I'm no Cossie expert, but what I do know I learned from this book: "How to Power Tune Ford Sohc 4-Cylinder Engines" by Des Hammill. In Chapter 14 he goes into a fair amount of detail about the YB, including what changes are necessary to run the normally turbocharged engine as a naturally aspirated one. To get a feel for the level of information it provides you can preview some of the book here:
http://books.google.com.a...page&q&f=false Amazon (US and UK) don't have it instock, but try the Pitstop Bookshop in Perth (
http://www.pitstop.net.au). Their search engine fails to list anything by the author, but as I saw one of his books in there just last week, I'd say it's a glitch in their system, so call them and ask.
There's also this article:
http://www.classicfordmag...ed-cosworth-yb-engine/ Good luck.