Quote:
Originally Posted by Sternjaeger II
Sleeve valves? No thank you 
The Sabre was a bit of a trouble child, and considering the sheer weight and size of the thing, you could probably compare it to a radial more than an inline. |
Salute
By 1944, the Sabre had overcome its teething problems, and was a reliable performer while producing 2600 hp from 36.5 liters, and that was without a fairly primitive supercharger. With an updated supercharger, it produced unheard of amounts of horsepower in later models, 3500 in the initial Sabre VII, out just after the war, and up to 5500 hp in the final generation Sabre VII engine which did not go into production.
It got its performance from higher rpms allowed by smaller piston and shorter stroke, sleeve valves, (which breathe better) and better volumetric efficiency from the H block design.
If piston engines driving props had remained the cutting edge of aircraft propulsion, then the H block engine would have been in the forefront, but because Jet turbines were obviously superior, the Sabre was discarded, and the simpler but more reliable Radials were kept in production as propulsion for 2nd line aircraft.