The message
from Andy Champ contains these words:

its rare to see more than 70bhp/liter from any normally aspirated road
engine.

Almost any bike.

Or if you want cars - Toyota 3SGE (in the MR2 Mk2 among others), 2
litres, 158BHP from the later UK models, and over 200 if you can get
hold of one of the Japan-only BEAMS engines. Though the last does have
variable valves etc...

Or the BMW 320, 150BHP/ 2 litres from 1991.

75bhp/litre. 11 years on and it had hardly changed - 170 from 2.2 or 77/litre.

Or IIRC the Cavalier GSI, 156 BHP, 2 litres, and that's back a few years.

If you say normally aspirated, *carburettor* engine, then I'll let you
have it.

Well the Elan Sprint had much the same output as the 2002 320 BMW and
that fits the carburettor bill. OTOH it is and was a rare car.

--
Roger Chapman