A 350 small block rebuild kit contains the internal engine parts that wear out over time, but not the external components, machine work, or specialty tools you'll need to complete the job

A 350 small block rebuild kit is a packaged set of internal engine components designed for the Chevrolet 350 cubic-inch V8 engine. The kit typically includes pistons, rings, bearings, gaskets, and seals — the parts that experience the most wear and tear during normal engine operation. What it does not include is equally important: cylinder boring, valve work, the block itself, the crankshaft, the cylinder head, or any external parts like the water pump, alternator, or intake manifold.

The purpose of a rebuild kit is to give you a starting point and save money by bundling the most commonly replaced internal parts. However, calling it a "complete" kit is misleading. Most rebuilds require additional purchases, machine shop services, and decisions about whether to reuse or replace components the kit doesn't cover.

Key Takeaways

  • A standard 350 rebuild kit includes pistons, rings, bearings, gaskets, and seals, but the block, crankshaft, and cylinder head are sold separately or assumed to be reused.
  • Machine shop work — boring cylinders, honing, line boring the block, and valve work on the head — is not included in the kit price and often costs as much as the kit itself.
  • Kit quality varies widely by manufacturer; Sealed Power, Mahle, and Clevite are common OEM-sourced options, while cheaper kits may have lower tolerances or inconsistent quality.
  • You will need specialized tools like a ring compressor, piston pin removal tool, and torque wrench; many shops rent or loan these rather than requiring purchase.
  • The decision to rebuild versus replace the block, crankshaft, or head depends on their condition, which you won't know until the engine is disassembled and inspected.

What's Actually in a Standard 350 Rebuild Kit

A typical 350 rebuild kit from suppliers like Sealed Power, Mahle, or Clevite includes pistons with wrist pins, piston rings (compression and oil control rings), connecting rod bearings, main bearings, gasket sets for the block, valve cover gaskets, oil pan gasket, timing cover gasket, and often a rear main seal. Some kits add a water pump gasket or freeze plug set. The exact contents vary by kit grade and manufacturer.

The kit does not include the block itself, crankshaft, connecting rods, cylinder head, valves, valve springs, camshaft, timing chain or belt, oil pump, water pump, alternator, starter, carburetor or fuel injection components, intake or exhaust manifolds, or any external hardware. These are either reused from your existing engine or purchased separately.

Kit pricing typically ranges from $200 to $600 depending on piston quality, bearing material, and what gaskets are bundled. A "premium" or "performance" kit with forged pistons and higher-quality bearings costs more than a standard replacement kit with cast pistons.

Machine Shop Work That's Not in the Kit

Before you can install the new pistons and rings, the block must be bored and honed if the cylinders are worn, scored, or out of round. Boring enlarges the cylinder diameter to accept oversized pistons; honing creates the proper surface finish for the rings to seal. A machine shop performs this work, and it typically costs $75 to $150 per cylinder, or $600 to $1,200 for all eight cylinders on a 350.

The crankshaft must be inspected for wear and may need grinding to a smaller diameter if the main or rod journals are damaged. A crankshaft grind costs $300 to $600 and requires the crank to be balanced afterward. If the crank is cracked or too worn to grind, replacement costs $400 to $800 for a used or remanufactured unit.

The cylinder head typically needs valve work: the valves are removed, the seats are cut or replaced, the guides are checked, and the head is pressure-tested for cracks. Valve work on a 350 head runs $300 to $600. If the head has cracks that cannot be welded, a replacement head costs $400 to $1,000 depending on whether it's used, remanufactured, or new.

Line boring — aligning the main bearing bores in the block — is necessary if the block has been bored before or if the main journals show wear. This costs $200 to $400 and is often discovered only after disassembly.

Deciding What to Reuse and What to Replace

The block, crankshaft, and cylinder head are the most expensive components to replace, so most rebuilds attempt to reuse them if they're in acceptable condition. However, you won't know their condition until the engine is torn down. A machine shop inspection after disassembly typically costs $50 to $150 and tells you whether the block can be bored, the crank can be ground, and the head can be valve-worked or needs replacement.

If the block has deep scoring, cracks, or stripped bolt holes, replacement is necessary. A used 350 block costs $300 to $600; a remanufactured block costs $800 to $1,200. If the crankshaft is cracked or too worn, replacement is the only option. If the cylinder head has cracks in the combustion chamber or valve seat area, welding may work for small cracks, but large cracks require a new head.

Some builders choose to replace the crankshaft with a stroker crank to increase displacement, or to replace the cylinder head with an aftermarket performance head. These are upgrades beyond a standard rebuild and add significant cost.

Tools and Equipment You'll Need or Rent

A complete engine rebuild requires specialized tools that most home mechanics don't own. A ring compressor ($20 to $50) compresses the piston rings so the piston fits into the cylinder. A piston pin removal tool ($30 to $100) separates the piston from the connecting rod. A torque wrench ($40 to $150) tightens bolts to the correct specification — critical for head bolts, main cap bolts, and rod bolts.

You'll also need a ridge reamer ($50 to $150) to remove the ridge at the top of the cylinder before the piston is removed, a hone ($100 to $300) to finish the cylinder after boring, and a degree wheel ($50 to $100) if you're setting valve timing. A gasket scraper and wire brush are inexpensive but essential for cleaning surfaces.

Many machine shops and tool rental companies loan or rent these tools, especially if you're having them perform the boring and honing. Some shops include tool rental in their labor cost. A full rebuild typically requires 20 to 40 hours of labor if done by a professional shop, or 40 to 80 hours if you're doing it yourself.

Kit Quality and Manufacturer Differences

Rebuild kits are not all the same. Sealed Power, Mahle, and Clevite are the most common manufacturers and supply OEM-quality parts to dealerships and machine shops. Their kits use cast or forged pistons, depending on the grade, and their bearings are made from copper-lead or tri-metal material that matches factory specifications.

Cheaper kits from less-known manufacturers may use lower-grade materials, looser tolerances, or inconsistent quality control. A piston that's slightly out of spec can cause ring blow-by or piston slap (a knocking noise). Bearings with poor material can wear prematurely. The price difference between a $250 kit and a $450 kit is usually in piston forging quality and bearing material, not in the number of parts.

If you're rebuilding an engine for daily driving, a mid-range kit from a known manufacturer is usually the best choice. If you're building a high-performance or racing engine, a premium forged-piston kit is worth the extra cost. If you're just trying to get an old engine running again at minimum cost, a budget kit may be acceptable, but expect shorter engine life.

Hidden Costs and Surprises During Disassembly

Once the engine is apart, machine shops often find problems not visible from the outside. A cracked block, a scored cylinder that's too deep to bore, a crankshaft that's cracked or too worn to grind, or a cylinder head with unrepairable cracks can add $500 to $2,000 to the total cost. Some shops include a preliminary inspection in their teardown fee; others charge separately.

Connecting rods can be bent or cracked and may need replacement ($50 to $150 per rod). The oil pump may be worn and need replacement ($100 to $300). Freeze plugs often corrode and should be replaced ($50 to $150 for all of them). The timing chain or belt may be worn and should be replaced ($100 to $300). None of these are in the rebuild kit, but all are commonly discovered during disassembly.

A realistic budget for a 350 rebuild includes the kit cost plus machine shop work, plus 20 to 30 percent contingency for unexpected repairs. A $300 kit plus $1,200 in machine work can easily become $2,000 to $2,500 once surprises are factored in.

Frequently Asked Questions

Can I use a 350 rebuild kit on a 305 or 327 engine?

No. The 350, 305, and 327 have different bore sizes and stroke lengths. A 350 piston will not fit a 305 or 327 block. However, a 350 kit can be adapted to a 400 small block with some modifications, and some builders use 350 components in stroker builds with different crankshafts. Always verify piston and bore size before purchasing.

What does "oversized pistons" mean, and do I need them?

Oversized pistons are larger in diameter and are used when the cylinder has been bored to a larger size. Standard 350 pistons are 4.000 inches; oversized pistons come in +.010, +.020, +.030, and +.040 inch sizes. You need oversized pistons only if the block has been bored. A machine shop determines the bore size after inspection and tells you which piston size to order.

Should I rebuild my 350 or just replace it with a crate engine?

A rebuild costs $1,500 to $3,000 in parts and labor and takes 4 to 8 weeks. A crate engine (new or remanufactured) costs $2,500 to $5,000 and arrives ready to bolt in. Rebuilding makes sense if the block and crankshaft are in good condition and you want to keep the original engine. A crate engine is faster and often comes with a warranty, but costs more upfront.

Do I need to replace the oil pan gasket if I'm rebuilding the engine?

Yes. The oil pan must be removed to access the crankshaft and main bearings, so the gasket is disturbed. Most rebuild kits include an oil pan gasket, but if yours doesn't, add one to your parts list. A new gasket costs $15 to $40 and prevents oil leaks after reassembly.

Can I rebuild a 350 engine myself without a machine shop?

You can disassemble and reassemble it yourself, but you cannot bore cylinders, grind a crankshaft, or valve-work a head without a machine shop. These require equipment that costs tens of thousands of dollars. Most home rebuilds involve doing the disassembly and reassembly yourself and sending the block, crank, and head to a shop for machine work.