Hello, as part of a top end overhaul I am putting a 3.9 camshaft into my 3.5 EFI to gain a few horses.
Are there any other mods I need to make at the same time to make best use of this camshaft, i.e ignition update or timing?
While your there, replace the lifters and also the timing chain with a duplex one. Chances are the old one is possibly stretched. If you do go the duplex you will need to grind a small amount of the inside of the timing cover to allow for the thicker sprocket and chain set.
The RPI website list this option as a 'mild cam kit' with a 10bhp possible gain.
As I need to change the cam I thought it would be a sensible mod.
I would like to know if the ignition 'mapping' ECU needs to be changed for the 3.9 version as well or if the cam change will work fine on its own.
RPI sell the kit with a duplex chain kit, followers, gaskets and timing cover seal.
I'm 99% sure that the Land Rover cams used in the 3.5 and 3.9 are the same for both lift and duration. Chances are your old 3.5 cam is worn anyway, so it makes little difference, you'll see some performance improvement, but probably no more than if you had used the 3.5 cam.
The duplex chain is stronger and the steel sprocket sold both "others" is better than the diecast sprocket with synthetic tooth sector, but, here, again you won't gain HP from this mod, if anything, just reliability. The diecast sprockets are frequently cracked at the keyway, when inspected upon removal.