We're trying to set up a bit of a hybrid rover engine, its a 4.6block and heads with 3.9 inlet manifold and timing cover and the 4.6 plenum chamber.

It has a Lucas 35DLM8 dizzy on it which has two vacuum connections, presumably one advance and one retard.

Where do these need piping up to?

Without them connected at all it runs fine, but with the advance side piped to the plenum on the engine side of the throttle, it pulls too much advance on idle, so I'm gussing it needs both sides connecting, and probably to the right places!

any ideas?

yes - once is advance, the other for retard.

unfortunately without thinking or looking in the Haynes, I cannot tell you how to connect the retard. (advance usually goes to inlet manifold)

Is it the correct dizzy? My 3.9's dizzy only has one vac pipe, which is connected to the plenum.

Is it the correct dizzy? My 3.9's dizzy only has one vac pipe, which is connected to the plenum

+1

My dizzy had one vac pipe connected to the plenum and one blocked off with a bolt.

cheers folks, spare connection now blanked.