A 383 short block is an engine core without the cylinder head, intake manifold, or external accessories
A short block is the lower half of an engine — the block itself, the crankshaft, pistons, connecting rods, and oil pan. A 383 refers to the engine's displacement, which is 383 cubic inches. When you buy a 383 short block, you are buying the foundation of the engine, but you will need to add the top end (cylinder head, valves, spark plugs) and bolt on the accessories (alternator, water pump, air cleaner) yourself or have a mechanic do it.
The 383 is a common engine size in hot rodding and engine rebuilding because it sits between the smaller 350 cubic inch engine and the larger 427 or 454. It offers more power than a stock 350 without the extreme cost or complexity of a big-block engine. Most 383 short blocks are built by boring out a 350 block (increasing the cylinder diameter) and installing a longer stroke crankshaft, which increases total displacement.
Key Takeaways
- A short block includes the engine block, crankshaft, pistons, and connecting rods, but not the cylinder head or external parts like the alternator or water pump.
- The 383 displacement means the engine moves 383 cubic inches of air and fuel through its cylinders per complete cycle.
- A 383 short block requires you to source and install a cylinder head, intake manifold, and all external accessories before the engine can run.
- Short blocks are sold as bare cores, partially assembled, or fully assembled depending on the builder and price point.
- Buying a short block costs less than buying a complete crate engine, but requires more work and knowledge to finish the build.
Short block versus long block versus crate engine
The terms describe how much of the engine is already assembled when you receive it. A short block is the bare lower half — block, crankshaft, pistons, rods, and oil pan. A long block adds the cylinder head, valves, and valve train on top, so it is ready to bolt into the engine bay once you add the external parts (alternator, water pump, power steering pump, air cleaner, intake manifold). A crate engine is a complete, ready-to-run engine that includes everything except the transmission and engine mounts; you bolt it in and connect fuel, ignition, and cooling lines.
The cost difference is significant. A 383 short block might cost $1,500 to $3,500 depending on the builder and how much machine work is included. A long block adds $1,000 to $2,000. A complete crate engine can run $4,000 to $8,000 or more. The trade-off is labor: a short block requires the most assembly time and knowledge, while a crate engine is fastest to install but most expensive upfront.
What machine work is usually included in a short block
Most 383 short blocks sold by reputable builders include the core machine work: the block has been bored to the correct diameter, the crankshaft has been ground to specification, and the pistons and rods have been balanced together. The block is usually honed (the cylinder walls are finished with a crosshatch pattern to help the piston rings seat), and the main bearing surfaces have been checked and finished.
What is not usually included depends on the price tier. Budget short blocks may come with used pistons and rods; mid-range blocks often include new pistons and rods but used crankshafts; premium blocks include new or fully reconditioned parts throughout. Before you order, ask the builder exactly what is new, what is reconditioned, and what is used. Also ask whether the block has been pressure-tested (to check for cracks) and whether the crankshaft has been magnafluxed (a test for hidden cracks in the metal).
What you need to add to make a 383 short block run
After you receive the short block, you must source and install a cylinder head. The head bolts to the top of the block and contains the valves, spark plug holes, and intake and exhaust ports. You will also need an intake manifold (which bolts to the head and directs the air-fuel mixture into the cylinders), a carburetor or fuel injection system, an ignition system, and external accessories: alternator, water pump, power steering pump (if equipped), air cleaner, and exhaust manifolds or headers.
You will also need gaskets, seals, bolts, and coolant hoses. Many builders sell a "gasket set" for a 383, which includes all the gaskets you will need between the block, head, intake, and oil pan. The cylinder head alone can cost $500 to $2,000 depending on whether it is used, reconditioned, or new, and whether it is ported and polished (modified for better airflow). The total cost to finish a 383 short block into a running engine typically ranges from $3,000 to $6,000 or more, depending on the quality of parts you choose.
Where to buy a 383 short block
383 short blocks are sold by engine machine shops, hot rod suppliers, and online retailers that specialize in engine parts. Local machine shops often build them to order and can customize the parts inside (piston type, rod length, crankshaft finish). National suppliers like Summit Racing, Jegs, and Speedway Motors stock pre-built short blocks from established builders. eBay and Craigslist sometimes have used short blocks, but buying used carries the risk that you cannot verify the machine work or the condition of internal parts without disassembly.
When shopping, compare not just price but also what is included, what warranty (if any) is offered, and the builder's reputation. Ask whether the short block has been run-tested or only pressure-tested. Some builders offer a "turn-key" short block that includes the cylinder head and intake manifold, which reduces the assembly work you need to do yourself.
Common reasons to buy a 383 short block
The 383 is popular in hot rodding because it delivers noticeable power gains over a stock 350 without requiring a complete engine redesign. It fits in the same engine bay as a 350, uses the same bolt patterns and mounts, and works with existing cooling and fuel systems in many cases. For someone rebuilding a classic car or truck, a 383 short block offers a straightforward path to more horsepower without the cost or complexity of a big-block swap.
Builders also choose the 383 because it is a known quantity — parts are widely available, machine shops know how to build them, and there is a large community of people who have done it before. If something goes wrong during assembly, you can post a question online and get answers from people who have built dozens of them.
Frequently Asked Questions
How much horsepower does a 383 short block make?
That depends entirely on the cylinder head, intake manifold, carburetor or fuel injection, and ignition system you bolt on top. A basic 383 with a stock head and carburetor might make 350 to 400 horsepower. A 383 with a high-flow head, performance intake, and tuned fuel injection can exceed 450 horsepower. The short block itself is just the foundation.
Can I use a 383 short block in my truck or car?
Yes, if the engine bay has room and the mounting points match. A 383 uses the same block as a 350, so it bolts into any engine bay that originally held a 350 or 305 Chevrolet engine. You will need to verify that your cooling system, fuel system, and wiring can handle the engine before you start assembly.
Do I need special tools to assemble a 383 short block?
You need basic hand tools (wrenches, sockets, screwdrivers) and a torque wrench to tighten bolts to the correct specification. You will also need a gasket scraper, a hoist or engine stand to hold the block, and access to a work surface. If you are not comfortable working on engines, hiring a machine shop or mechanic to do the assembly is a reasonable choice.
What is the difference between a 383 and a 350?
The 383 has a larger bore (cylinder diameter) and longer stroke (piston travel distance), which increases displacement from 350 to 383 cubic inches. More displacement means more air and fuel per cycle, which typically results in more power. A 383 is heavier and requires more fuel, but delivers noticeably stronger acceleration.
How long does it take to assemble a 383 short block into a running engine?
If you are experienced, 40 to 60 hours of work is typical. If you are learning as you go, add another 20 to 40 hours. A professional machine shop can usually finish the job in one to two weeks, depending on their workload. The cylinder head installation and tuning of the fuel and ignition systems usually take the most time.