AMC 258 crankshaft (3.895" stroke) in a 4.0L block with .030 over pistons. Yields ~4.6L (281ci) and ~245-275 hp / 290-320 lb-ft with cam and head work.
The 4.6 stroker is the canonical XJ engine build. You start with a healthy 4.0L block (87+ for the better main webs), bore .030 over to 3.905", and install a 3.895" stroke AMC 258 crankshaft. Connecting rods are either reconditioned 258 rods (cheap, adequate) or 4340 forged rods (Eagle, Scat — for higher RPM or boost). Pistons are Hesco, KB, or Diamond hypereutectic/forged with the wrist pin moved up to compensate for the longer stroke.
Typical recipe (Hesco / Dino Savva / 'standard 4.6'):
Dyno results vary widely — a clean 4.6 with the above will typically make 245-265 whp and 290-310 lb-ft on a Mustang dyno. Builders chasing the high end with bigger cam and head work see 280+ whp.
Cost: $4000-7000 in parts and machine work for a DIY build, $7000-10000 turnkey from a builder like Hesco or Golen.
Reliability: a properly built stroker outlasts the stock motor. Hesco short blocks have 200k+ examples on the road. Do not skip balancing — the 258 crank in a 4.0 block must be balanced as an assembly.
| Part | Vendor | Est. price |
|---|---|---|
| Hesco short block 4.6 | Hesco | ~$4200 |
| Comp Cams 68-232-4 cam/lifter kit | Comp Cams | ~$360 |
| Mopar 24 lb/hr injectors | Mopar | ~$240 |
| Walbro 255 fuel pump | Walbro | ~$110 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.