Larger Injectors for Stroker
Stock 19 lb/hr. Strokers need 24 lb/hr (Mopar 5.9 'yellow tops'). High-output strokers and supercharged setups need 30+.
Injector sizing scales with peak power demand. Approximate rule: HP / (cylinders * BSFC / 60 * duty cycle). For a 250 hp 4.6 stroker at 0.50 BSFC and 85% duty: ~22 lb/hr per cylinder. Stock 19 lb/hr maxes out around 215 hp.
Common upgrade paths:
- 21 lb/hr (Bosch 0280155710): stock HO size, cheap refresh
- 24 lb/hr Mopar 'yellow tops' from 5.9 Magnum truck (PN 53030343 or 5037479AA): direct drop-in, perfect impedance match, the canonical stroker injector. Used set $80, new set $200-280.
- 30 lb/hr (Bosch III): for high-output strokers, supercharged, or turbo. Requires PCM tune adjustment (injector slope) or it'll run rich and pig-rich at idle.
The injector slope (lb/hr value the PCM uses to calculate fuel quantity from pulse width) lives in the PCM tune. With a stock 19 lb/hr slope and a physical 24 lb/hr injector, the engine runs ~25% rich. You need either a custom tune (HPTuners on 96+ trucks) or to find a PCM that already has 24 lb/hr slope (some 5.9 Magnum PCMs). Many stroker builders accept slightly off fuel trims and let the closed-loop O2 correction handle it, which works at cruise but not WOT.
If you can do only one fuel mod for a stroker, do the 24 lb/hr injectors. Pair with the Walbro 255 pump for headroom.
Why it works
- meaningful for stroker
- drop-in physically
Trade-offs
- tune adjustment needed
- WOT mixture off without tune
Tools required
- socket set
- fuel line disconnect tool
Parts
| Part | Vendor | Est. price |
|---|---|---|
| Mopar 24 lb/hr yellow top injectors (set 6) | Mopar | ~$240 |
| Bosch III 30 lb/hr injectors (set 6) | Bosch | ~$360 |
| Fuel injector o-ring kit | FelPro | ~$20 |
Sources
Related
- Fuel Pump Upgrade (Walbro 255 for Stroker)
- All Jeep Cherokee XJ guides & tools
- Browse the full DIY database
Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.