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Plymouth Chrysler 2.5 TBI balance-shaft specs: 153 ci (2.5L) 4-cylinder, 3.445 x 4.095 in (87.5 x 104 mm) bore and stroke, 9:1 compression. Rated 100 hp.
The Plymouth Chrysler 2.5 TBI balance-shaft is undersquare — the 4.0945" stroke exceeds the 3.4449" bore by 15.9% — a layout that trades peak RPM for leverage and torque low in the range. The 4.0945" stroke puts mean piston speed at 4,000 ft/min around 5,850 RPM, which is where a production bottom end is generally considered at its limit. Each of the 4 cylinders displaces 38.3 ci (627 cc).
9:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.
It is one of 5 engines in the K-Engine family, the largest at 153 ci. 4 factory variants share these dimensions, rated at 100 hp across 1986–1989.
| Displacement | 153 ci / 2.5 L |
|---|---|
| Bore | 3.4449" |
| Stroke | 4.0945" |
| Cylinders | 4 |
| Configuration | I4 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 0.841 |
| Block material | cast iron |
|---|---|
| Head material | aluminum |
| Valvetrain | SOHC |
| Fuel type | gas |
| Advertised HP | 100 hp |
| Years | 1986–1989 |
| Year | Version | HP @ rpm | Torque @ rpm | Comp. |
|---|---|---|---|---|
| 1986 | net | 100 @ 4800 | 136 lb-ft @ 2800 | 9:1 |
| 1987 | net | 100 @ 4800 | 136 lb-ft @ 2800 | 9:1 |
| 1989 | net | 100 @ 4800 | 135 lb-ft @ 2800 | — |
Factory specification sheet.
| Bore/stroke character | 0.841 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 4,095 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 38.3 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1986 | 100 hp | Chrysler 2.5 TBI balance-shaft |
| 1987 | 100 hp | Chrysler 2.5 TBI balance-shaft |
| 1988 | — | Chrysler 2.5 TBI balance-shaft |
| 1989 | 100 hp | Chrysler 2.5 TBI balance-shaft |
1 factory vehicle, 1986–1989. Each year opens that model's engine table.