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KMP1171
KMP1171, ASE Certified Technician
Category: Chevy
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Experience:  Mech for 20yrs and GM Specific for 15
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at tdc #1 what valves should be open and where should the rotor

Customer Question

at tdc #1 what valves should be open and where should the rotor be pointing, how to adjust please .
Submitted: 4 years ago.
Category: Chevy
Expert:  KMP1171 replied 4 years ago.
VIN Z
Valve arrangement-4.3L <a href=engines (E=Exhaust; I=Intake)"/>

Valve arrangement-4.3L engines (E=Exhaust; I=Intake)

Click to Enlarge
Adjust the rockers, by rotating the pushrods between your thumb and forefinger to feel for play

Adjust the rockers, by rotating the pushrods between your thumb and forefinger to feel for play

Click to Enlarge

This engine utilizes hydraulic valve lifters which means that a valve adjustment is NOT a regular maintenance item. The valves must only be adjusted if the rockers arms have been disturbed for any reason such as cylinder head, camshaft, pushrod or lifter removal.

For 1993-94, the 4.3L (VIN Z) engine may be equipped with either of 2 rocker arm retaining systems. If your engine utilizes screw-in type rocker arm studs with positive stop shoulders, no valve lash adjustment is necessary or possible. If equipped, please refer to the 4.3L (VIN W) valve lash information, found later in this section. If however, your engine utilizes the pressed-in rocker arm studs, use the following procedure to tighten the rocker arm nuts and properly center the pushrod on the hydraulic lifter:

  1. Disconnect the negative battery cable for safety.

  2. Remove the engine cover from the passenger compartment for access.

  3. Remove the rocker arm covers. For details, please refer to Section 3 of this manual.

  4. To prepare the engine for valve adjustment, rotate the crankshaft until the mark on the damper pulley aligns with the 0° mark on the timing plate and the No. 1 cylinder is on the compression stroke. You will know when the No. 1 piston is on it's compression stroke because both the intake and exhaust valves will remain closed as the crankshaft damper mark approaches the timing scale.

Another method to tell when the piston is coming up on the compression stroke is by removing the spark plug and placing your thumb over the hole, you will feel the air being forced out of the spark plug hole. Stop turning the crankshaft when the TDC timing mark on the crankshaft pulley is directly aligned with the timing mark pointer or the zero mark on the scale.

  1. With the engine on the compression stroke, adjust the exhaust valves of cylinders No. 1, 5 and 6 and the intake valves of cylinders No. 1, 2 and 3 by performing the following procedures:

    1. Back out the adjusting nut until lash can be felt at the pushrod.

    2. While rotating the pushrod, turn the adjusting nut inward until all of the lash is removed.

    3. When the play has disappeared, turn the adjusting nut inward 1 additional turn for 1988-93 engines or 13/4 additional turns for 1994 engines.

  2. Rotate the crankshaft 1 complete revolution and align the mark on the damper pulley with the 0° mark on the timing plate; the engine is now positioned on the No. 4 firing position. This time the No. 4 cylinder valves remain closed as the timing mark approaches the scale. Adjust the exhaust valves of cylinders No. 2, 3 and 4 and the intake valves of cylinders No. 4, 5 and 6, by performing the following procedures:

    1. Back out the adjusting nut until lash can be felt at the pushrod.

    2. While rotating the pushrod, turn the adjusting nut inward until all of the lash is removed.

    3. When the play has disappeared, turn the adjusting nut inward 1 additional turn for 1988-93 engines or 13/4 additional turns for 1994 engines.

  3. Install the rocker arm covers.

  4. Connect the negative battery cable, then run the engine and verify there are not leaks.

  5. Shut the engine OFF, then install the engine cover. You may wish to allow the engine to cool first as you may be working near HOT components.

KMP1171, ASE Certified Technician
Category: Chevy
Satisfied Customers: 224
Experience: Mech for 20yrs and GM Specific for 15
KMP1171 and 5 other Chevy Specialists are ready to help you
Expert:  KMP1171 replied 4 years ago.
When at TDC of #1 CYL the rotor should be at #1 on cap.
Customer: replied 4 years ago.

it is a 1995 chev astro van W not a Z

Customer: replied 4 years ago.

 

My computer crashed sorry! now my 1995 astro van is two wheel dr whivh I beleive is w and the information you sent was for 1993 and 1994 is this the same ,also it is not for type z infor I need thanks

Expert:  KMP1171 replied 4 years ago.
The info still applies to the w except that the valves rockers are torque to spec and are not adjustable. But TDC and rotor position and valve position is same.

VIN W

The 4.3L (VIN W) engine and some of the 4.3L (VIN Z) engines are equipped with screw-in type rocker arm studs with positive stop shoulders. Because the shoulders allow the rocker arms to be torqued into proper position, no adjustments are necessary or possible. If a valve train problem is suspected, check that the rocker arm nuts are tightened to 20 ft. lbs. (27 Nm). When valve lash falls out of specification (valve tap is heard), replace the rocker arm, pushrod and hydraulic lifter on the offending cylinder.

Customer: replied 4 years ago.

 

 

thanks very much for your patients

Expert:  KMP1171 replied 4 years ago.
Is the info what you needed or do you need more Let me know I am here.

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