Yeah, my thought was welded chambers and grind to shape

Yes! welding and grinding by someone talented, not me 😊

Jon, What's something like that worth?

I've got a P90 here collecting dust that someone has done that kind of work to. Not quite as extensive, but similar.

3 hours ago, Captain Obvious said:

Jon, What's something like that worth?

I've got a P90 here collecting dust that someone has done that kind of work to. Not quite as extensive, but similar.

quite a lot I'd think, its a good start for a 300 bhp engine. 

19 hours ago, madkaw said:

You guys haven’t even mentioned the best head yet - MN -47 . Because it wasn’t in the Z , people forget about it . It has the best all around combination for a street motor . Maybe not the best race head , but best bolt on for power with the least amount of work . Small chamber - high quench , good casting .

I also think the E88 efi (closed chamber) head should not be forgotten..

Here is my E31 flow data.  

8 hours ago, jonbill said:

quite a lot I'd think, its a good start for a 300 bhp engine. 

Here's a pic of one of the cylinders. Not as much material added as the one in your pic, but definitely a bunch added. Does this look reasonable?

My days of building up a 300 bhp motor are behind me.    

15 hours ago, moelk said:

I also think the E88 efi (closed chamber) head should not be forgotten..

Very similar but has square exhausts instead our U.S.A. round ports

1 hour ago, madkaw said:

Very similar but has square exhausts instead our U.S.A. round ports

Yes.

Mines still sitting on the shelf, would be a nice upgrade from the late us e88 head that’s on my engine now.

12 hours ago, Captain Obvious said:

Here's a pic of one of the cylinders. Not as much material added as the one in your pic, but definitely a bunch added. Does this look reasonable?

My days of building up a 300 bhp motor are behind me.    

Here's an unmodified  P90 (I think it's unmodified anyway!)

So yours has been filled in quite a lot on the left side, and maybe also around the spark plug boss (but that also could just be a big skim maybe?) 

I'm surprised there's not more of a chamfer on that infill - isn't 'unshrouding' the valves part of head porting 101? 

Yes, mine has been filled in a lot on the left, and around the spark plug as well. That's not just a shave that made the spark plug area look like that.

I was also thinking that the wall down towards the valves was too abrupt. But that could easily be sloped off a little more gradual by removing some of the infill.

By it's next owner.    

We've been using an N42 head for the past 4 years on the L28 race engines with great success. These have had extensive work done with race cams and all parts cyrotreated and REMed. CRs range from high 12s to mid 13s running on either 110 or 112. The L24 has an original BSR E31 that we duplicated for $$$.  Which is better? That's really hard to say since there are so many variables with the biggest being the driver. Dyno time (engine) is not cheap and the best chassis dyno is not close enough to play "let's swap heads to see if we can get 3 more HP".