Easy answer... Ford's Model T Engine.
Inline 2.9lt, 4-cyl.
Cost a few bucks back in the day for 20odd horses & is now worth thousands for you...
hahahahaha
Seriously - perhaps the YB series Cosworth 2lt engines that they put in Ford RS - capable of about 550 horses
You may enjoy this -
872 bhp Ford Cosworth YB Dyno run! - YouTube