How do I perform a DIY LS7 wiggle test on a Chevrolet Corvette C6 Z06?

Performing a wiggle test on the LS7 is a necessary rite of passage for C6 Z06 owners to check for premature valve guide wear. This is a Moderate to Hard job depending on your experience with valvetrain work. You are dealing with compressed springs and the risk of dropping a valve into a cylinder, so take your time.

Here is the procedure based on enthusiast consensus and standard LS valvetrain practices.

Tools Required

• Comp Cams LS7 valve spring removal tool
• Spark plug air hold hose (threads into the plug hole)
• Air compressor (90-100 psi)
• Dial indicator with a flexible/snake stand (a vice-grip base from Matco or Snap-on works best here)
• 3/4" socket and a hammer
• Small pieces of rubber hose (used as valve keepers)
• 10mm and 8mm sockets
• Pick tool or small flathead screwdriver
• Pen magnet
• Valvetrain organizer tray
• Inch-pound and foot-pound torque wrenches ⁴

1. Prep and Teardown

First, put the transmission in Neutral and throw some fender covers on to protect your paint.

1. Remove the plastic engine covers.
2. Remove the spark plug wires by sliding them off the coil first, then wiggling the rubber boot off the plug. Do not pull on the wire itself.
3. Disconnect the main coil pack wiring harness (the large cream-colored connector) and use a 10mm socket to remove the five bolts holding the coil bracket to the valve cover.
4. Unclip the front PCV hose from the valve cover using a pick to slide the retaining tab out of the way, then pull it gently.
5. Use an 8mm socket to remove the four valve cover bolts and pull the covers.
6. Remove the spark plugs.
7. Unbolt and remove your rocker arms and pushrods. Keep these strictly organized. They must go back into the exact same positions they came from (lifter side to lifter side, rocker to rocker).
8. Use your pen magnet to pull the intake valve lash caps straight up and off ⁴.

2. Removing the Valve Springs

You need to keep the valves from dropping into the cylinder when the springs are removed.

1. Thread your air hose tool into the spark plug hole of your first cylinder.
2. Connect shop air (90-100 psi). Warning: You will hear the engine turn over as the air pressure pushes the piston down to the bottom of its stroke.
3. Once the piston is down, temporarily disconnect the shop air to depressurize the cylinder.
4. Place your 3/4" socket over the valve retainer and give it a light tap with your hammer. This breaks the stiction on the valve locks so they don't fight you when you compress the spring.
5. Reconnect the shop air.
6. Bolt down your Comp Cams spring compressor and compress the spring just enough to free the locks. Use your pen magnet to grab the locks out of the retainer.
7. Back the compressor off, remove the spring, and place it in your organizer.
8. Slide one of your cut pieces of rubber hose tightly over the valve stem. This acts as a safety stop so the valve can't fall into the engine. You can now disconnect the shop air ⁴.

3. The Wiggle Test

With the spring off and the valve resting on the seat, you can now measure the guide clearance.

1. Mount your dial indicator base securely to the cylinder head.
2. Position the tip of the dial indicator against the valve stem, just above the valve guide ⁴.

The following steps rely on standard engine building procedures, as the forum guide cuts off here: 3. Push the valve stem firmly side-to-side in the direction that the rocker arm sweeps (parallel to the rocker body). 4. Read the total sweep on the dial indicator.

Specs: The widely accepted GM service limit for both intake and exhaust valve guide clearance on the LS7 is 0.0037 inches. If your total dial indicator sweep exceeds this, your guides are out of spec and the heads need to be rebuilt or replaced. Keep in mind that measuring further up the valve stem amplifies the reading due to geometry, so checking the GM Factory Service Manual for the exact measurement height and calculation multiplier is highly recommended to avoid a false positive.

4. Reassembly

Reassembly is the reverse of removal. I don't have verified torque figures for the LS7 rocker arm bolts or valve covers in the provided context, so don't take a number from me on it—check your factory service manual. The procedure itself requires making sure the lifter is on the base circle of the camshaft before torquing the rocker arms down, cleaning the valve cover mating surfaces, and using your foot-pound and inch-pound torque wrenches to bring everything back to factory spec.