I have a Toyota owner Jeep. Had a blown head gasket, most likely cause it got over heated. I removed the head and had machine shop do a valve job and had the head re-surfaced, put together, set the valves to the spec's called for, no problem till I started the motor.

It made some load clacking noise, so turned it off. I checked the rockers. I found a bent push rod in number 4 cylinder. I took the head off again, back to the machine shop and they found a broken valve guide and also put in a new exhaust valve.

Back home, another new gasket set, set the valve adjustments again. All is ok till I started the engine again, then, clack noise was back again, turned it off. 

This time it was the push rod in # 3 cylinder bent. So I have to wait till the 5th of april to get it tore down again. 

I think its going to be another broken valve guide and will also need a new exhaust valve.

***What could could be the problem?*** 

I'm afraid to do this again.