[Jim c]

Yes I have read that as well.
A mill finish alloy is also good I think it comes in 2nd to a black painted surface in the Bosch handbook.
I have scotch brighted radiators and intercoolers to get the dull mill finish.
An alloy painted black I have never tryed but would be interesting.

I have made a few radiators over the years and have come to the conclution that the alloy works more efficiantly.
Back to back I have had better results.
No more than 2 rows it is lighter It generaly will run less water and has still done the job.

I understand what you are saying about the brass but something seems to work better with the alloy in real life maybe it is in the fin pitch ,I dont have an answer to that.

Jim