07/09/2026
The factory said 290 HP. The factory was lying by 66 horsepower. Dodge Garage's own dyno testing, published half a century later, put the 340 Six Pack at 356 HP with factory exhaust manifolds and 376 HP with headers. Three hundred fifty-six horsepower from 340 cubic inches. That is 1.05 HP per cubic inch from a carbureted, naturally aspirated, pushrod small block with cast iron heads and three two-barrel carburetors. The same benchmark the L84 Fuelie hit with mechanical fuel injection. The 340 Six Barrel did it with three Holleys and a lie on the spec sheet.
The lie was deliberate and strategic. Chrysler had already rated the base four-barrel 340 at 275 HP when it actually made approximately 320 HP on a modern dyno. When the Six Barrel upgrade added three Holley 2300 two-barrel carburetors on an Edelbrock aluminum intake manifold, the output jumped to 356. Chrysler rated it at 290. Fifteen horsepower more than the base 340 on paper. Sixty-six horsepower more on the dyno. The gap between the advertised number and the real number was 23 percent. Chrysler played the same underrating game every manufacturer on this page played, but with the 340 Six Barrel they played it harder than anyone except the 426 Hemi. Insurance companies priced premiums based on published horsepower per pound. A 290 HP rating kept the premiums manageable. A 356 HP rating would have priced 22-year-old buyers out of the car Chrysler built specifically for them.
The 340 Six Barrel existed for one purpose: SCCA Trans-Am homologation. The series limited displacement to 305 cubic inches, but required manufacturers to produce street-legal versions for sale to the public. Chrysler needed a competitive small block for the AAR 'Cuda (named for Dan Gurney's All American Racers team) and the Dodge Challenger T/A. The 340 TA engine was not a standard 340 with carburetors bolted on. The block was stress-relieved with high nickel content and filled oil pan rails. Additional material was cast at the main bearing web area to accept four-bolt main caps, although the production version used two-bolt caps. The cylinder heads were J castings with modified pushrod holes drilled offset from the ports so the ports could be enlarged during race preparation without breaking through into the pushrod passages. Adjustable rocker arms similar to the 426 Hemi. Rocker shafts with banana-shaped l**e spreader grooves. A fiberglass fresh air hood sealed to an oval air cleaner that fed cold outside air directly to the three carburetors. Side-exit exhaust that dumped in front of the rear wheels. This was a race engine wearing a street registration.
The center Holley handled normal driving. Cruise at 2,000 RPM on the highway, only the center two-barrel was open. Tip into the throttle past a vacuum-actuated threshold and the two outboard carburetors opened simultaneously. Six barrels of carburetion feeding six hundred CFM of combined airflow into 340 cubic inches. The transition from two barrels to six was not gradual. It was a switch. The engine went from cruising to screaming in the time it took the vacuum diaphragms to open the outboard throttle plates. Drivers described it as a second engine turning on. The intake roar when all six barrels opened was unlike anything a single four-barrel produced. Three separate carburetors inhaling through three separate throats created a harmonic that no single carburetor could replicate.
Plymouth built 2,724 AAR 'Cudas. Dodge built 2,399 Challenger T/As. One model year. 1970 only. Approximately 5,100 cars total with the 340 Six Barrel. The rarest Mopar small block in a production car. Named after Dan Gurney on the Plymouth side and Trans-Am on the Dodge side. Every one with a 340 that the factory said made 290 HP and the dyno said made 356. The most underrated, most dishonestly advertised, and most exciting small block Chrysler ever built. Six barrels. 340 cubic inches. 356 real horsepower. And a spec sheet that said 290 because the truth would have cost more in insurance than the car cost to buy.
