The original FirePower Hemi has a bore of 3.815 inches and the stroke is 3.625 inches offering 331 cu in displacement from 1951 until 1955. The engine produces 180 bhp with the two barrel carter carburetor although for the ’55 model year the Chrysler C-300 is equipped with dual Carter WCFB four barrel carburetors.
© Hofmeester | Dreamstime.com – A Red Desoto Vintage Car Of 1955 Photo
The 331 is the only Hemi until the 1956 model year with the release of the 354 cu in engine with a 3.9375 inch bore and a stroke of 3.625 inches and delivers 340 bhp (254 kW) in the Chrysler 300B but the model has an option of a higher powered version offering 355 hp (265 kW) which is the first engine produced in North America to deliver one horse power per cubic inch of displacement. The New Yorker and Imperial are equipped with the 354 engine producing 280 bhp (209 kW). Prior to 1972 horsepower is an SAE gross figure but from 1972 onward the figure is a net one. Particularly heavy duty trucks use a version of the 354 V8 as the “PowerGiant” engine and it could be had with a one, two, or four barrel carburetor set ups from 1957 until the 1959 model year on the heaviest duty Chrysler pick-ups. For 1956 the New Yorker, Chrysler 300B, Custom, and Crown are equipped with the 354. In 1957 Dodge D-301 and the “C” series pickups also use this engine. Certain models are equipped with the 354 having hybrid polyspheric heads rather than the Hemi design. They bear some features of both the Hemi and the traditional wedge head but are lighter than the Hemi heads and are in some of the 354 engines marketed in 1957. The 1957 model year sees the release of the 392 raised deck Hemi engine with a 4.00 inch bore (101.6 mm) and a 3.906 inch stroke with this engine the deck height is 10.87inches a full .5 inches (13 mm) taller than previous blocks. The new heads are wider but will still accommodate earlier design manifolds. Chrysler for 1958 offers two versions of the 392 equipped with a single four barrel carburetor. A lower compression of 9.25:1 will deliver 325 bhp (242 kW) while if you choose the one with 10:1 compression it will deliver 345 bhp (257 kW). For ’57-’58 model years the Chrysler 300C and the 300D you could have optionally chosen the dual four barrel set-up which will give 375 bhp (280 kW). For 1958 there is a little known and very rare Bendix “Electojector” fuel injection system available for the 392 which delivers 390 bhp (291 kW) but due to problems with reliability of the under-developed computer control for the injectors 15 of the 16 300D units were retrofitted with carburetors. Drag racers found the 392 Hemi engines to be extremely dependable as well as powerful and many were used competitively into the 1970’s.
© Mtoome | Dreamstime.com – 1958 Chrysler Imperial Photo
Desoto is also using its own engineers to develop the Hemi with a new 290.8 cu in (4.8 L) engine sporting a 3.72 inch bore in 1955. For 1956 the same engine now has a 329.9 cu in (5.4 L) displacement and although the bore is the same at 3.72 inches the stroke has been increased to 3.80 inches (96.5 mm) and the heads are sitting on a raised block to accommodate the longer stroke. The Adventurer is the premier Desoto model in 1956 and the 329.9 Hemi develops 343 hp (256 kW) using a special hydraulic camshaft slightly higher 9.51:1, and a dual Carter WCFB four barrel carburetor set up followed by the lesser Firedome and Fireflight models offering the same carburation in 1957. However the Adventurer kicks it up a notch in 1957 with a 344.6 cu in (5.6 L) Hemi with the same compression as last year, a slightly longer stroke of 3.80, now equal to the 3.80 inch bore, and the same carburetor set up as last year it now develops 345 bhp (257 kW)