[Paul Ceasrine]

Kip,

The 1967 Pontiac Firebird came with either the 400/325 HP or the 'optional' 400/335 HP 'Ram-Air'.

The 400/325 HP had the same,
* 10.75 - 1 Pistons
* Casting #670 Cylinder Heads (72.0 CC)
* 2.11" Intake / 1.77" Exhaust
* Cast Iron Intake Manifold

Note; To get a 'true {10.75 - 1 Compression-Ratio}, the Cylinder Heads would require a {65.0} CC Volume.

Differences;

400/325 HP - Camshaft
* .421" Intake / .424" Exhaust
* 273* / 289" Duration
* 47* Overlap

Valve Springs (Inner & Outer)
* 103 lbs. to 117 lbs. {Valve Closed}
* 239 lbs. to 257 lbs. {Valve Open}

400/325 HP- Rochester 750 CFM Quadra-Jet
* #7037263 (Manual)
* #7027272 (Automatic)
-------------------------------------------------------------------------------------------

400/335 HP 'Ram-Air' - Camshaft
* .424 Intake / .424 Exhaust
* 301* / 313* Duration
* 76* Overlap

Valve Springs (Inner & Outer)
* 135 lbs. to 145 lbs. {Valve Closed}
* 287 lbs. to 303 lbs. {Valve Open}

400/335 HP 'Ram-Air' Rochester 750 CFM Quadra-Jet
* #7037273 {Manual}
* #7037276 {Automatic}