Page "Pontiac GTO" Paragraph 56

A new option was Pontiac's 455 HO engine ( different from the round-port offerings of the 1971-72 cars ), available now that GM had rescinded its earlier ban on intermediates with engines larger than 400.

The 455, a long-stroke engine also available in the full-size Pontiac line as well as the Grand Prix, was dubiously rated by Pontiac as only moderately stronger than the base 350 HP 400 cu.

in.

and less powerful than the Ram Air III.

Curiously, per the Pontiac brochure of the time, the same spec 455 installed in the Grand Prix model was rated at.

The camshafts used in the Ram Air III and the GTO 455 HO were the same.

For example the manual transmission 455 HO's used the same 288 / 302 duration cam as the Ram air III.

The 455 was rated at at 4, 300 rpm.

Its advantage was torque: at 2, 700 rpm.

A functional Ram Air scoop was available.

Car and Driver tested a heavily optioned 455, with a four-speed transmission and 3. 31 axle and recorded a quarter mile time of 15. 0 seconds with a trap speed of.

Car Lifes Turbo-Hydramatic 455, with a 3. 35 rear differential, clocked 14. 76 seconds at, with identical 6. 6 second 0-60 mph acceleration.

Both were about slower than a Ram Air III 400 four-speed, although considerably less temperamental: the Ram Air engine idled roughly and was difficult to drive at low speeds.

The smaller displacement engine recorded less than of gasoline, compared to-for the 455.