“The 3.9 certainly continued to appear in the brochures. Often described as 4.0 litre”
The 4.0 litre engine is also called the GEMs engine.
The 3.9 and 4.0 have the same bore and stroke, the 4.0 block has cross bolted mains.
The 3.9 front case has a distributor and oil pump driven from the camshaft.
The 4.0 does not have a distributor, the oil pump is crank driven, consequently the crank has a greater overall length, the ancillaries are driven from a serpentine belt, thus these parts aren’t individually interchangeable.
Naturally enough, interim engines exist with both distributors and crank driven oil pumps!
The Des Hammill book “How to power tune Rover V8 engines” is an excellent source of information and will talk you through the variations, [whereas the 2x David Hardcastle books are better suited to mopping up spilt oil].
As noted above the MMC 4.6s were in effect big bore 3.9s with 3.9 distributors, heads and injection system. At the time the factory was using a 3.9 & 4.6 engine to produce one 4.6; zero miled 3.9 short blocks were available as spare parts from MMC and jolly good value they were.
Last edited by Horror; 08/02/18 09:45 PM. Reason: Fat fingers
