Altitude Compensator

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Hitachi DCH-306 V-spec carburetors starting with 1976 B210 California models employ an Altitude Compensator mechanism. So the car runs in tune both at sea level and at high elevations -- and everywhere in between.

Overview

Same castings with and without the holes drilled:

1977

California (V) models use a carburetor with two fittings which lead to the air jets. A valve in the air cleaner connects to those via hoses. The valve is manually configurable to either H or L position.

Counties in USA 1,219m (4,000 ft) or more above sea high have been designated "High Altitude Counties" (see 1977 B210 Service Bulletin).

• At low altitudes: closed
• At high altitudes: open

Hitachi with 2-hose compensator.

1981

1981 use an Altitude Compensator with totally automatic operation. It works by a bellows moving per altitude, exposing more or less air to the air bleeds inside the carburetor.

Diagram from the 1981 B310 Factory Service Manual

Hitachi with vacuum secondary and 3-hose compensator.