Hi all

I have a 51 plate Westminster which is in many ways a brilliant car. The only shame is they fitted it with the 4.0 block... should have been a 4.6!

The engine at the moment, apart from a rocker gasket weep, doesn't get hot, uses no water or oil and sounds as sweet as a sewing machine.

My question is when it fails, can I swap the 4.0 for a 4.6 without any major modification. Also, if I run a 4.6 on a 4.0 ecu, what - if any - damage would this do? I believe there was a 'switch' on GEMS equipped vehicles but not Thor.

OR

Alternatively, what sensible mods could I make to a good 4.0 lump to get stronger performance? Hi-Torque cam kit? re-map?

Any views appreciated as just shooting the breeze on this one.

No idea whether the ecu can be re-programmed (maybe via nanocom)?. I'd advise getting the HP24 transmission if upgrading to a 4.6 though. Also, the 4.6 is just as likely to fail as a 4.0l.
I had a Kent 180 cam in mine when i had a new top hat engine built (mine slipped the liners). Very impressed!

if you want it to fail it never will...

It's only when you dont want it to fail that it will !!!

I think you will need the 4.6 gearbox, if you obtain a 4.6 engine, as, I believe the box is a different lenght to the 4.0
A chap had a 4.6 litre car with a blown engine. I had a very low mileage 4 litre so he got that and his mechanis tried to fit it to his 4.6 gearbox - it didnt work as the measurements were different so he came back and had to have the 4litre gearbox off the original engine, all good.

Off the top of my head.....
Apart from the mechanical bits, you will need to swap over the engine harness, change the GEMS Ecu to the Motronic (Ideally the one matched to the engine) and get the Motronic EMS (Security code) read and noted. Next, the BECM will have to be unlocked and the settings changed from GEMS to Thor (Motrronic), the original EMS code changed to the one from the Motronic Ecu.
The reason for swapping the harness is that the Ecu connector shape and the pinouts on the GEMS to the Motronic plus the various sensor connectors and cable runs differ.