345kw of V8 Windsor Power
Join Date: Jul 2001
The 220kw XR8 heads are modified cast iron GT40P's. Thay have larger stainless steel high swirl 1.90" and 1.60" valves (up from 1.84" & 1.54" from memory), some slight porting in the exhaust and intake runners and are shaved down to 58cc to increase compression. With those mods they flow nearly 20cfm per intake runner more than the stock GT40P's, and much more on the exhaust (cant remember the figures though). The T-series got aluminium GT40P heads which obviously flow really quite well straight out of the box and are lighter than the cast version, but are also much more expensive.