I'm supposed to do a cam swap on mine soon as well. From what I've read, the 3.9 cam will already be a nice boost over the 3.5 cam, and last much longer. You can also check out www.aluminumv8.com
. he carries a lot of Rover compatible parts including camshafts. If you want to stick to the factory Rover parts, I have a brand new Rover 3.9 cam and lifters that I would happily exchange for a Crower cam and lifters. Don't forget a good double-roller timing chain if your budget can support it, the factory timing chain SUCKS.
I've done a couple in the past on other engines, so here is some tidbits for you.
1. Get the proper engine assembly lube, Moly-disomethingorother. ALL speed shops will have it. Use it liberally on all the cam lobes and bearing portions. Same with the lifters. This stuff lubricates it all until the engine oil gets up to pressure. Oh, and use regular detergent oil, no synthetics for an initial cam run.
2. Make sure to prime the oil system before starting. On a rover engine, that means opening up the oil pump and filling it with vaseline. On Chevy's and Ford's, I've taken out the distributor so that I could drive the oil pump directly before starting. I've also heard that you can disconnect the ignition coil and crank the engine a bit to do the same thing. Either way, you need to get all the oil passages filled up in the cam area. If you want, try to get an oil pressure gauge mounted somewhere to keep an eye on it.
3. You need to run the engine around 20 minutes to get the wear patterns set on the lifters. Some people use specific RPM/Time charts to do it, since you do need to vary the RPM as you go. (Make sure you have enough gas :-) )
4. Go easy on the engine for about a thousand miles to let it break-in.
5. Get a buddy to be there when you start it up. While you/he runs the throttle, the other can keep an eye for leaks and problems as they occur. As soon as it turns over, check the timing IMMEDIATELY. Then, watch the oil level, coolent level and everything until you are satisfied there are no problems.