We recently built an LS1 engine that had some specific requirement. The engine was to be installed in an AWD vehicle with an automatic transmission and had to idle as smooth as a pussycat, be very drivable, and produce 600hp. What we came up with is a 427ci engine with our TPiS stage 3 heads using the 2.100" hollow stem valves, our LS6 modified intake manifold with our billet oval throttle body, and our 1-3/4 primary tube headers. We selected our ZL15 camshaft with 114 degree lobe seperation to control valve events. This combination produced a well behaved engine with excellent idle quality. This engine is incrediably streetable and has power on tap, ready to be used at driver's will. The attached picture is the actual dyno sheet, straight from the dyno printer.