I have a DX, can I put the better breathing Si head on my DX block (the Si and the DX share the same EW block).

From RPRWiki

This answer comes from the Mk1CRX discussion group on Yahoo Groups: I would definitely go for the Si head. I have done it and I was amazed. I shaved my Si head .040 to recover lost compression, but it\'s not necessary, you\'ll just have low compression. If you do shave the head, a cam gear is most beneficial, because shaving the head automatically retards cam timing and the gear will get it back to stock or preferably a bit advanced, good for mid range power. I went the dual side draft route, very simple manifold and no worries. Weber Carbs: they are unmatched in the world of carburetion, but very, expensive, and a PITA to tune and sync the first time, along with being very sensitive to dramatic weather changes. Weber makes side drafts, in several varieties. The most common [and arguably the best carb of any configuration ever made] is the DCOE. They\'re a twin carburetor design, meaning that there are two distinct throats that act independently of one another, but share the same body. They can be found with 40, 45 and 52mm throats [I think there are more, but those are the most popular, esp. the DCOE 40]. The easiest way to get more power from an engine is to allow it more air with the proper amount of fuel. For my engine, I chose twin DCOE 40 Webers [that\'s four (count\'em, 4) air horns], with a DC sports header. Mikuni\'s are nice, easily tuned, but Webers blow them out of the water if they\'re jetted even close. You can find more models and prices of Weber carbs and carb kits at: http://www.carburetion.com/