Reasons to consider head shaving:
* High mileage/wear: If the engine has high mileage or shows signs of significant wear (like excessive oil consumption or overheating), a head gasket leak might be present, or the head itself may be warped. Shaving the head can correct a slight warp and provide a better seal for the new head gasket. However, excessive shaving reduces the compression chamber volume, potentially leading to higher compression and increased risk of detonation. A professional machinist should assess this.
* Head gasket failure (if replacing the head gasket): If the head gasket failed, the head should be checked for warping before reinstalling it. A warped head will cause the same problems you were trying to solve.
* Performance enhancement (rare and not recommended for this application): Shaving the head *slightly* can slightly increase compression ratio, boosting performance, but it's a marginal gain in a naturally aspirated 4-cylinder and should only be done by someone experienced and with careful measurement. This is usually not worth the risk for a standard replacement.
Other things to consider while the engine is out:
* New Head Gasket: Always replace the head gasket, regardless of whether you shave the head or not. This is a critical seal and a new one is cheap insurance.
* Inspect the Head: Thoroughly inspect the cylinder head for cracks, damage, or signs of overheating.
* Valve Job: Depending on the engine's condition, a valve job (lapping, grinding, and replacing valve seals) may be needed for optimal performance. This is recommended if the head has been off and there are issues.
* Timing Chain/Belt: Inspect and replace if worn or showing signs of wear.
* Water Pump: A new water pump is a very good investment while the engine is out - it's much easier to access and replace.
* Timing components: Check the timing chain tensioner, guides and sprockets.
* Oil pump: This isn't always a must-do, but an inspection is worthwhile. If suspect, it's far easier to change now than ever.
* Clean the engine block: Thoroughly clean the engine block. This improves visual inspection.
In short: Unless you have a specific reason (like a known warped head or persistent overheating), shaving the head is *not* typically necessary during a simple engine replacement in a 2001 S10. Focus on replacing worn parts and ensuring a proper seal with a new head gasket. Have a professional machine shop check the head for warpage if you're unsure. They can tell you if shaving is necessary or if other issues need to be addressed.
