Thread: Replacing serpentine-belted 3.9 with earlier motor

The crankshaft is the main problem if you want to use the crank driven oil pump, as the keyway in the front of the crank is not long enough to engage the oil pump gear.
AFAIK BLock and heads are the same but you would have to dismantle the whole motor to have the crank keyway extended.
All Rover blocks are BACKWARD compatable but unfortunately they were not clairvoyant so they are not FORWARD compatable.
Regards Philip A

Hello POD,

You can if you wish use the engine from the 1990 RR as it is. Only if you wish to use change the timing covers, water pumps etc and use the crankshaft driven oil pump will you need to follow what PhilipA advised regarding the crankshaft keyway.

The engine block and heads are essentially the same as far as external dimensions are concerned. The Rover heads over the years did see different numbers of bolt holes on the ends for accepting brackets etc, and the size of at least one of the required bolt/s did change.

Ron.

I am assuming he will not have the V belt alternator,power steering pump,aircon compressor , water pump etc with the 90 block .

If he has all of them then he can just fit the 90 as is.

Regards Philip A

if the engine is complete and was attached to the same gearbox it will just drop in and bolt up but you will have to faf around with the management, hoses, fan and some other minor things.

Watch for the imperial-metric change over it will pay to double check all the mounting bolts for the thread type and that you have the same type.

IF its not complete (alternator, power steering, aircon) its a bit more of a headache but it is achievable.

Thanks for the good info. Its a huge advantage to have a heads-up on this stuff before starting a job.
I do have all the ancillaries on the earlier motor, but I'm hoping to be able to keep the Disco set up with the serpentine belt. What if I were to swap the crankshafts, i.e. keep the disco crankshaft in the disco, but in the different block? Might cost me a machine and a set of bearings, but would it work?