What are the specs on a Pontiac 455?

Answer 1

Horsepower and torque specs varied greatly depending on the year of production, highest per year were:

1970 455 =360-370hp@4600, 500lbft@2900 (hp depending on chassis engine was installed in, GTO got the lower hp rating) (only year of high compression 455, standard D port cylinder heads)

1971 455ho=335hp@4800rpm, 480lbft@3200(Round port heads, first year of low compression, massive torque, great street engine)

1972 455ho=300hp@4000rpm 415lbft@3200 (Round port heads, new sae net rating system, slight cylinder head change, nearly same engine as 1971)

1973-1974 455sd=290hp@4000rpm, 390lbft@3600rpm (Round port heads, under rated the strongest 455 Pontiac ever produced)

1975-1976 455=200hp@3500rpm (smog motor low performance)

There were several other lower performance 455 Pontiacs produced during the engines 1970-1976 run. Those listed above are the highest performance available each year.

Engine parameters for all 455 Pontiacs:

bore-4.15

stroke-4.21

Main bearing size-3.25

rod bearing size-2.25

connecting rod legnth-6.625