higher compression, and was good for for 1963–1964, and for 1965 - 1966 and the final year, 1967. 350 HO In 1968, there was also a 350 "HO" which had increased power with the addition of higher compression #18 heads (#17 and #46 were the most common 2-barrel heads), a four-barrel carburettor and matching intake that was also used on the 400 and 428 engines. There was also the addition of dual exhaust, and for vehicles equipped with a manual transmission, a slightly more aggressive camshaft. In 1969 the 350 HO was upgraded again with the addition of the 400 HO cam, commonly referred to by enthusiasts as the 068 cam. Also added was the #48 casting number heads with a chamber for higher compression, along with larger valves. Free-flowing exhaust manifolds from the 400 Ram Air were used late in the model year. This was underrated at . 400 HO Officially named the Quadra-Power 400 for 1967 and renamed 400 HO for 1968, the 400 HO was first offered for 1967 as the third engine in the GTO line after the automatic-only 400 2-barrel and the standard 400 4-barrel (the 400 HO would not be offered in the Firebird until the 1968 model year). For the 1967 GTO the engine was rated at and had the cast-iron headers. The camshaft was the HO cam with 288/301 duration. It was the top-of-the-line engine unless one opted for the "Ram Air" V-8 derived from it. As Pontiac's 1967 performance brochure said, "You can add the Ram Air induction hood scoop and new high output cam and valve springs to the Quadra-Power 400 for better top end breathing." But the "Ram Air" 400 also mandated steep 4.33:1 gears(or 3.90:1 in Firebird), making the Quadra-Power 400 (400 HO) the top practical street engine option for most drivers. Standard ratio with the 400 was 3.55:1(except 3.36:1 in Firebird for 1969) regardless of transmission(3.23:1 for cars with air conditioning). The 400 HO was offered as an option for 1967-1970 for GTO and 1968-1970 for Firebird. For 1969-1970 GTO the 400 HO included driver operable Ram Air induction and was renamed "400 Ram Air" for 1969 and just "Ram Air" for 1970. In the Firebird Ram Air induction for the 400 HO was a separate option for 1969(included with Trans Am) and included with the engine(optional in Formula; included with Trans Am) in 1970. 400 W72