The COBRA (Tin Block) engine is undoubtedly the most unique concept used in any or the Crosley cars and trucks.
It was during the summer of 1943 that Powel Crosley Jr first heard or an all steel stamped, copper hydrogen brazed engine. Paul Klotsch, chief engineer of Crosley Motors Inc, soon was visiting Lloyd M. Taylor of Taylor Engines Inc, California, the inventor of the engine. The horsepower, fuel consumption and other performance data was so outstanding Crosley took an exclusive license under all patents.
Before the end of the war the Navy became interested in the lightweight high output of the engine and six engine generator sets were built, which ran at 5000 RPM developing 35HP. Crosley and the Navy performed exhaustive tests including running one engine continuously for 1200 hours.
The Crosley engine easily won the contract, meeting or exceeding all specifications. The Armed Services used the tin block engine for air drop able self contained generators, generators for PT Boats, amphibs and many other places, that lightweight power plants were needed.
Some civilian uses, other than the Crosley Automobile from 1946 to early 1949, were truck refrigeration, boats and the Mooney Mite airplane.
The COpper BRAzed engine had a bore of 2.5 by 2.25 stroke to keep piston speed down at high RPM, this gave a displacement of 44 cu in. Military version ran compression ratios as high as 9 to 1 on 100 octane fuel for maximum of 36HP at 5600 RPM (.8HP per cubic inch displacement). The 1946 car engine had a lower compression ratio of 7.5 to 1 and horsepower was reduced to 26.5 at 5200 RPM.
A vertical shaft with bevel gears was used to drive the overhead camshaft instead of a more conventional chain drive so that the lubricating oil could be fed up through it to pressure feed the cam bearings.
The crankcase was made out of cast aluminum alloy and held the
crankshaft in 5 main bearings giving a very strong lower unit for the
COBRA. The 4 cylinder block was constructed out of about 125 steel
stamping. The pieces were held together by press fit, spot welds or
crimping before brazing. The block is then copper brazed in a specially
constructed 60 foot long furnace at 2060 degree F in a neutral
atmosphere. The hardness of the alloy steel was controlled by the speed
of cooling. The finished block weighs an extremely light 14 pounds.
Inside, the water jacket was first plastic coated, later blocks had a
zinc coating on the inner liners.
Comparing the pre-war 2 cylinder engine and the copper brazed engine shows the weight was reduced from 188 to 133 pounds and horse power was increased from 12.5 to 26.5.
Crosley showed the durability of his new engine by filling a block with water and freezing it solid without cracking the block.
Dependability was poor on the early engines that Crosley put in his cars. The engines were essentially the military version with slightly improved valve trains. Used on the road at variable speeds put different demands on the engine than the constant speed that they were used at in generator sets.
By 1947 the COBRA was reasonably dependable. If serviced properly the engine was good for 60,000 miles or so. Low water was probably the COBRA's worst enemy, causing burnout, warping and water leaks. The other problem plaguing the engine was rust out in the water jacket caused by electrolytic action when the plastic or zinc inner liner broke down, this was further aggravated by salt based antifreezes that were in wide use at the time.
Early in 1949 Crosley changed to the cast iron block CIBA (cast iron block assembly) having the same horsepower and displacement at an increase of about 30 pounds in weight.
"New Engine" Consumer Reports, (Jan. 21, 1946)
"Brazed Stampings Reduce Engine Weight" Machine Design (Feb. 1946)
"Crosley The Mighty Mite" Old Car (July 1972)