Pontiac's  389 & 421

In 1955, Pontiac introduced its new Strato Streak V8, which displaced 267 cubic inches. This block is the basis for approximately 17 different engine displacements ranging up to 455 cubic inches. Hot rodders liked this feature because virtually all the engines were interchangeable without modifications. The engine grew to 370 cubic inches by 1958, and for 1959 Pontiac unleashed the legendary 389.

It was called the Tempest 420E engine in the Pontiac shrowroom brochure. (sample page below) Little  mention of the engine was made and certainly no pictures were presented, probably due to the AMA racing ban. God forbid we should see what the engine looked  like. What stupidity. At any rate, the 389 was available for 1959 with a top horsepower rating of 315 with tri power and 10.5 pistons. Over the years, the 389 would be available with a dizzying array of horsepower ratings, with up to 363 advertised for the 1961 389 Super Duty race engine. The factory tri power 389 was rated at 345 hp, so you can bet the SD was putting out a lot more than they were admitting to. Yeah, you could order one, dealer installed. These were good for 14.1 @ 100 in the quarter mile in a 1961 Ventura coupe.

For 1962, Pontiac officially introduced the 421 Super Duty, a killer Nascar engine sporting 2 four barrels, 11.0 pistons, and 405 horsepower at 5600 rpm. Ahem. Okay, we believe you. Hand built in a special factory tool room, the first Super Duty 421s debuted late in 1961 as race only engines. Pontiac was vague on their output, but estimates ranged from 373 to 405 bhp. These were the largest displacement engines  offered at the time, and they helped spark Detroit's cubic inch war.

NHRA rules changes for 1962 required engines and body parts for the stock classes to be production pieces. This forced the 421 onto the official equipment sheet as an expensive, limited run option. Fewer than 180 were built for 1962, its peak production year. Most went into Catalinas, though 16 or so were installed in Pontiac's new personal luxury coupe, the Grand Prix.

Street versions of the Super Duty had twin carburetors.

The '62 Super Duty 421 was officially rated at 405 bhp, but actual  output was closer to 460. Though street legal, these again were race ready engines with four bolt mains, forged rods and crank, solid lifters, and NASCAR heads. Stock car racing versions used a single four barrel, but street/strip Super Duty 421s had twin Carter 500 cfm four barrels and an aluminum intake manifold. They easily turned 13.9 @ 107 in street trim, getting from 0-60 in 5.4 seconds.

Free-flow cast-iron headers were fitted with easily removable exhaust dumps. Only three and four- peed manual transmissions were offered; Pontiac's automatic wasn't strong enough. Reinforcing the division's hard nosed performance attitude were a host of Super Duty options, including aluminum front end body clips and a weight cutting modified frame, saving about 110 pounds. To shave another 40 pounds, the factory would fit aluminum exhaust manifolds. They were intended only for quarter mile competition; Pontiac warned that subjected to more heat, the headers would melt. That would be cute, wouldn't it?

For 1963, Pontiac poured on so much performance that only an order from the highest power could slow it down. Unfortunately, that's what happened with the Super Duty Project. Super Duty 421s were back, tougher than ever. Compression jumped from 11.0:1 to 12.0:1, while other tweaks increased maximum shift points by 500 rpm to a screaming 6400 rpm. The four barrel version, set up for sustained high speeds, had 390 hp. The dual quad drag variant, now with aluminum exhaust manifolds standard and steel manifolds optional, was again underrated at 405 hp. A second dual quad drag rendition was introduced with a 13.0:1 squeeze. Pontiac timidly rated it at 410 hp. This is the one I had, in a 1957 Bel Air of all things. It was one of the most uncontrollable cars I ever owned.

1963 Pontiac Super Duty 421

Factory weight cutting again included aluminum front end pieces and included  by the famous Swiss Cheese frames, which had grapefruit sized holes drilled into the chassis rails. Super Duty 421s again came only with a Hurst shifted three or four speed manual transmission. Axle ratios up to 4.44:1 were offered. Dealers were advised to warn customers to maintain a minimum idle speed of 1000 rpm to insure adequate lubrication; that the engine would be cantankerous in cold weather, noisy all the time, and expensive to run; and that the large capacity oil pan reduced ground clearance. Gee, do you think they cared? Nobody's grandmother was going to order one of these, only psychos.

For those unwilling to take the Super Duty plunge, Pontiac introduced two new 421s that were more streetable. These High Output 421s had 10.75:1 compression and 353 hp with a four barrel or 370 hp with three two barrels. It was all too much for GM. In January 1963, the corporation withdrew from organized racing and killed the Super Duty engines. Just 88 '63 Super Duty V8s made it out the door, but Pontiac was poised to open a new performance frontier with the GTO.  Read more about the GTO here.

The 389 and 421 engines were continued through 1966. In 1967 Pontiac replaced the 389 with the 400. The 421  became the 428, with a top street rating of 376 horsepower. Quite a few of these still potent engines found their way into GTO engine bays. Cheater!!!! Who, me? Never. It's a 389. I swear. All in all, the 389-421 combination sold a lot of cars for Pontiac, and won a lot of races. They were always very competitive against MoPars, and are very collectable today.


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