I've always wondered where the 4500 RPM limit "rumor" about GM's HEI module came from and finally found the source, in a book David Vizard authored called "How to Build Max-Performance Chevy Small-Blocks on a Budget". The relevant pages are actually available on the internet - [h=1][/h] How to Build Max-Performance Chevy Small-Blocks on a Budget - David Vizard - Google Books I was a little disappointed after reading all of the the various things that Vizard has written. In the end it seems l