cracks in head

[bernsaudi]

I've got 2 ABY heads, both with 1 light crack going to plug per exhaust valve. Are these scrap? I want to rebuild my old ABY engine after the little scare I've had with my crank pulley keyway so should I use one or find a 7A?

[andy10v]

Workshop manual says you can re use the head as long as the cracks are less than 0.5mm, cracks in spark plug threads must not be beyond the first coil.

[Monkeymagic]

I believe most will be cracked take it to a machine shop for peace of mind.

[UrS4boy]

I've got 2 ABY heads, both with 1 light crack going to plug per exhaust valve. Are these scrap?

On page. C 15-1 of Volume 1 of the three volume C4 Bentley hard copy, regarding cracks around the AAN (and ABY and ADU) spark plug threads, they say:

"Cylinder heads with cracks between the valve seats or between the valve seat and spark plug threads may be reused without reducing service life, provided cracks do not exceed 0.5 mm (0.020 in) width or when no more than the first threads are cracked".

This same info is on page 39/93 of the AAN pdf that is available for download from the website below:

http://www.s2-audi.co.uk/workshop/aan/aan.pdf

[bernsaudi]

Thanks for digging that out, I've had them hanging around for ages thinking they may be just paperweights but there's hope yet . I'll get them tested next week in brum

[G60Rallye]

I think you will find all heads are cracked, both heads I have are. They don't tend to cause any issues and I imagine most peoples engines have cracks but they are blissfully unaware.

[bernsaudi]

Ignorance is bliss until the keyway goes on your crank pulley, then it gets twitchy I've seen some heads off vw diesels with loads of cracks in that were still working. Just out of interest in the aan doc the term service life is used. What is considered as 'service life' of one of these heads?

[popdemonic]

I have seen head with multiple cracks but still running like a train today whilst some head has one single crack but leaking the coolant through the crack.i think it depends on where the crack is.some cracks is fixable and some might not.i have seen a head with one crack running along the spark plug thread perhap 3-4mm depth.the head became trash.