Cylinder Head Lifespan

[garciapiano]

What is the lifespan of a 1Z/AHU cylinder head and how would one know if it has worn past its safe lifespan?

I have essentially unknown mileage on my engine (previous owner had swapped out the original cluster) and I'm not sure if there is a way to effectively measure wear of the cylinder head. I suppose one could do a leak-down test... but that's more work than I'd like to do and the car runs quite strong.

Is there the potential for catastrophic damage if the head wears too much?

 

[oilhammer]

The valve guides wear, but from an "operational" standpoint, you'd likely not really ever know this. It will start and run just fine. And this alone would not be cause to take the head off and replace the guides.

In extreme cases, the lifter bores wear to the point that the oil pressure cannot properly pump up the hydraulic lash adjuster, so the engine will tick and the lifter(s) will not spin. The only fix for this is reboring and pressing a sleeve into the lifter bore, or replacement of the head altogether.

If the engine starts and runs well, makes no unusual noises, and isn't consuming an excessive amount of oil, I would not worry about it.

 

[Franko6]

I have repaired cylinder heads with little or not appreciable wear (maintenance has a lot to do with it) on engines up to 611,000 miles. I did have to lower the cam caps and reset the cam bore clearances. But the lifter clearances were great! Of course the cam/ lifter set and valve guides were replaced. T

The same engine was at 730,000 miles when it got T-boned. So, don't know... it probably could have hit 1,000,000 miles.

We routinely repair cylinder heads with 250k- 350k. They are amazingly robust. The cylinder head wear will announce itself prior to doing anything radical. Usually a lot of ticking noises, and I agree with OilHammer... a loose lifter bore will not pump up correctly and will drop overall oil pressure. We use an aluminum sleeve that we weld into place, if a lifter bore is worn out.

 

[Mongler98]

my head on my ahu at 320K on the clock, had worn guides, valves had about 1mm of play in them from center as seated to edge of play for a total of about 2 mm of tota side play. other than that my swirles were all clogged but that's typical. can't judge my head much as it was overheated a few times and had constant gasket lift issues. the guides could have been roasted from that so..... grain of salt!