Defining the head type without using the casting numbers

[Streaky]

I put this up yesterday as my first post but for some reason it's dissapeared

Anyhow.
How can I tell the difference between 3.9 heads, 4.0 heads & 4.6 heads without reffering to the casting numbers?

What problems can we foresee if 3.9 heads are used on a 4.6 block, crank and pistons?
Cam is 3.9 standard.
ECU is a Mark Adams Tornado.

Thx all.

S.

[katanaman]

heads have been posted about hundreds of times so please have a good look round the forum for detailed information. In short though 3.9 heads have three rows of head bolts while 4 and 4.6 only have two rows. 4 and 4.6 heads also have smaller combustion chambers. Any head can be used on any engine but to keep the compression ratio the same you need to match the gasket to them, 4.6 comp gasket and 3.9 tin gasket.