Putting a Cubic-Inch Engine Number Into Litres
American engines were sold by the cubic inch for decades, and the number stuck: it is cast into blocks, stamped on valve covers, painted on air cleaners and typed into classified ads. Almost everywhere outside a swap meet, though, the same engine is described in litres. If you are looking at a 350, a 427 or a 454 and everyone around you is talking about 5.7, 7.0 and 7.4, one multiplication closes the gap.
Why the Two Numbers Sit Side by Side
Displacement figures that became nicknames
Machine work moves the number
Forms ask in litres, owners answer in cid
Rounding is generous
From Casting Number to Litre Figure
Whether the cubic-inch number came off a block, a build sheet or a for-sale listing, the sequence is the same.
Enter the cubic-inch figure
Type 350, 427, 454 or the exact displacement your machinist calculated into the left field. The litre value appears as you type — no button to press, and a comma works instead of a dot if that is how you write decimals.
Decide how far to round
Results carry up to eight decimals, so you can see 5.735472 L in full. Badges and club rules use one decimal; a technical inspection sheet may want two. Round it yourself, once, at the end.
Copy the plain number onto the form
The copy button hands over the bare figure with no unit attached, which is exactly what a registration field or a spreadsheet cell wants. Ctrl + C inside a field does the same thing.
Go the other way from a badge
Seen a "6.2 L" and want to know what that is in the old money? Press the swap button (↔) to run L → in³. By hand, multiply litres by 61.0237441: 6.2 L is about 378 cubic inches.
Iconic American V8 Displacements
The engines whose cubic-inch names are still in daily use, with the arithmetic done in full and the litre figure the market actually quotes.
| Engine | Displacement (in³) | Exact volume (L) | Litre figure quoted |
|---|---|---|---|
| Ford small block "302" | 302 in³ | 4.948893 L | 5.0 L |
| Chevrolet small block "350" | 350 in³ | 5.735472 L | 5.7 L |
| 383 stroker small block | 383 in³ | 6.276246 L | 6.3 L |
| Chevrolet big block "396" | 396 in³ | 6.489277 L | 6.5 L |
| Big block "427" | 427 in³ | 6.997276 L | 7.0 L |
| Big block "454" | 454 in³ | 7.439727 L | 7.4 L |
Notice how neatly 427 lands on 7.0, and how far 302 has to travel to reach its 5.0 badge. That gap is the whole reason to keep the exact figure somewhere: two engines separated by fifteen cubic inches can end up wearing the same number on the fender.
What Helps When You Are Working From a Block
Type the cid, read the litres
Both boxes stay live, so you can run through a whole family of blocks — 265, 283, 302, 327, 350 — without clearing anything between entries.
Badge-to-block check in one press
The swap button reverses the direction when a listing gives you litres and you want to work out which casting is likely to be under the hood.
Pick any volume unit on either side
Searchable dropdowns list every volume unit, so an odd displacement can be read out in millilitres or cubic centimetres when a form insists on those.
Figures clean enough to paste
Up to eight decimals on screen and a copy button that strips the unit, so nothing extra ends up in a form field or a build spreadsheet.
Engine Displacement Questions
Why is a 350 cubic-inch engine sold as a "5.7 L"?
Because 350 in³ is 5.735472 L, and a badge only carries one decimal place. When American manufacturers moved to metric naming, the same casting simply picked up a metric label — nothing inside the engine changed. The 5.7 L on a Corvette or a truck tailgate is the 350 you already know.
How do bore, stroke and cylinder count give the displacement?
Displacement is the swept volume of one cylinder multiplied by the number of cylinders: π/4 × bore² × stroke × cylinders, with bore and stroke in inches. A classic small block with a 4.000 in bore and a 3.480 in stroke gives 0.7854 × 16 × 3.48 × 8 ≈ 349.8 in³ — the 350. Feed that answer straight in and it comes back as 5.73 L.
Why do two different cubic-inch figures wear the same litre badge?
Rounding swallows the difference. A 302 is 4.948893 L and a 305 is 4.998055 L — both round to 5.0. A 346 comes out at 5.669924 L and a 350 at 5.735472 L, and both are called 5.7. One decimal place covers a wide span of cubic inches, so the badge alone never identifies the engine.
My block has been bored and stroked — what displacement should I quote?
Recalculate from the finished dimensions, not the original badge. Use the measured bore after machining and the stroke of the crank actually installed, run the swept-volume formula, then convert. A 350 taken 0.030 in over and given a 3.750 in stroke arrives at roughly 383 in³, which is 6.276246 L — that is the number for a tech card, not 5.7.
What figure goes on an import registration or an insurance form?
Almost every such form asks for engine capacity in litres or cubic centimetres, usually to one or two decimals, and often ties a tax or premium band to it. Convert the true displacement, round the way the form asks, and keep the working: a 454 is 7.439727 L, so 7.4 L or 7440 cc depending on the box you are filling in. Quoting a rounded badge for a modified engine can land you in the wrong band.
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