The first 'new' Countach was the LP500S; Ferrari had unveiled their Boxer, which was faster than the Countach LP400S, so Lamborghini had to do something.
They tried a turbo-charged version of the 4.0-Liter engine, but because of cooling problems, this project as abandoned in an early stage. Another option was tried out, but in the end, the best thing to do was to increase the displacement up to 4754 cc by enlarging both the bore and stroke.
Other changes were also made to this new engine, like redesigning the combustion chambers, lowering the compression ratio, fitting revised cams and larger Weber side drought carburettors.
The exterior of the Countach didn't change much, A minor change was made to the side-mounted front turning indicators, and naturally the inscription on the tail panel changed, on some later examples this said '5000' instead of '500', a less well visible change was the use of OZ aluminum-alloy wheels instead of the Magnesium Campagnolo used on the early LP400 S models. These OZ rims were slightly heavier but retained the same design as on the later LP400 S edition.
The interior didn't change much either, the lining used for the inner door became more luxurious with some added stitching, on the LP400S this panel was a single piece of leather with no stitching whatsoever, also the lock on the glove box was altered to remedy a problem with the earlier types.
The enlarged 5-Liter engine needed just as much fresh air as the 4-Liter unit, so the intakes behind the doors remained the same. On the March 1982 Geneva Auto Show, the new LP500 S was introduced, the old LP400 S remained available, but naturally did not sell very well anymore. The LP500S was a little heavier, about 290 Kg., but was still a lot faster than the LP400 S. This 'all-new' Countach outsold its predecessors in only two years, in its three-year production run, the LP500S sold 323 units.
The LamboCARS.com extensive specifications chart on Countach LP500 S ...