Overbore & Stroker Displacement Change
Before-and-after displacement for an overbore, a stroker crank, or both at once.
| Before | 349.85 | cu in |
| Before | 5.733 | L |
| After | 382.67 | cu in |
| After | 6.271 | L |
| Change | 32.82 | cu in |
| Change | 537.8 | cc |
| Change | 9.38 | % |
- V = (π ÷ 4) × bore² × stroke × cylinders, computed before and after
- change % = (after − before) ÷ before × 100
When you need it
When deciding whether a machining operation or a stroker kit is worth the money.
What it usually shows
A .030 inch overbore on a small block adds roughly one and a half percent — about five cubic inches on a 350. That is inside the noise on a dyno.
Overboring is how you clean up worn, scored or corroded cylinders and get back to a round, straight hole. It is a repair operation. The displacement it adds is a side effect, not a reason.
Stroke is where the displacement lives
Going from 3.48 to 3.75 inches of stroke on the same bore is close to ten percent, and you feel it everywhere in the torque curve.
It is not free. More stroke raises mean piston speed at any given RPM, lowers the rod ratio unless you change rods, and usually needs clearancing at the block and a different piston compression height. A stroker is a rotating assembly decision, not just a displacement one.