My 4.X liter Jeep Stroker Recipe
By Corey Kruchkowski
Note 1: All part numbers current as of May 2009.
Note 2: Where not mentioned, standard engine rebuilding
techniques apply.
Note 3: This is a tested recipe. Fieldtested,
and comp tested.
The
Block:
‐ To avoid unnecessary frustration, run the block from the
generation of engine that came in the vehicle that you are
placing the motor into. There were 4 versions/generations of
the 4.0L block and all had minor EXTERNAL variations. Read
the casting under the exhaust headers.
‐ If you are running a competition buggy, run a highmileage
Renix 4.0L engine (casting dates up to 1990, Gen 1 cast on
drivers side). It has higher nickel content and will be well
seasoned. It is the toughest block from a metallurgical
standpoint, and highly recommended for competition.
‐ Bore 0.040 over if possible. The engine will run cooler, and
one more rebuild (0.060) will remain if the unforeseen
occurs.
‐ Have new cam bearings installed.
‐ Install bottomend
studs in the block. Hesco part number
HESMS6 Hesco ARP Bottom End Studs. Install as per
Hesco/ARP instructions.
3
‐ Install head studs in the block. Hesco part number HESHS6
Hesco ARP Top End Studs. Install as per Hesco/ARP
instructions.
The Crank:
‐ The best 258 (4.2L) crank to run is the 198790,
3727 4
counterweight crank. It weighs 46lbs, and has a 54mm snout.
This crank is a direct bolt in to the 4.0L block and works with
a stock 4.0L harmonic dampener.
‐ If 3727 cranks are unavailable or difficult to find, the second
best 258 (4.2L) crank to run is the 198186,
3235477 4
counterweight crank. It weighs 46lbs, but has a 64mm snout.
This crank needs a 10mm spacer or 10mm removed from the
snout to work with a stock 4.0L harmonic dampener.
‐ Under no circumstances should a 12counterweight
crank be
used to build a Jeep inline Stroker engine.
‐ Have the crank spinbalanced.
Generally this only takes a
competent shop 1/2hr – 1hr, as they are very close from the
factory. Have all the oil holes chamfered. Check the pilotbearing
journal if you are running a standard trans,
machine/enlarge as necessary.
The Rods:
‐ You must run the longer 4.0L rods. This is both a power and
longevity issue. Yes – it requires custom pistons.
‐ Deburr all the casting flashes off the sides of the 4.0L rods.
Blastpeen
the rods in a highpower
bead blast cabinet to
surface harden. Resize. Install ARP stud kit PN 1126001.
Install as per ARP instructions.
‐ The casting number for all the years of the 4.0L rod is
53020126.
4
‐ Weight balance the rods before pressing them into the
pistons, then weight balance each rod and piston assembly
endforend.
The Pistons:
‐ Now that Keith Black has added 4.x liter Stroker pistons to its
catalog, these are the ONLY pistons to run in a normally
aspirated 4.x liter Stroker engine. Installing these pistons on
a 4.0L rod will result in a deck clearance of 0.028, on a block
that has not been decked. Two varieties have been created.
‐ KB Silvolite forged 944 come with a 21.7cc dish, resulting in a
9.5:1 compression ratio. This is the piston recommended for
stock 4.0L fuel systems (minus larger injectors of course) and
the milder 4.0L camshafts.
‐ KB Silvolite forged 945 come with an 11.4cc dish, resulting in
a 10.5:1 compression ratio. This is the piston recommended
for modified 4.0L fuel systems, and the most aggressive cam
profiles.
‐ A little known fact is that Chevy 283 rings work in Jeep 4.0L
engines. Run PlasmaMoly
racing rings for easy breakin
and
toughness. I like Hastings products, the quality is control is
excellent: PN 2M5506(
0.20304060).
File to fit for a
perfect match.
The Head:
‐ If the correct head is chosen, no modification is necessary to
the intake and exhaust runners.
‐ There are 4 head castings for the 4.0L head.
‐ The HO, or HiPo heads were in existence between 1991 and
1998. Casting numbers 7120 and 0630. The 7120 heads have
the coolant gauge sender necessary for ODB1 systems. These
5
two castings are the only ones worth considering for an
engine build.
‐ A 5angle
valve job is necessary.
‐ Stock valves may be reused
in all but the most extreme
applications.
‐ To run the camshafts I recommend, use MOPAR PN 5249464
springs with MOPAR 4452032 retainers. This combo is good
for cams with over 0.0500” of lift.
The Camshaft:
‐ I only recommend three cams for the 4.0L Stroker. Crane is
no longer in business, and one company in particular
continues to provide the best cams for this engine. I have
tried Isky, Clifford, Hesco and others – but came back to
Comp. Still the best profiles for this engine.
‐ For each cam, use Comp antipump
up lifters. PN 82212
‐ Stock replacement 4.0L pushrods are acceptable in normally
aspirated applications.
‐ For the best bottommid
trail crawling/tractor engine, use
Comp Cams PN 682324.
‐ For a midupper
screamer competition engine, use Comp
Cams PN 682394.
This cam will work best with compression
ratios of 9.5:1 and higher.
‐ For a great allaround
engine with mild street manners,
choose Comp Cams PN 682314.
Extras:
‐ Choose a double roller chain for durability, and reliability
during competition/racing and decreased friction. These
6
chains are manufactured and sold by Cloyes PN 93127,
and
supplied by MOPAR P5249519, and Comp Cams COC3127.
The chains work in all the 4.0L engines – a minor DIY
modification is required to the way the cam shaft is retained
in 99 and newer blocks (it is quite obvious once assembly is
undertaken).
‐ Run Harland Sharp pedestal mount rollerrockers
– they bolt
in with no modifications required. You must always check for
head & valve cover clearance and proper lifter preload. PN
S40196
FINAL WORDS:
• The above combo is the best balance of power and budget in
my opinion, when building a Jeep Stroker motor.
• If done properly, and attention to detail is maintained
throughout machining and assembly, 300+ horsepower and
350+ ft/lbs torque is expected with the 9.5:1 pistons. I am
unsure on the numbers for the 10.5:1 pistons (more) – but
fuel upgrades above and beyond oversized injectors must be
performed. Contact me for details on your specific
applications.
• Please let me know what you think, I welcome your input. If
you use this combo to compete – please give me credit for
your engine specs.
Best Regards,
Corey Kruchkowski
[email protected]
mobile (780) 9334012
http://tntgp.com
