Are 327 and 350 the same bore?
The short answer: yes. In the most common Chevrolet small-block configurations, the bore is the same for both the 327 and the 350—4.000 inches—while the difference in displacement comes from the stroke.
In more detail, the bore is the cylinder’s internal diameter, and for these engines GM typically used a 4.000-inch bore on the stock blocks. The 327 achieves its 327 cubic inches primarily through a shorter stroke (about 3.25 inches), whereas the 350 uses a longer stroke (about 3.48 inches). This means two engines can share the same bore size but produce different overall displacements because of the stroke. It's worth noting that some rare production variants or aftermarket blocks may diverge from the standard bore, so always verify the exact bore on a given block when sourcing parts.
Are the bores the same across the 327 and 350?
Below is a concise side-by-side look at how bore and related dimensions typically compare between these two engines.
- Common bore size: 4.000 inches for both the 327 and the 350 in the stock Gen I small-block blocks.
- Stroke difference: 327 uses about 3.25 inches; 350 uses about 3.48 inches.
- Displacement impact: 327 ≈ 327 cubic inches; 350 ≈ 350 cubic inches, driven by the stroke rather than a bigger bore.
- Variations: Some engines or aftermarket blocks may have different bore sizes, so always check the specific block’s bore measurement.
In short, the bore is typically identical for these two engines, and the larger displacement of the 350 comes from a longer stroke rather than a bigger cylinder diameter. When rebuilding or swapping parts, verify the exact bore on the block to ensure correct fitment of sleeves, pistons, and heads.
Additional considerations: interchangeability and build planning
Even with the same bore, interchangeability is not guaranteed. Other dimensions—such as deck height, crankshaft journal sizes, rod lengths, piston compression heights, and head bolt patterns—also influence compatibility and performance. If you’re assembling or upgrading an engine, align the crank, pistons, rods, and heads to achieve the target displacement and to ensure proper sealing and reliability.
Practical tips for builders
- Always measure the actual bore on the block with a bore gauge before ordering sleeves or pistons.
- If you’re aiming for a specific displacement (327 vs 350), plan around stroke and piston/rod combinations in addition to bore size.
Summary
The common Gen I Chevrolet small-block practice is that the bore (cylinder diameter) is the same—4.000 inches—for both the 327 and 350. The key distinction is the stroke, which yields the difference in total displacement. Always verify the exact bore on your specific block, especially with used cores or aftermarket variants, and plan parts accordingly to ensure proper fit and performance.
Are 350 and 327 pistons the same?
No, 327 and 350 pistons are not the same because of their differing wrist pin heights, which are designed to compensate for the difference in stroke between the two engines. While both engines share the same 4-inch bore diameter, the 350 has a longer stroke (3.483.483.48 inches) than the 327 (3.253.253.25 inches). This means that using the wrong piston will result in either the piston sitting too low in the cylinder or causing it to collide with the head.
- Same bore, different stroke: Both the 327 and 350 Chevy small-block engines have a 4-inch bore, but the 350 has a longer stroke.
- Different pin height: To accommodate the difference in stroke, the pistons for the 327 and 350 have different wrist pin heights.
- Incorrect piston leads to problems:
- If you put a 350 piston in a 327 block, the piston would be too low in the cylinder, leading to a low compression ratio.
- If you put a 327 piston in a 350 block, the piston would be too high and collide with the cylinder head.
- Key takeaway: Because of the different wrist pin heights, you cannot use 327 pistons in a 350 engine, or vice-versa, without causing major engine problems.
What is the bore size of the 327?
The Chevy 327 engine has a standard bore size of 4.00 inches (101.6101.6101.6 mm). This is combined with a 3.25-inch (82.5582.5582.55 mm) stroke, which is what distinguishes it from the 350 engine, which has a 4-inch bore but a longer 3.48-inch stroke.
- Bore: 4.00 inches (101.6101.6101.6 mm)
- Stroke: 3.25 inches (82.5582.5582.55 mm)
- Distinguishing Feature: The 327's relatively short stroke is a key difference between it and the 350, a popular misconception is that they both have the same bore, but the 350 is 4 inches and the 327 is 3.48 inches.
Is a 327 the same bore as a 350?
Both the 327 and 350 have 4" bores.
Can I put a 327 crank in a 350 block?
Yes, a 327 crank can be put in a 350 block, but only if it's a large journal 327 crank (from a 1968-1969 model year). You will also need to use 327 pistons and connecting rods to ensure proper compression and fit.
This video explains the difference between a 327 and 350 crankshaft: 59sRust Bros (Official) YouTube · Nov 10, 2024
What to know
- Engine displacement: With a 327 crank, rods, and pistons in a 350 block, the engine will have a smaller displacement than a standard 350.
- Piston selection: You cannot use 350 pistons with a 327 crank because the stroke and wrist pin height will be different, which will cause problems with compression and fit.
- Rod length: Both the 327 and 350 use the same 5.7-inch connecting rods.
- Journal size: The key difference is that the 1968-69 large journal 327 has the same main journal diameter as a 350, but the smaller journal 327 (from 1962-1967) will not work with a 350 block.
