Cracked HEAD

Post by **LukeBoorman** » Wed Nov 21, 2007 6:45 pm

I spent the weekend cleaning and stripping down my mini-sport big valve stage 3 12G940 Cylinder Head. This was fitted to my old marina 1275 engine, but after removing it due to a burnt out exhaust valve i was going to fit it to my brothers mini.

However after removing the valves and a good layer of carbon, I have found

hairline cracks

running in between the exhaust and inlet valve ports on three out of the four cylinders two at about 10mm deep and one at about 15mm. One cylinder also has two cracks going out from the exhaust valve towards the spark plug side of the head although these are not too long.

can it be used?? or can it be fixed for a sensible price or Is the head worth selling??

If not it will become the worlds heaviest doorstop / paperweight as the porting and polishing looks too good to throw it.

Thanks

Post by **MoggyTech** » Wed Nov 21, 2007 7:22 pm

Engineering engine specialists can stitch some cracks, but I doubt it would be worth it given the number of cracks you have found. Not sure how hard it will be to find a good replacement, but that would be the way to go.

Post by **Orkney** » Wed Nov 21, 2007 7:38 pm

Sounds like a scrap bin job

if it's gone like that maybe was over ported - weak points give - that or it was a shoddy chunk of metal before it was tuned (had that happen to me before and took xrays in sweden to find poor metalurgy before it was resolved).
Stitching it even if cheap would just be passing the problem on to someone else if theres no other probable cause for the failures.

Post by **flying** » Wed Nov 21, 2007 8:22 pm

i recently found the same problem on my ford....head is U/S the crack will go further than you can see,so even putting inserts wont help....afraid you need another head,thats the route i took

Post by **LukeBoorman** » Thu Nov 22, 2007 11:45 am

Thanks for the info. I will leave the current standard head on.

Luke

Post by **les** » Thu Nov 22, 2007 9:29 pm

The 940 head was a replacement for the original aeg163 head fitted to the 1275 coopers. The reason being the original cracked between the seats as the valves were so close, modding your head has put you back in this situation.

Post by **bmcecosse** » Wed Dec 05, 2007 10:52 pm

The 940 heads very rarely crack like this - unless they are seriously overheated, ie - run with no water ! Salvage the valves and the casting makes a good door stop.