Here's a drawing some may find useful. It contains porting data for the 12v 3liter head with 46mm intake valves and reshaped std.size exhaust valves, both with 8mm stems. Flow is 120/92cfm in/ex (std head has 105/80cfm) at 13mm lift and 10" vacuum. As a general idea, you follow the dotted lines. You don't remove any material from the port floor at all. Numbers shown with a slash are std/ported dimensions. Where one number is shown there is no change. Dots are dimensions perpendicular to the page. Dots on lines mean same size. Just take this info at face value, I don't want to get into any heated arguments!
This post may also help Greg get some peace of mind!
Jim K.

exelent
Jim do you have any velocity profiles too ?
btw this is good example why v6 have more potential tnah nord and even TS, port geometry is way better

Even compared to the TS? I just assumed from the pistons shape of the TS, that it had better port angles than the V6 12V. That is quite surprising (for someone like me of course ).

I'm very tempted to re-do a set of 12V heads, but I think it's just not wise to spend that much money on the 12V anymore. I've disassembled the 24V and the new 12V cams on their way here is my last upgrade for the 12V.

Thats all the available info. Nothing else will be made available.As for the TS vs 3liter (both big-valve) see the diagram below. Note that the TS has a 47.5mm valve not 46.
Btw, I'll be offline until the 23rd.
Jim K.

Thanks for sharing that Jim. Z dont give up on that 12v because most of us here are going back to 12v 3.0 L for racing( starting to race in another series with another car). There is one 12v 3.0l carbereuter which is stronger than my 24v race car. As Jim leaks info we copy. Whats size intake runners are best for that set up? or should we just wait for the book.

basic rules are: port entry 85% of valve d runner entry not smaller than valve window at max lift
some fast calcs for 44mm valve at 12 lift runner entry 46mm tapper to port entry 37.5
but this works with proper head working and matched cams

Best for 3liters are bored std runners to 39mm. For 3.5liters and up you can use the huge ones. Also depends on rpm range. For 3liter up to ~7200, stay with 39mm.
Jim K.

Jim, I take it the same porting method applies to the 2.5 heads?, all be it smaller valves and port dimensions in the first place obviously. i.e. the same percentage increase in the port dimesions, in the same locations on the inlet and exhaust ports, but applicable to the 2.5 dimensions?

You could say that, except that the 2.5 exhaust ports still fan out to 34mm. I would like to see the 2.5 with a 43-44mm intake valve though. In the near future, I will post wall thickness at different points for the 2.5.
Jim K.

many thanks Jim. Really looking forward to that book