The Worcestershire paceman took two wickets with the new ball as their opponents chased a 215 target.
Finch, 17, helped to reduce the South West to 37-5 with figures of 6-1-20-2 before they were skittled for 125.
Opener Jack Haynes scored six, County team-mate Zain Ul-Hassan eight and Finch two.
ADAM Finch played his part as Midlands under 17s defeated the South West by 89 runs in the Super Fours opener at Loughborough.
In the series against India, who won 5-0, he had figures of 1-36 at Cardiff and 0-21 at Taunton.
They have warm-up matches against Ireland in Christchurch and Sri Lanka in Lincoln.