BBC Heads
 

I know this probably has been asked numerous times.Can a gen 6 head work on a gen4 block?
thanks

To the best of my knowledge a Gen VI head will work on a Gen IV motor, but a Gen IV head won't work on a Gen VI (you can go backward in years, but not forward) as cast. That said, I believe you can machine/cut/drill out the cooling passages on the Gen IV head to make them work on a Gen VI motor.

I thought it worked the other way GenVI block to GenIV heads

I don't think so... I think the Gen VI block has additional cooling passages that the Gen IV doesn't have, so you have to machine the Gen IV heads if you want to use them on the Gen VI block... I could be wrong though. I don't have much exp. with the newer blocks, everything I've done so far is all Gen IV.

I have gen VI heads on my Gen IV block and no issues to date.

Well that have involved the heads:angry-smiley-038:

And I have Mk IV heads on a Gen VI block. Think it's just Mk IV head on Gen V block that is the issue requiring a special head gasket if you try it.

Starting with a Gen VI block, you can use any head you want (Gen V and VI, Mk IV, or aftermarket). You should not put a Gen VI head on MK IV block. There is a very good chance it will leak water into the lifter valley. Some will work, most will not.
Eddie

If this were true, then you would not be able to put an aftermarket head on the Gen VI block. All of the aftermarket heads are based on MK IV.
It is the other way around.
Eddie

Yea, what Eddie said. I have mark IV heads on gen V block, works fine. I have heard not to go the other way.

thanks guys for the info