hi lads just thinking wots the minimum size you would go on a Cosworth YB head when planning on going to 500 BHP

 

https://passionford.com/forum/technical-essay-archives/42723-minimum-cossie-head-thickness.html

 

I'd want it atleast 138.6mm with 500bhp.

Does anyone know if it's possible/fees-able to have a head fully TIG welded and skimmed back to its original height?

 

Hell no... but one of the breakers do this and pass them off as unskimmed.

 

 

Wtf is that

 

If it's alright to weld corroded/damaged heads why can't you weld the full face if its stress releived after?

 

Even if done correctly would you run the risk when you can buy a new head on a 10k plus engine build....

You are pairing different metals and although ok for say small repairs i would not advise a repair in the combustion area.

Also different metals expand and contract at different rates and the cossie head is no different with 17 thou of expansion during running. Hence the sealing issues with head gaskets against a cast iron block. This is why imo the alloy blocked engine is a better way to go.

 

That's the only problem the new heads are 4K+

Would you be mixing different metals though as the welding rods would be aluminium aswell?

 

You would never get the same properties in welding rods.
Don't forget the head would need to be heated to a given temp evenly then welded then carefully allowed to cool evenly to avoid cracking as the head and alloy filler rod will cool at different rates.

Good as a water jacket repair. But just think about that pic if one of those valve seats fall out......

Anyway back to the original op's question.

 

Its not so much the depth of the head from my understanding, but the depth of the valve seats, as the heads get skimmed there is less metal holding them in and they become exposed and liable to fall out!

Compression ratio can be managed in a thinner than 138.6mm head by reducing piston height, thicker gasket etc

The other factor is softening of the aluminium of the head rather than the actual thickness, if its gone too soft the gasket beds into it and you also loose torque on the head bolts as a result.

As old decent heads become rarer then solutions will be found to refurbish them no doubt.

Also new castings are now available, costly but at least you can transfer all the guts of a damaged head into one of those and start again

 

Do you mean the smith and jones new heads? You don't have to use them with the alloy block.

I dont know if the new s n j heads work with a standard iron block? Seeing that's the bit Ian needs. If his head isn't thick enough then he has the gamble of finding a second hand head that is genuine and the porting it.