Transforming a standard Lamborghini 4.0L to a larger size was a real challenge. In order to increase
the stroke from 62mm to 80mm required
that the deck of the block be raised by
9mm by the use of custom deck plates.
After the block was raised, then many
other factors are changed as well (cam
chain, head studs, tensioner sprocket, liner
length, etc.). Additionally, the cam profiles
had to be re-designed for low rpm (1,500
to 5,500 rpm range).
When the engine was dyno tested,
the Weber carbs needed to be completely
re-calibrated for the larger displacement
and lower rpm running range.
All of the modifications were successful
and the engine made good low rpm torque
which is essential for a marine application.
This engine and the sister counter-
rotating engine will be installed in a Riva
Aquarama speedboat once owned by Mr.
Lamborghini.
