.

Try poking a length of thin lead solder wire through the plug hole in the direction of no1 inlet (the one that keeps breaking rockers) and hand rotate through full stroke. If it binds (ie the 'clearance' is less than the solder diameter) no harm done just back off and if it goes full rotation the valve isn't contacting the piston or alternately the solder may compress and show the clearance. Then increase solder diameter and repeat. Compare with unaffected cylinders too. Just don't force anything (doubt it would bend a valve but not worth the risk)

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Great idea Dave .........Ya learn something every day on this Forum ......and I like ya thinking mate its seems like the logical fault ...Fingers

The cam would have to have huge lift to contact the valves in a grey motor and unless it has huge overlap the valves should be well out of the way when the piston is at TDC.The most common cause for rocker breakage is coil bind ,get the rocker on full lift and check you have at least .040" between coils. Cheers Gary

A bit of feedback for everyone, after reassembling and inspecting for valve bind and other issues, we have determined that the rocker was shifting along the shaft towards the back of the car causing the push rod twist the rocker as it opened. I have just purchased a very good set of rockers so if it happens again I'll be putting solid bushes in. Fingers crossed it doesn't happen again though.

Hmmm... from memory, the only thing stopping the rockers shifting sideways are the springs on the shaft (that and the tightness of the busing tolerance, which you checked). Were the springs crook (compressed, soft)? I'm trying to think what would load the rockers sideways... valve stem not square ground at top?

Cheers,
Harv

Every sort this out?

So a bit of an update, the car has now done about 300 miles or so, including a return trip from Canberra to Goulburn, with out a problem. It seems the culprit was the rocker shaft itself. After replacing the whole front end of the rocker gear we haven't had any issues, touch wood. When rapcing the front assembly we paid a lot of attention to the spacing springs as the ones from the first assembly seemed fatigued and a little soft.