What do Dunnell do to their engines?
I think that they alter the tappet design and fit a differently machined cam (although the profile is supopsed to be the same). Their sump is obviously baffled and modified (wider, lower) and you get a dipstick recalibrated. You also get a bespoke ECU if ordered and they'll set the carbs up for you with correct progression drillings. You get a nice manual style folder and bits n bobs and a power curve.
Personally, I'd go for weber alpha's ECU as it seems simpler to fit, and I'd use JWhiting for all the bits that you fit to it (for reasons of local tech support). I have an all Dunnell set up. Don't forget to remove all those crossflow bits that aren't engine though as I forgot and it cost a fortune to replace.
Why diodn't Caterham fit one: I'm advised that they trialled what they asked Ford for, which was not a zetec. They asked for a part number and got it. It was actually a late twin cam 2.0 ltr from a Sierra which was too big for the 7, put out low power and was rough- wasn't a zetec.
Nigel Mills - xflow