[killerkaw]

ok, my 99 Discovery 2 is running great. so I think I'm about to change all that.

has anybody done any head work to these motors in an attempt to raise compression ratio to around 10.5 or so? how much horsepower and torque can the transmission and transfer case reasonably withstand?

 

[Disco Mike]

Do yourself a favor a leave your engine alone, it wasn't made for speed up low end torque. The drive train, specifically the spider gears and tranny can't handle the extra power even.

 

[Plov]

Not to disagree with Mike but these engine can make good power. The Rover V8 was the cornerstone of the British sports car and Kit car industry for a long time. The ZF trans and LT230 Transfer Case can certainly cope with more Horsepower than the Disco will ever put through them. The Diff's and driveshafts, Not so much. RPI, ACR and Turner All offer higher output engines and various upgraded components. The one thing i would caution about it to keep in mind how you use your Disco. You can spend a small fortune squeezing extra HP out of the engine and then never use it. Touque's is what you need. Max power tends to come high in the rev range, speed limits and the autobox won't keep you high on revs. The Disco works best off road at low speeds when torque is king. Unless you want to boast about your dyno numbers i wouldn't bother trying to tune for HP. Get a better CAM that will give a few more torques and save the rest of your money for something else. Just my opinion.

 

[Disco Mike]

The ZF 22 tranny in the early D2's with a 4.0 engine had to be replaced with a ZF 24 for the 4.6 engine just a mere 20 plus more horsepower, trust me Rover wouldn't have up graded the tranny just for the hell of it.

 

[Plov]

without looking to start an argument and i certainly wasn't there at the time but I would suspect the change in 03 was more to do with ZF looking to end production of the old unit and Land Rover looking to consolidate on the number of different supplied items. The ZF4HP22 was used in many applications including Porsche, Jaguar, BMW and Maserati and can take some punishment.
But to agree with Mike and refer back to the original post, if your looking to add power you will need to review the rest of the drive train to see where it will break.