A 350 long block is a complete engine assembly minus the external accessories

A 350 long block is a Chevrolet 350 cubic-inch V8 engine that includes the block, heads, crankshaft, pistons, and internal gaskets — but not the carburetor, intake manifold, alternator, water pump, or other bolt-on parts. You receive the core engine ready to bolt into an engine bay, but you will need to transfer or purchase the external components separately.

The term "long block" distinguishes it from a "short block," which contains only the block, crankshaft, and pistons without the cylinder heads. It also differs from a "crate engine," which arrives fully assembled with all accessories included and ready to run. Understanding which version you need depends on what parts you already have and how much work you want to do yourself.

The 350 long block became popular because the 350 engine itself was produced from 1967 through the early 2000s in various Chevrolet vehicles, trucks, and marine applications. This long production run means used and rebuilt 350 long blocks remain widely available, and many people already own the accessories needed to complete one.

Key Takeaways

  • A 350 long block includes the engine block, cylinder heads, crankshaft, and pistons but requires you to source or transfer the carburetor, intake manifold, alternator, water pump, and other external parts.
  • The cost of a 350 long block varies significantly depending on whether it is used, rebuilt, or new, and whether the internal components are original or performance-upgraded.
  • Installing a 350 long block requires mechanical skill, proper tools, and knowledge of engine mounting, cooling system connections, and fuel and ignition system routing.
  • A long block is less expensive than a complete crate engine but requires more work and planning than buying a fully assembled engine ready to start.

What components come inside a 350 long block

The internal parts of a 350 long block include the cast-iron engine block with all cylinder bores, the cylinder heads with valves and valve springs, the crankshaft, connecting rods, pistons and rings, and the internal gaskets and seals. The oil pan is sometimes included, though some sellers remove it to reduce shipping weight. The timing cover and timing chain or gear are typically included as part of the block assembly.

What you do not receive are the external accessories: the carburetor or fuel injection system, the intake and exhaust manifolds, the alternator, the water pump, the thermostat housing, the starter motor, the air cleaner, the spark plug wires or coils, and the engine mounts. You will need to either transfer these parts from your old engine or purchase them separately. If you are replacing an engine in an existing vehicle, you can often reuse these components from the original engine, which saves money.

Some 350 long blocks are sold as "dressed" long blocks, meaning they include the intake manifold, water pump, and thermostat housing already bolted on. This reduces the number of parts you need to source but increases the price. Always confirm with the seller exactly which components are included before purchasing.

New, rebuilt, and used 350 long blocks have different costs and reliability profiles

A new 350 long block from a manufacturer or authorized dealer costs significantly more than rebuilt or used options but arrives with a warranty and known internal specifications. New blocks are rare because the 350 has not been produced by Chevrolet since the early 2000s, so "new" typically means a recently manufactured reproduction or a dealer overstock part. Expect to pay premium prices for this option.

A rebuilt 350 long block has been disassembled, inspected, and reassembled with new or reconditioned internal parts. The block itself is bored and honed, the crankshaft is ground, and new pistons, rings, bearings, and gaskets are installed. Rebuilt blocks usually come with a warranty ranging from 12 months to 3 years, depending on the rebuilder. This is the middle-ground option: more reliable than used, less expensive than new.

A used 350 long block is pulled from a salvage vehicle or removed from a running engine and sold as-is, often with no warranty. The internal condition is unknown unless the seller has run a compression test or borescope inspection. Used blocks are the cheapest option but carry the highest risk of hidden damage, wear, or internal problems that only show up after installation and startup.

Installation requires engine bay space, cooling system connections, and fuel routing

Installing a 350 long block is not a bolt-in-and-go process. You will need to drain the coolant from your existing engine, disconnect the fuel lines, remove the spark plug wires or coil packs, unbolt the engine mounts, and remove the old engine using an engine hoist. The new long block then goes in the same location, but you must reconnect every external system: the cooling hoses to the water pump, the fuel lines to the carburetor or fuel rail, the ignition wires or coils to the spark plugs, and the alternator output to the battery.

The engine mounts must align with the block's mounting points. If you are installing a 350 into a vehicle that originally had a different engine, you may need custom engine mounts or adapter plates. The exhaust manifolds must fit inside the engine bay without hitting the frame or suspension, and the intake manifold must clear the hood. These clearance issues are common when swapping engines into older vehicles or non-original applications.

You will also need to verify that your radiator, cooling fan, and hoses are compatible with the 350's cooling requirements. A long block alone does not include a radiator or cooling fan, so you must either reuse the existing cooling system or upgrade it if the original was sized for a smaller engine. Improper cooling is one of the most common reasons a newly installed engine overheats.

A 350 long block costs less than a crate engine but more than a short block

The price difference between engine options reflects how much assembly work is already done. A short block (block, crankshaft, pistons, and rods only) costs the least because it requires you to source and install the cylinder heads, intake manifold, and all external accessories yourself. A 350 long block costs more because the heads are already installed, but less than a crate engine because you still need to add the carburetor, alternator, water pump, and other bolt-ons.

A complete crate engine costs the most because it arrives fully assembled, primed, and ready to bolt in and start. You straightforward connect the fuel line, ignition wires, and cooling hoses. For someone without machine shop access or mechanical experience, a crate engine eliminates the risk of mismatched parts or incomplete assembly. For someone with spare parts on hand or mechanical skill, a long block offers a middle path between cost and convenience.

Pricing varies widely by region, seller, and engine condition. A used 350 long block might range from $500 to $1,500, a rebuilt block from $1,500 to $3,500, and a new or reproduction block from $3,500 and up. Always get a written description of what is included and what warranty, if any, is offered before committing to a purchase.

Matching the 350 to your vehicle's original engine size matters for cooling and fuel systems

If your vehicle originally had a 350, installation is straightforward because all systems are already sized for that engine. The radiator, water pump, fuel pump, alternator output, and engine bay space are all matched to the 350's specifications. You can reuse most or all of the existing external components, which reduces both cost and complexity.

If you are installing a 350 into a vehicle that originally had a smaller engine, you may need to upgrade the cooling system, fuel pump, and electrical charging system. A smaller radiator will not dissipate enough heat from a 350, and a fuel pump designed for a 250 cubic-inch engine may not deliver enough volume. An undersized alternator will not keep the battery charged under load. These upgrades add cost and labor but are necessary to prevent overheating, fuel starvation, or electrical problems.

If you are installing a 350 into a vehicle that originally had a larger engine, the existing systems may be oversized but usually still functional. A radiator designed for a 454 will cool a 350 without issue. However, you must still verify that the 350's mounting points align with the engine bay and that the intake and exhaust manifolds fit without interference.

Frequently Asked Questions

Can I install a 350 long block myself if I have never rebuilt an engine before?

You can if you have access to an engine hoist, jack stands, and basic hand tools, and if you take time to understand the cooling, fuel, and ignition system routing for your specific vehicle. Many people complete their first engine installation by following a shop manual and taking photos of the old engine before removal. However, mistakes in coolant connections or ignition timing can cause overheating or no-start conditions, so consider having a mechanic review your work before starting the engine.

What is the difference between a 350 long block and a 350 crate engine?

A crate engine includes the carburetor, intake manifold, alternator, water pump, and all other external accessories, and arrives fully assembled and ready to bolt in. A long block includes only the block, heads, crankshaft, and pistons, so you must source or transfer the external parts yourself. A crate engine costs more but requires less labor and planning.

Do I need to change the oil and coolant when ready after installing a new 350 long block?

Yes. Before starting the engine, fill the cooling system with the correct coolant mixture and verify that all hose connections are tight. Run the engine briefly to circulate coolant and check for leaks, then drain and refill the oil after the first 50 miles of driving. New or rebuilt engines may have metal particles from the manufacturing or rebuilding process, so an early oil change removes these contaminants.

What should I do if the 350 long block does not fit in my engine bay?

Check that the engine mounts are correctly positioned and that the intake and exhaust manifolds are the right style for your vehicle. Some manifolds are taller or wider than others. If clearance is still an issue, you may need custom engine mounts, a different intake manifold, or headers instead of cast-iron manifolds. A mechanic familiar with engine swaps in your vehicle type can advise on the best solution.

Is a used 350 long block worth the risk compared to a rebuilt one?

A used block is worth considering if the seller can provide a compression test showing all cylinders within 10 percent of each other, or if the engine was recently running in a known vehicle. If the history is unknown, a rebuilt block with a warranty offers more peace of mind, especially if you are paying for installation labor. The cost difference between used and rebuilt is often small enough that the warranty justifies the upgrade.