I'm doing the infamous Valley Hose on my '07 XJR. Also, servicing the (M112) SC and other stuff along the way. And, got to wondering: where did that extra ('07 - '09 4.2L XKR) 20 HP come from?

(My thought is dual air filter intake system; maybe freer exhaust as well?)

...still looking for a pristine XKR coupe...

 

weight perhaps 4k lbs vs 3.7k?

 

Ummmm, weight would affect acceleration, not horsepower....

Various small tweaks including larger crank pulley, dual intakes and VVT VCT AJ33S vs. AJ34S

 

Thanks JA

The SC XJ models X356 (late '06 - '07 in USA) and X358 ('08 - '09 USA) do use the 400HP VVT SC engine (AJ34S, I believe). Earlier X350's use the 390HP AJ33S

Didn't realize the early XKR's use more SC overdrive (larger crank pulley). Imagine they need LSD even more than the XJR does. I see you added this to your '08...
Appreciate the info!