[Jeff Lee]

Straight from NHRA.com regarding 2008 Ford: (note the 330 CID is the 5.4L and 281 CID is 4.6L). These are all the supercharged engines. Also note both of the the 281 Supercharged engines are rated HIGHER than the 5.4L Supercharged engine.
Pistons have more compression on the 281 engines. The 281 engines have larger camshafts also. I don't believe either compression or cam lift will be significant in gain due to the supercharger. Nothing compared to the 50 CID difference.
What I haven't been able to figure out is if the 2007 Shelby 5.4L supercharged engine is rated 500 HP, then what justifies a 75 HP drop for the 2008 Cobra Jet engine? A slight difference in cam lift and compression on a SC engine does not warrant the -75 HP. It would seem one needs to be adjusted up or one needs to be adjusted down.

425 330 9.38 Supercharged EATON RF7R3Z-9K461 1.8 H/R 48.0 B,3,4
w/follower

430 281 10.0 Supercharged EATON R07060034-13-BB 2.00 H/R 48.0 A,1,3
w/follower

510 281 9.5 Supercharged EATON R07060136-13-BB 2.00 H/R 48.0 A,4,3
w/follower

Notes
1= Throttle Bore 2 @ 57mm = 2.244"
2= Alternate manifold 5R3E-9424-BB
3= Intercooled
4= Throttle Bore 2 @ 62mm = 2.441”

Cylinder Head Castings
A= RF3L3E-6040/6C064-K, RF9L3E-6090/6C064-B
B= RF7R3Z-6C064

Deck Piston
HP Disp Cl Type Height Vol Valves Cam Lift Gasket Springs


425 330 .074 Dish .118” 13.5 cc 2@1456/2@1259 413/413 .037 Beehive

430 281 .000 Dish .050” 4.8 cc 2@1340/1@1500 473/473 .037 Beehive

510 281 .000 Dish .098” 10.5 cc 2@1340/1@1500 473/473 .037 Beehive


The 2007 Shelby 5.4L supercharged:
500 330 .059 Dish .128” 13.5 cc 2@1456/2@1259 468/468 .037 Beehive