Match Race 1972 ~ 'Duster 340 vs 'GTO 400'

O-M-R

On the 1972 Pontiac GTO

Available Engines
* 400/250 HP {L-78}............ 8.2 to 1
* 455/250 HP {L-75}............ 8.2 to 1
* 455/300 HP {L-55} 'HO'..... 8.4 to 1

The 400/250 HP {L-78} outran the 455/250 HP {L-75}.

The 455/250 HP {L-75} was available in an 'Automatic Only'. Back-in-the-day, this
was the Engine that the Pontiac GTO 'Gear-Heads' said to stay away from.

Big Cubes, but no Horsepower. Low-End Torque was massive though {475 Ft/Lbs. @ 3400 RPM}

The #7M5 Cylinder Heads were/are regarded as one of the poorest designed 455 Heads. Big monster
Combustion Chambers from the factory {114 CC's}, and the Exhaust Ports were poor flowing
despite the 1.77" Exhaust Valve.

If you wanted to use them, Pontiac recommended milling them {.055"} down to 101.8 CC's. to get
the Compression up to {9.22} from an anemic {8.20}.

Then work like a Mad-Man on grinding out the Exhaust Ports, and smoothing out the Intake Ports and Valve Bowls.

That's why only a few of the 455/250 HP 'L-75' GTO's exist today.........only 240 Built by Pontiac.