Are a 327 and 350 block the same?
Not exactly. The 327 and 350 blocks are both generations of Chevrolet’s small-block V8, but they are not identical blocks. The primary difference is the stroke, which makes the engines displace 327 and 350 cubic inches respectively. They share many design traits and mounting points, so parts can be interchanged in many cases, but internal clearances and specific component choices matter for reliable performance.
To understand how these blocks relate, it helps to look at what they have in common, what sets them apart, and what this means for someone building or restoring a Chevy small-block. The following sections break down the similarities, the key differences, and practical considerations for builders and enthusiasts.
Similarities between the 327 and 350 blocks
The following points describe aspects the blocks share that often surprise people who are new to small-block Chevy builds.
- They belong to Chevrolet’s Gen I small-block family, sharing the same basic architecture and mounting interfaces.
- Both commonly use a 4.000 inch bore, and they share the same overall exterior dimensions and gasket surfaces, which helps with compatibility of many parts.
- Intake manifolds, cylinder heads, front covers, timing covers, water pumps, and most accessory fittings are designed to fit both blocks, making swaps and upgrades feasible in many builds.
- Front timing cover alignment, oil pan rails, and distributor locations are generally compatible, which simplifies upgrading or rebuilding using parts from either engine family.
These shared traits mean that, on the surface, the 327 and 350 blocks are quite interchangeable for many standard parts and common maintenance tasks. The real differences come down to the internals and the resulting engine displacement.
Differences to consider when comparing or building
The most impactful differences lie in the engine’s internal dimensions and resulting displacement, which affect everything from crank and piston choices to clearance and performance potential.
- The primary engineering difference is the stroke: 327 uses a shorter stroke (about 3.25 inches), while 350 uses a longer stroke (about 3.48 inches).
- Displacement follows the stroke difference: 327 blocks are built for roughly 327 cubic inches, while 350 blocks yield about 350 cubic inches, assuming standard bore sizes and piston configurations.
- Piston and rod considerations: To change displacement or achieve a stroked setup, you must select pistons with the correct compression height and dish/valve clearance, and you may need to match rods appropriately for the chosen crank.
- Crankshaft compatibility: A 350 crank can be used in a 327 block to create a stroked engine, which is a common practice for sleepers or mild performance builds. Conversely, dropping a 327 crank into a 350 block is generally less common, as it reduces displacement unless other changes are made.
- Block reliability and mains: Both families offer 2-bolt and 4-bolt main variants, but for higher-performance or stroker applications, many builders prefer a block with robust main bearing support. Always verify the specific casting and configuration of the block you’re using.
- Casting numbers and identification: Casting numbers differ between factory 327 and 350 blocks; if you’re restoring or sourcing a block, check the casting code to confirm which block you have and whether it matches your intended build.
In practical terms, these differences mean you can often achieve a stroked or boosted setup by pairing a 350 crank with a 327 block, but you must account for piston clearance, rod length, and potential valvetrain or oiling considerations. A direct one-to-one swap of blocks to change displacement isn’t a straightforward drop-in; it requires engineering checks and precise component selection.
Practical build notes
If you’re planning a build or restoration, here are actionable takeaways to keep in mind when dealing with 327 and 350 blocks.
- Confirm bore and stroke combinations before buying pistons or cranks. A 4.000 inch bore is common, but you must verify the exact block specs for your build.
- Consider stroking a 327 by using a 350 crank in the block to reach roughly 355–360 cubic inches, with appropriate pistons and rods to maintain proper clearance and compression.
- When choosing heads and intake, expect broad compatibility across both blocks, but re-check chamber volume, combustion chamber shape, and valve clearance for your specific pistons and camshaft choice.
- Check the block’s main-cap configuration (2-bolt vs 4-bolt) and oiling passages, especially if you plan higher-performance or boosted applications.
- Always verify a casting number and consult a machinist or engine builder. Subtle differences in casting revisions can affect deck height, oil passages, and overall fitment of internal components.
By paying attention to these details, you can maximize compatibility and performance when working with 327 and 350 blocks, whether you’re restoring a classic hot rod or building a modern-stroker for fun on the street.
Summary
The 327 and 350 blocks are not the same, but they are closely related. They share the same family, external dimensions, and many compatible parts, with the key difference being stroke, which determines displacement and affects build choices. A common approach is to stroke a 327 with a 350 crank to approach the 355–360 cid range, though it requires careful piston, rod, and clearance planning. For accurate results, always check casting numbers, consult a machinist, and verify fitment for your specific combination.
Can I put a 350 crank in a 327?
Yes, a 350 crank can be put in a 327 block, but you must first verify that the 327 is a "large journal" block from 1968 or later, as the smaller "small journal" blocks will have incompatible bearings. When using a 350 crank in a 327 block, the longer stroke requires using 350 rods and pistons to ensure clearance between the piston and the cylinder head, block, and valves. The result will essentially be a 350ci engine, which is often done to create more torque.
This video explains the differences between Chevy 350 and 400 engines, including stroke and bore size: 57sMyvintageiron7512YouTube · Feb 12, 2023
Before you begin
- Identify your 327 block: Check if it's a "small journal" (1967 and earlier) or "large journal" (1968 and later) block. The "large journal" block has the same bearing sizes as a 350 and is the only one compatible with a 350 crank.
- Determine compatibility: The 350 crank will fit the main bearing saddles of a large journal 327 block, but the longer stroke will cause clearance issues with the original 327 pistons.
What you will need to do
- Install the 350 crankshaft: into the 327 block.
- Use 350 connecting rods: to maintain the correct rod length and geometry.
- Use 350 pistons: to ensure the piston doesn't hit the cylinder head or valves when the crank rotates. The 350 crank has a longer stroke, which means the piston travels further. Without different pistons, there will be interference.
- Check all clearances: It is critical to verify all clearances, including piston-to-valve, piston-to-head, and piston-to-block, after assembly.
- Assemble the engine: The resulting engine will have a 350 cubic inch displacement and will require 350 rods and pistons to work correctly.
Is a 350 bored 30% over a 383?
Yes, a 350 bored .030 over, combined with a 3.75-inch stroke crankshaft from a Chevy 400, creates a 383 cubic inch stroker engine. Boring the 350 block to a final bore diameter of 4.030 inches and adding the longer stroke results in the 383 displacement.
You can watch this video to learn how to build a Chevy 383 stroker engine: 56sThe Horsepower MonsterYouTube · Sep 11, 2024
- The build process: A 350 engine block is the base, and its cylinders are machined to a final diameter of 4.030 inches (the original 4.000-inch bore plus .030 inches). A 3.75-inch stroke crankshaft from a 400 engine is then installed, which increases the engine's displacement.
- Displacement calculation: The formula for cubic inches is approximately Bore2×Stroke×0.7854×Number of Cylinderscap B o r e squared cross cap S t r o k e cross 0.7854 cross cap N u m b e r space o f space cap C y l i n d e r s𝐵𝑜𝑟𝑒2×𝑆𝑡𝑟𝑜𝑘𝑒×0.7854×𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐶𝑦𝑙𝑖𝑛𝑑𝑒𝑟𝑠. With a 4.030-inch bore and a 3.75-inch stroke, the calculation is approximately 4.0302×3.75×0.7854×8≈382.64.030 squared cross 3.75 cross 0.7854 cross 8 is approximately equal to 382.64.0302×3.75×0.7854×8≈382.6, which is rounded up to 383 cubic inches.
- Benefits: Building a 383 stroker is a popular way to increase a small-block Chevy's power, especially torque, without having to use a larger, heavier big-block engine.
Is a 327 and a 350 the same block?
The larger sized main journal diameters of the 1968 327 small-block, 2.450, are the exact size of the later 350 small-block. The difference between the two is the length of stroke on the crank, 3.250 for the 327 and 3.484 for the 350.
What is the difference between 327 and 350 pistons?
The 327 has a 3.25-inch stroke, while the 350 has a 3.48-inch stroke. Though both engines have a 4-inch bore and 5.7-inch connecting rods, the different crankshaft stroke results in a different piston design. The 350 has pistons with a slightly raised pin to compensate for the longer stroke.
