i want to drill the exhaust manifold studs in my zetec turbo head and am wondering how deep i can drill BEFORE i go into oilways? anyhelp appreciated, cheers

 

just drill as deep as the studs need.
You WILL inevitably break out into oil return channels, don't worry about it, there is no pressure, just return drains, make sure you clean everything out properly afterwards and use oil resistant sealant on the stud threads when you fit them.

 

ok but ive heard people say they dont drill through?

 

the wall thickness isn't sufficient in some of the positions that the studs need to go to not drill "through" - maybe 8mm or so thick. Thick enough to form a decent thread, but certainly not to avoid breaking through.

http://www.rsrich.force9.co.uk/zetec-turbo/Engine.htm

you can see in this picture how thick the casting is in the new thread at the right hand side of the picture:

 

r sayin 8mm is my safe bet? cheers

 

nope, I'm saying there is only 8mm or so thickness in places so you have to break through. Don't worry about it, on that one I did all the top 4 holes break out into oil returns and it really isn't a problem, we didnt't get any issues with oil leaking past the studs.

 

i think il just go for it and see how it ends up, should be good, ive done all my oil returns etc in block so its slowly coming along