4 replies to this topic

[Keith Grendahl]

1275 A, 12G1316 Austin America Smog Head

As you can see I burned an exhaust valve in cylinder 2. The other 7 valves all look fine, just need lapping.
I had hardened seats pressed in and multi-angle grind done about 4,000 miles ago. Does the seat look like it can be ground to fit a new valve or should I get have another seat in standby? I'll need to order the valve and am wondering if I should order another seat at the same time?

I assume I had that tappet set incorrectly or a bit of debris got trapped in the valve. Any other theories?

Keith

 seat.jpg   141.75K   38 downloads
 Valve.jpg   57.29K   32 downloads

Edited by Keith Grendahl, 06 March 2012 - 12:38 AM.

[tiger99]

Or mixture too weak, so combustion temperature is too high. That used to be the cause many years ago, but I think valves are made from better material now, so it is rare.

[Keith Grendahl]

The common theme so far is that it was more common years ago. The engine is from the late 60's or early 70's. I ordered a new valve, it will be interesting to compare it to the older valves this engine has. Maybe I should have ordered 4 new valves.

[Cooperman]

A light 'kiss' with a seat cutter should clean it up OK. Then just lap in a new valve and 'jobsagoodun'.

[bmcecosse]

That seat will be fine - new valve - and set the exhaust valve gaps to 15 thou in future - and check/reset regularly.....