its worth what ever you are prepared , or indeed anyone else is prepared to
pay for it. a Cooper 998 is little different from any 998 engine. The cost
of rebuilding one to use ina car is probably more than its really worth.
They are not that much more powerful than a stock engine and I think you
would be very dissapointed. Its true value is to someone who collects Cooper
998 and would want it just for the spare potential. Or if they happen to
have the original car it came out of and the two can be re-united to make a
whole again. The only significant difference is the cam ,head and pistons.
Otherwise its stock standard. there are much better grinds of cam and
aftermarket heads are 10 a penny to suit a 998/1000 cc engine. The gearbox
will need to be rebuilt more than likely ...so save your self the money and
hassle and just get a good 1275, which will even in standard form have more
power, better tourque etc.
Its value is in its curiosity, not its power potential which is not greater
than a standard engine of similar capacity...key word is potential

Tim
Owner of a Cooper 998.....for 27 years, as well as 1275 S, 1071 S, and a MPI
Cooper S works