What you see pictured above is a Chrysler Air Raid Siren, the most powerful siren in the world. It's the size of a car, measuring near 12-feet in length and standing more than 6-feet tall. It also weighs twice as much as today's typical car. This gigantic siren is powered by an 180-HP Chrysler Industrial V-8 HEMIĀ® gasoline engine. The super-duty engine directly drives a three-stage compressor that blows 2,610 cubic feet of air a minute, at nearly 7 PSI, into a giant siren rotor. The compressed air screams through the chopper and out through six giant horns with an exit velocity of 400 miles per hour. The result is an incredibly loud 138 dB sound (measured 100 feet from the siren). The loudness of this siren is unmatched by any other warning device ever sold, ever. It's also considerably louder than the largest steam whistle or horn. As if that were not dramatic enough, the whole unit, engine and all, slowly rotates one and one-half times a minute on its iron turntable base.

A few hundred of these monstrous Cold War sirens were produced and sold during the 1950's. Many remained in service for twenty plus years, sounding only for routine tests. Most people who lived in major metropolitan areas during the 1950's and 60's will remember the siren tests. Those particularly, who lived in or near Los Angeles, Seattle, Kansas City, Chicago, Detroit, Cincinnati, Pittsburgh, New York and even Miami could hear the haunting siren wail of a Chrysler Air Raid Siren.

These were air raid sirens. In the 1940's they warned communities of enemy aircraft. In the 1950's and 60's they stood ready to warn of incoming enemy missiles. It's unlikely that were ever used for any other purpose. The air raid sirens Chrysler built were invented by Bell Telephone Laboratories during World War II. Three different production models of this siren design were made by Chrysler between 1942 and 1957. The Cold War model was the loudest and was built only in the six years ending in 1957.

The Chrysler Air Raid Siren is so powerful that it can reportedly start fires with just the sound vibrations it produces. It can turn fog into rain, clearing the sky. It can produce an effective 70 dB air raid signal for a distance of two miles, and under proper conditions can be heard 30 to 50 miles away. Its advertised effective range was four miles in every direction. That's a long way!

Because of the extreme sound power emitted by these sirens and the desire that their coverage area be extended as far as possible, they were usually mounted high on a steel tower or on top of multi-story building. As a result these sirens were always heard, but rarely seen. For most of the visitors to this website, this will be the first opportunity they have ever had to see the siren that prompted "Duck and Cover" drills.

The engine used in the Cold War model Chrysler Air Raid Siren is the same Hemi FirePower Engine Chrysler introduced in 1951 as their first V-8 engine. It represented an impressive improvement in engine design that produced 180 horsepower and a then high compression ratio. When Chrysler Air Raid Sirens were being retired during the 1970's they became a popular source of hot rod engines. According to a leading supplier of aftermarket parts for early Hemis, the engine can easily attain 330 horsepower and considerably higher than factory torque. Boring and blowing this engine can produce respectable performance statistics for any hot rod enthusiast.

Originally posted by Chuck 98 RT/10
The 426 you're thinking of is from the 60s. This air raid motor is from the 40s and 50s.