If you have a Rover P5B V8 model like me, you’ll probably love the car, but it could use more power. The original P5B engine is of the 3500cc variety. The good thing when it was first released was that it had a higher compression ratio than some of the later engines, but because the heads had smaller inlet and outlet valves, it still limited power a bit. The other downside was the issue that LED fuel wasn’t available so you have to keep adding lead additives to the fuel which a lot of P5 owners know is a bit of a pain as you’re always at the gas station with a such a big engine.

My first trick was to replace the heads with heads from the Rover SD1 which with the larger valves and unleaded valve stems saved me the trouble of putting the fuel additive in each time, but I didn’t really notice much extra power. The Rover P5B is a very heavy car anyway and I guess you shouldn’t drive it fast, but I was expecting a little change in performance. I then added a Weber carb and changed the ignition to a Lumenition electronic ignition system to get rid of the old point system. This made a bit of a difference, but the performance wasn’t what I’d call a start.

So I decided to rummage through my pockets, steal the piggy bank and opt to fit the 4.6 liter engine from the latest Range Rovers. Now this engine is actually the same stock block as the 3.5 ltr in the Rover P5, so it’s really almost a direct swap. If you keep the original distributor from the P5, you must keep the same front engine cover because the oil pump teeth are different for each model. Apart from that, everything is going very well. The engine mounts line up and all the exhaust manifolds are back together as before. If you’re trying to keep your Rover looking stock, you can even use the stock rocker covers so even the insurance man won’t know the difference. Until he drove it, of course.

How do you drive? Well, between the two engines it’s like between day and night. You’ll be grinning from ear to ear for days afterward. So if you have some spare bobs and need your Rover P5 to pick up its heels and go. Your only option has to be the 4.6Ltr V8.