"It's a 350." You hear it on every used-engine listing, and it is right about as often as it is wrong. This calculator lets you settle it: measure the bore and stroke, load the numbers, and see whether the block really resolves to 349.85 cubic inches — or whether someone bored it, stroked it, or is calling a 327 a 350. Presets for the common small-blocks, big-blocks and LS engines give you a verified starting point.
The small-block truth table
Chevy small-blocks mostly share a 4.00-inch bore and differ by stroke, which is why the badges cluster so tightly. Here is what the geometry actually gives:
| Engine (nominal) | Bore in | Stroke in | Cyl | Exact CID | Litres |
|---|---|---|---|---|---|
| Chevy 283 | 3.875 | 3.00 | 8 | 283.0 | 4.64 |
| Chevy 302 (DZ) | 4.000 | 3.00 | 8 | 301.6 | 4.94 |
| Chevy 327 | 4.000 | 3.25 | 8 | 326.7 | 5.35 |
| Chevy 350 | 4.000 | 3.48 | 8 | 349.8 | 5.73 |
| Chevy 383 stroker | 4.030 | 3.75 | 8 | 382.7 | 6.27 |
| Chevy 400 | 4.125 | 3.75 | 8 | 400.9 | 6.57 |
| Chevy 427 (BBC) | 4.250 | 3.76 | 8 | 426.7 | 6.99 |
| Chevy 454 (BBC) | 4.250 | 4.00 | 8 | 454.0 | 7.44 |
| Ford 289 | 4.000 | 2.87 | 8 | 288.5 | 4.73 |
| Ford 302 | 4.000 | 3.00 | 8 | 301.6 | 4.94 |
| Ford 351W | 4.000 | 3.50 | 8 | 351.9 | 5.77 |
| Ford 460 | 4.360 | 3.85 | 8 | 459.8 | 7.54 |
| Mopar 340 | 4.040 | 3.31 | 8 | 339.4 | 5.56 |
| Mopar 360 | 4.000 | 3.58 | 8 | 359.9 | 5.90 |
| Mopar 440 | 4.320 | 3.75 | 8 | 439.7 | 7.21 |
A genuine 350 is 349.85 CID from 4.00 × 3.48. If your bore mikes at 4.030 or the stroke is 3.75, you are not holding a stock 350 — you are holding something that has been machined, quite possibly the classic 383 stroker.
The LS family, by exact geometry
LS engines complicate the picture because the factory badges litres while enthusiasts talk cubic inches. The panel shows both; here is the family laid out:
| LS engine | Bore in | Stroke in | Exact CID | Litres | Marketed |
|---|---|---|---|---|---|
| LS1 / LS6 | 3.898 | 3.622 | 345.8 | 5.67 | 5.7 L |
| LS2 | 4.000 | 3.622 | 364.1 | 5.97 | 6.0 L |
| LS3 / L99 | 4.065 | 3.622 | 376.1 | 6.16 | 6.2 L |
| LS7 | 4.125 | 4.000 | 427.6 | 7.01 | 7.0 L |
| LSA / LS9 | 4.065 | 3.622 | 376.1 | 6.16 | 6.2 L (blown) |
| LQ4 / LQ9 | 4.000 | 3.622 | 364.1 | 5.97 | 6.0 L truck |
LS1, LS6 and LS2 share a 3.622-inch stroke and separate on bore; the LS7 jumps to a 4.125-inch bore and a 4.00-inch stroke for its 7.0 litres. Load the closest preset and edit it to match your actual measurements.
Building a 383 from a 350
The most famous small-block build is a 350 block bored 0.030 over to 4.030 inch and fitted with a 3.75-inch stroke crank. Enter those and the calculator returns about 382.67 CID — the "383". It is worth seeing where the gain comes from: the overbore alone adds only about 5 cubic inches, while the stroker crank does the rest. Stroke is the lever; the bore is the fine adjustment.
Nominal or measured?
For a stock, unopened engine, the preset's nominal bore is fine. For anything with miles or machine work, measure — a cleaned-up 4.030-inch bore is a few cubic inches larger than 4.00, and on a build that can matter for class rules or just for honest advertising. Switch the panel to Build precision to see the decimals a machinist works to.
Big-block is a different animal
A 454 is not a stretched small-block; it is a big-block architecture with a 4.25-inch bore and a 4.00-inch stroke for 453.96 CID. If someone offers you a "454" measuring 4.00-inch bore, walk away — the bore alone tells you it is a small-block wearing the wrong name.
References & standards
- SAE J1349 — Engine power test code — the standard behind 'SAE net' crankshaft ratings.
Frequently asked questions
Is a Chevy 350 really 350 cubic inches?
Not exactly — it is 349.85 CID from a 4.00 in bore and 3.48 in stroke. The '350' is a rounded badge, and the preset here shows the precise geometry.
What are the LS1 bore and stroke?
3.898 in bore and 3.622 in stroke across eight cylinders, giving about 345.8 CID or 5.67 L — often marketed as a 5.7.
How do I calculate an LS3's displacement?
Use its 4.065 in bore and 3.622 in stroke; eight cylinders give about 376 CID or 6.16 L. The LS3 preset loads those numbers for you.
What makes a 383 stroker?
A 350 small-block bored 0.030 over to 4.030 in and fitted with a 3.75 in stroke crank, giving about 382.67 CID — the classic budget stroker.
How is a big-block 454 different?
It uses a much larger 4.25 in bore and 4.00 in stroke, giving about 453.96 CID (7.4 L) — a big-block architecture, not a stretched small-block.
Can I tell an LS apart by bore and stroke?
Often yes. LS1/LS6 and LS2 share a 3.622 in stroke but differ in bore; the LS7 jumps to a 4.125 in bore and 4.00 in stroke for 7.0 L. The preset chart lists them.
The seller says it's a 350 — how do I verify?
Measure the bore and stroke and calculate. A true 350 lands at 349.85 CID; a 4.030 in bore or a longer stroke means it has been bored, stroked or is a different block.
What is an LQ4 or LQ9?
6.0 L truck LS engines with a 4.00 in bore and 3.622 in stroke — a common, strong basis for builds. Enter those figures for their exact displacement.
How much does a 0.030 overbore add to a 350?
About 5.3 CID, roughly 1.5%, taking 349.85 to around 355 — small next to what a stroker crank adds, which is why stroking is the popular route.
Do I use nominal or measured bore for an LS?
Measured, if it has been machined or has miles on it. A stock LS1 is 3.898 in, but a cleaned-up bore is slightly larger and shifts the displacement.
Can I build a custom small-block figure here?
Yes. Load a preset as a starting point, then edit bore, stroke or cylinder count to model your exact combination and read the new CID and litres.
Why do LS engines list litres and CID both?
Because they straddle two markets — enthusiasts talk cubic inches while the factory badges litres. The panel shows both so a 6.2 L reads across to about 376 CID.
What bore and stroke give a 6.0 L LS?
A 4.00 in bore with a 3.622 in stroke lands at about 364 CID, or 6.0 L — the LS2 and truck-LS figure.
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