Tools and Materials You'll Need:
* Valve adjustment tools: Specifically designed for big-block Chevys. These usually include a feeler gauge set and potentially a valve spring compressor (depending on the method used).
* Torque wrench: To properly tighten the rocker arm bolts.
* Socket set: Various sizes for the rocker arm nuts and other fasteners.
* Wrench set: For various fasteners.
* Chilton's or Haynes manual: Specific to your year and model of big-block Chevy. This is crucial for accurate torque specs and valve lash specifications.
* Timing light: For confirming proper timing after the valve adjustment.
* Shop rags: To keep things clean.
* Safety glasses and gloves: Protect yourself.
Procedure:
1. Preparation: Disconnect the battery negative terminal. Remove the valve covers. Rotate the engine using the crankshaft bolt until the timing marks align (consult your manual for the exact procedure for your engine's timing system). This ensures you're at top dead center (TDC) on the #1 cylinder compression stroke.
2. Identifying the Cylinders: Big-block Chevy cylinders are usually numbered sequentially, often starting at the front driver's side. Confirm the cylinder numbering using your manual or a diagram.
3. Checking Valve Lash: Use your feeler gauges to check the valve lash (clearance) for each valve. Your manual will specify the correct lash measurements (usually given in inches or millimeters) for both intake and exhaust valves. Remember, this is engine-specific!
* The process: With the engine at TDC on the #1 cylinder compression stroke, check the intake valve on cylinder #1. Then check the exhaust valve for cylinder #1. After checking both valves of #1, rotate the crankshaft 90 degrees clockwise and repeat the process for cylinder #7. Proceed in this manner for the remaining cylinders, rotating the crankshaft 90 degrees after checking each cylinder. This pattern is critical because only one cylinder's valves are fully closed at a time.
4. Adjusting Valve Lash: If the lash is incorrect, you'll need to adjust it. There are different ways to adjust rocker arms:
* Screw-and-nut adjustment: Some rocker arms utilize a screw and nut adjustment. Loosen the lock nut, adjust the screw until the correct feeler gauge fits snugly, then tighten the lock nut. Torque values for the lock nut are in your manual.
* Shims: Some designs utilize shims under the rocker arms, requiring removal and replacement of the shim with the correct thickness to achieve proper lash. This method is significantly more time-consuming.
5. Repeat for all Valves: Carefully check and adjust the valve lash for all intake and exhaust valves following the firing order, rotating the crankshaft 90 degrees at a time between cylinder checks.
6. Reinstallation: Once all valves are adjusted, reinstall the valve covers.
7. Verification: After reassembling, it's vital to double-check your work and ensure everything is correctly adjusted. Rotate the engine by hand several times to make sure nothing is binding. Then, start the engine and listen for any unusual noises (clicking, ticking). Use your timing light to double check your ignition timing.
Critical Considerations for 4-Bolt 7 Cam Swap:
* Cam Timing: The 4-bolt main 7 camshaft is known for its significant performance gains but requires precise cam timing. Consult your camshaft manufacturer's instructions; incorrect timing can severely damage the engine.
* Valve Springs: High-performance cams often require upgraded valve springs to handle the increased valve lift. Using stock springs could lead to valve float and damage.
* Pushrods: Check the pushrod length with the new camshaft installed to avoid valve train issues. Incorrect pushrod length can severely impact valve adjustment and cause damage.
Again, this is a complex procedure. If you lack experience, seek professional help. Improper valve adjustment can lead to severe engine damage. Always consult your engine's specific manual for correct torque specs, valve lash measurements, and other critical information.
