Deceleration Valve: Adjustments

BCDD ADJUSTMENT

1. Connect rubber hose between vacuum gauge and intake manifold, then run engine until it reaches normal operating temperature and set idle to specification.
2. Run engine under no load. Increase engine speed to 3000-3500 RPM, then quickly close throttle valve.
3. Manifold vacuum pressure should rise to 23.62 inches Hg or above, then gradually decrease to a certain level and remain at this level temporarily. This is the operating pressure. In most cases it will drop to operating pressure.
4. Check that BCDD operating pressure is within 21.65-23.23 inches Hg at sea level.
5. If it is not within specified range, turn adjusting screw until correct adjustment is made.
6. Race engine and check for adjustment. If it is lower than sea level, turn adjusting screw until correct adjustment has been made.
7. Race engine and check for adjustment.
8. If engine speed cannot be decreased to idle, turn adjusting screw counterclockwise so that operating pressure is on high vacuum side, .79 inch Hg from specified value.
9. Turn adjusting screw 1/4 turn clockwise so that operating pressure drops .79 inch Hg.
10. If operating pressure still cannot be clearly determined, turn adjusting screw counterclockwise so that operating pressure is on high vacuum side, 1.97 inches Hg from specified value.
11. Turn adjusting screw 1/2 turn clockwise. Operating pressure should be correctly set even if engine speed cannot be reduced to idle.