Photo of a 440 Six Pack V8 engine - Bruce Alan Bennett/ShutterstockWhen it comes to engines, muscle car fanatics have every reason to cherish the '60s and early '70s. The big three were on a roll: Chevy had 454 big blocks, Ford introduced the 427 "Cammer" and 428/429 Cobra Jets, while Chrysler's mighty V8 arsenal included the venerable 426 Hemi and a host of Mopar 440s. As you may know, the 427 Cammer and 426 Hemi were conceived as competition engines. And while Chrysler brought out a street Hemi with mods – including relaxed cam timing and a lower compression ratio — the street version would still be a high-rpm engine, much like its race-spec cousin.The Hemi was notorious for its upkeep, so the brains at Chrysler Corporation decided there was room for a more streetable engine with Hemi-like performance — one that would slot between the base 383 and the 426 Hemi in the Super Bee and Road Runner B-body lineup. Thus, in 1969, the 440 Six Pack was introduced. Called the 440+6 (or Six Barrel) in Plymouth land, this 440-cubic-inch Mopar V8 pumped out 390 horsepower and 490 pound-feet of torque thanks to the triple carb setup found atop its aluminum intake manifold.Although down on power versus the 425-hp Hemi, the torque figures remained identical to the 426. Because the design allowed max torque to arrive 800 rpm sooner than the Hemi, the Six Pack proved to be a more street-friendly alternative. Not only that, but the engine was significantly less expensive — optioning the Six Pack (as part of the A12 package) on a '69 Super Bee would've set you back $463, a relative bargain when compared to the $830 Hemi.AdvertisementAdvertisementRead more: 8 Underrated V8 Engines That Deserve More AttentionUnderstanding the top-spec Mopar 440Photo of a 440 Six Pack V8, showing the 440+6 branding - Barry Blackburn/ShutterstockUnlike the 426 Hemi, which featured hemispherical combustion chambers, the 440 Six Pack had its combustion chamber designed in a wedge-shaped fashion. While the Six Pack shared the same bore and stroke with other 440s within the RB (raised block) Mopar family, it had three Holley 2300 carburetors, unlike its four-barrel cousin — a single 350 cfm unit in the middle handling low-speed commutes, sandwiched between two 500 cfm Holleys that opened up when you buried the throttle. The upgrades did not end there, with the Six Pack also getting stronger connecting rods, moly-filled top rings, a unique counterweighted crank, chrome intake and exhaust valve stems, and Hemi-derived heavy-duty valve springs. Things changed in 1970, as Chrysler swapped the early Six Pack's Edelbrock aluminum manifold for a cast-iron unit. During that period, the Six Pack expanded across Chrysler's portfolio as a standalone option, offered on cars like the Barracuda, Charger, Challenger, Coronet, and GTX.Much like the 426 Hemi, the 440 Six Pack, among other great muscle car engines, had its days numbered as the decade progressed. Although both Chrysler engines were discontinued after 1971, three 1972 cars equipped with the 440 Six Pack managed to squeeze through – a Plymouth Road Runner GTX and Dodge Charger Rallye (both in Rallye Red) and another Charger Rallye in Top Banana Yellow, all built in August 1971. But how? Well, the Six Pack briefly remained part of the 1972 order guide before being pulled out, and apparently, only three buyers are known to have chosen the option.AdvertisementAdvertisementWant more like this? Join the Jalopnik newsletter to get the latest auto news sent straight to your inbox, and add us as a preferred search source on Google.Read the original article on Jalopnik.