Automotive Engines in Non-Automotive Applications Part 2

Buick Nailheads in the SR71 Starter Cart (AG330)

The Buick Nailhead 401 V8 found an unlikely second life as the starting system for the Lockheed SR-71 Blackbird. Because the SR-71's Pratt & Whitney J58 engines required extremely high rotational speed to initiate combustion, a conventional onboard starter was not going to work. Instead, the aircraft relied on an external start cart called the AG330, which used two Nailhead engines coupled together to spin a driveshaft that engaged the jet engine. This system could accelerate the J58 to several thousand RPM before fuel ignition.

Starting the SR-71 Blackbird's J58 Engines - AG330 Start Cart A view of the drive belt connecting the two engines

The Nailhead was selected largely due to its high torque output at low RPM, a defining trait of its undersquare design, large displacement and small valves. Additionally, Buick engines were readily available and robust, making them great for repeated high-load use in a ground-support role. Over time, these were replaced by big block Chevys, in most cases 454 cubic inch LS6 engines due to the aging Nailheads becoming less common, and parts being much more available for the generic big block Chevy engines. The Nailhead-powered carts became iconic among aviation enthusiasts.

We also have a soft spot for the Buick Nailheads at Speed Gems and have many kits to adapt them to different transmissions, mainly the GM automatic and manuals. Check out BU602 or BU1001 to hook your Nailhead to either a small block Chevy automatic, or manual transmission.

Pictures courtesy of thesr71blackbird.com

Chrysler 331 Hemi in Air Raid Sirens

The Chrysler 331 Fire Power Hemi V8 that powered air raid sirens in the 1950s was part of one of the most powerful civil defense warning systems ever built. These sirens were capable of producing sound levels around 138 decibels at 100 feet. For reference, a standard jet engine produces 150 dB at 80 feet while taking off and is enough to rupture eardrums. The engine drove a massive two stage air compressor system moving air at 2610 CFM at 7 PSI through a rotating chopper assembly, generating its unique wail. The air blast coming from the siren was enough to knock close flying birds out of the sky. Each engine was rated at 180 hp due to its lower compression of 7.2:1 and different camshaft grinds that allowed it to run at a moderate RPM for long periods of time. The siren could be heard as far as 10 miles away on the early version, and 16 miles in the later ones. Chrysler claims that 350 of these sirens were made in their production run, and cities that they serviced include Los Angeles, Chicago, New York and Miami along with many others.

At Speed Gems, we offer a few different kits to adapt to your Chrysler Hemi with extended bellhousing. Check out our WMO1101 to mate to a GM "Muncie" style transmission, WMO2301 to go to a small block Chevy automatic like a TH350, or WMO1301 to adapt to a Mopar 727.

Pictures courtesy of Hagerty and The Autopian

Chrysler Flathead 6's being combined to make the A57 Multibank Tank Engine

One of the most unconventional uses of automotive engines was the Chrysler Multibank A57, which powered certain variants of the M4 Sherman tank. Rather than designing a new engine from scratch, Chrysler engineers combined five 250 cubic inch inline-6 flathead engines into a single radial arrangement, all geared to a common output shaft. The result was a 30-cylinder engine producing between 370 and 425 horsepower.

This design was born out of wartime necessity. By leveraging existing tooling and manufacturing capacity, Chrysler was able to scale up production rapidly. While complex and heavy, it was surprisingly compact and the multibank engine proved effective enough to meet wartime demand.

While our kit will only work for a single Chrysler Flathead 6 engine not five radially, it gives you the ability to adapt to a GM small block Chevy transmission such as a TH350. For more information, check out WMO501 on our website.

Pictures courtesy of macsmotorcitygarage.com