VGEN V GARAGEGM GEN V LT · TECHNICAL REFERENCEBuild DatabaseAbout
Gen V LT valvetrain and cylinder-head assembly

VALVETRAIN · SERVICE GUIDE

Cam Base-Circle Procedure

Use the EO / IC method to position each lifter on the camshaft base circle before tightening the rocker arm.

Torque a rocker only when its lifter is on the cam lobe’s base circle.

The EO/IC method uses the opposite valve event on the same cylinder to put the rocker being tightened safely on the base circle. Rotate the engine by hand in its normal direction and watch the rocker motion closely.

Rocker / valve identification

This map is oriented exactly as you see the engine while standing at the center of the front bumper and looking toward the firewall.

REAR / FIREWALL
PASSENGER SIDE · BANK 28E8I6E6I4E4I2E2I
DRIVER SIDE · BANK 17I7E5I5E3I3E1I1E
FRONT / RADIATORYOU
I Intake rocker / valve · E Exhaust rocker / valve
READING ROCKER MOTION

Watch the valve-tip end of the rocker. Rocker tip moving DOWN = valve opening. Rocker tip moving UP = valve closing. The pushrod end moves the opposite direction, so use the valve-tip end as your visual reference.

1 · Intake rocker — EO

EO means Exhaust Opening. Watch the exhaust rocker on that cylinder while rotating the engine.

  1. Rotate the engine by hand in the normal direction.
  2. Watch the valve-tip end of the exhaust rocker.
  3. When the exhaust rocker tip just begins moving down, the exhaust valve is beginning to open.
  4. Stop. The intake lifter is on the base circle.
  5. Verify the intake pushrod is seated correctly in the lifter and rocker.
  6. Torque the intake rocker bolt to 22 lb-ft.
EO → TORQUE INTAKE

Exhaust rocker tip starts down → exhaust valve starts opening → torque the intake rocker.

2 · Exhaust rocker — IC

IC means Intake Closing. Continue rotating the engine and watch the intake rocker on that cylinder.

  1. Watch the intake rocker tip move down as the intake valve opens.
  2. Continue rotating through full intake-valve opening.
  3. Keep rotating until the intake rocker tip has moved back up and the intake valve is nearly closed.
  4. Stop. The exhaust lifter is on the base circle.
  5. Verify the exhaust pushrod is seated correctly in the lifter and rocker.
  6. Torque the exhaust rocker bolt to 22 lb-ft.
IC → TORQUE EXHAUST

Intake rocker tip comes back up → intake valve is closing → torque the exhaust rocker.

3 · Repeat cylinder by cylinder

Repeat EO for each intake rocker and IC for each exhaust rocker. This removes the guesswork of relying on a fixed crank-position or cylinder-group shortcut when the cam profile or engine position is uncertain.

DO NOT TORQUE AGAINST VALVE-SPRING LOAD

If the rocker being tightened is visibly opening its valve, stop and reposition the engine. The lifter is not on the base circle.

4 · Final check

After all 16 rockers are torqued, rotate the engine through two complete crankshaft revolutions by hand. Watch for normal valve motion and verify that every pushrod remains correctly seated.

Torque baseline: 22 lb-ft for the L83/L86 rocker-arm bolt application. Verify application-specific hardware and service information when using this procedure on other Gen V LT combinations.