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"Make 4WD Mechanix Magazine and the 'Tech and Travel' Forums your online resource for Jeep, 4x4 truck, powersports and dual-sport motorcycle maintenance, troubleshooting, repairs, rebuilding, engine tuning, upgrades, backcountry trail prep and overland travel tips!"Moses Ludel, Publisher

HD Vlog: Performance Testing a 4.6L Jeep Inline Six Stroker Motor!

Hosted by Moses Ludel 

The Jeep inline six stroker motor has been a popular topic! In this HD vlog, hear Moses Ludel describe a Hewes Performance Machine engine that now powers a 1998 Jeep XJ Cherokee. Hear Moses' comments on this engine build and how the Jeep performs! (See the build components list below. Also see the 6-part HD video interview series with Tony Hewes, available exclusively at the 4WD Mechanix Video Network!) 

     There are many configurations for the Jeep inline six stroker motor. At a 0.030" (typical cleanup) rebore with the 4.2L/258 crankshaft, the new displacement is 4.6L. (A stock 4.0L bore with a 258 crankshaft equals 4.5L; a 0.060" rebore with 258 crankshaft equals a 4.7L displacement for this engine buildup.) With the special attention to the cylinder head porting, exhaust upgrades, balancing and use of the 24-pound Ford 5.0L V-8 injectors (Ford part #F1TE-D5A or Bosch 280 150 947), this engine should dyne around 260 horsepower with the 8.7:1 compression ratio and CompCams 252 grind camshaft.

     Note and Caution on late coil-pack ignition engines—The injectors described above are for a pre-coil pack 4.0L engine application. Coil pack engines typically require 24-pound injectors like the 2000-2003 5.9L Dodge Ram V-8 square-plug type. These are available as rebuilt types (GB812-12132) from HESCO and others...Also, the CompCams' 252H grind is discussed in the videos and listed in the parts below...This camshaft has performed and tested well in pre-coil pack 4.0L stroker builds. We are currently considering whether or not this is the optimal camshaft for 1999-up TJ Wrangler and 2000-up XJ Cherokee builds with the late coil-pack ignition and cylinder head redesign. Stay tuned for our findings about camshaft grinds and tune for the later coil pack engines...The engine parts listed below are for a 1998 Jeep XJ Cherokee with pre-coil pack ignition and cylinder head, using a factory PCM.

  For Jeep use, the real success story with the 4.6L stroker six is the torque output and torque curve. Torque rises far more quickly than a stock 4.0L and should exceed peak 4.0L torque by at least 50 ft-lbs! Most of the torque comes in by 2,000 rpm, and this improves the real world driving feel and trail crawl performance. Torque continues to climb to a peak in the 300-340 ft-lbs range by 3,200 rpm—depending upon the build. On the engine tested, the moderate compression ratio and camshaft, balancing, head porting and exceptional parts quality make this a "longevity" engine, clearly built for 250,000 miles of troublefree Jeep 4WD service!

5.0L Ford V-8 injectors for the stroker Jeep inline six HESCO water pump and thermostat housing

At left is the stock 4.0L Jeep multi-point port injector rail with 5.0L Ford replacement injectors fitted neatly in place of OEM injectors. This modification meets potential fuel demands of a 4.6L stroker—without adversely affecting drivability or tailpipe emissions! At right is a HESCO thermostat housing and water pump to enhance flow with the Griffin radiator.

Griffin high performance radiators for Jeep XJ Cherokee Forged pistons for Jeep inline six stroker motor

At left are two Griffin performance radiators for the XJ Cherokee, each capable of handling high horsepower output from a 4.6L stroker six. The thicker core unit is now in the '98 XJ Cherokee described at this vlog. (Left unit resides in the magazine's 1999 XJ Cherokee with its current 4.0L OE engine. See Griffin radiator installation how-to.) At right, rods and pistons for a stroker six are available in cast hypereutectic or forged design.

     Key Parts and Machining for This Stroker 4.6L Inline Six:

Key Engine Parts (beginning with the stock 1998 Jeep XJ Cherokee block assembly and cylinder head casting) 

Cam bearings: Sealed Power

Rods: Stock 4.0L from 1998 XJ engine core

Camshaft: CompCams 252 grind with lifter (flat tappet) kit

Crankshaft:  Stock 4.2L/258 core, fully machined and balanced (snout length machined for serpentine pulley)

Hard exhaust valve (replacement) seats and high performance valves

Full gasket set

Brass freeze plugs

Harmonic balancer: stock, balanced with other reciprocating parts

Main bearings: King 0.010” undersize for machined crankshaft

Rod bearings: King 0.010” undersize for machined crankshaft

Oil pump: Melling high volume with new pickup screen

Pistons: Forged IC944 0.030” oversize with pins

Piston rings: Hastings 667 in 0.030” oversize

Timing chain set: Cloyes performance

ARP rod bolts for 4.0L connecting rods

Silicone bronze valve guide liners

CompCams new valve springs


Key Machining Operations

Hot tank block, head and reusable parts

Align hone main bearing saddles with main caps

Deck block for straightness and establishing correct piston crown height

Bore and hone to 0.030” oversize finish

Regrind 4.2L/258 crankshaft core

Balance all reciprocating engine parts

Fit pistons and pins to rods

Fit new “hard” exhaust valve seats

Machine and fit silicone bronze valve guides

Magnaflux all castings

Align and hone stock Jeep 4.0L rods

R&R cam bearings

Surface cylinder head

Set valve stem heights (for correct lifter plunger heights)

Complete “valve job” with machined valve seats, intake valves and spring seats

Four hours of cylinder head porting and header port match

Assemble long block to proper tolerances and fit


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