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Details Needed for 4.6L Stroker Build-up on 2000-2006 Jeep Wrangler


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My dilemma, I have a 2005 Jeep Wrangler Rubicon LJ that unfortunately fell victim to the dreaded OPDA failure at 79K. Since I already have to replace the camshaft I figured now would be the best time to build a Stroker. I've read a lot about people doing them with '99 and older jeeps but can't seem to find any real good info on building a 4.6 out of a '05-'06 wrangler. I currently have my block and head completely stripped down and ready for the machine shop. Along with a 4.2 crank ready for the swap. I also have both the 4.2 and 4.0 rods to choose from.

Problem #1: 4.6l pistons .030

I'm looking for the best piston to achieve an 87 octane stump puller. I'm looking for one that will give me the correct quench without machining the block if necessary, being my block is in perfect shape. Along with the correct dish to achieve the compression I'm looking for. Whether that's a forged or cast piston.

Problem #2: camshaft.

I can't find a camshaft that will work for this application for an '05. I was looking at the comp cams 68-232-4 but not sure if this set up will work with the '05 head?

Thanks for any advice you can give.

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Hi, O5LJspider...Welcome to the forums!  From our Tony Hewes interviews and other details at the magazine, you are aware of the 0.010" block deck issue when using the 4.2L crankshaft with the wrong connecting rods and pistons.  For details on piston designs used over the years in Jeep 4.0L and 4.2L inline sixes, see the Silv-O-Lite piston catalog:  https://www.uempistons.com/catalogs/silvolite_catalog.pdf.  Look up AMC/Jeep engines and these sixes.  Dimensions are provided there.  The catalog listings go through 2002.  I explored the Mopar 4.0L piston part numbers for 2002 and your 2005, they are the same for stock pistons.  Note that these pistons are "fitted" OEM standard bore size items:
 
2002
04798329AC 6 ER0 B Size 3.8742
04798330AC 6 ER0 C Size 3.8746
04798331AC 6 ER0 D Size 3.8750
04798332AC 6 ER0 E Size 3.8754
04798333AC 6 ER0 F Size 3.8758
 
2005
04798329AC 6 ER0 B Size, 3.872
04798330AC 6 ER0 C Size, 3.8746
04798331AC 6 ER0 D Size, 3.8750
04798332AC 6 ER0 E Size, 3.8754
04798333AC 6 ER0 F Size, 3.8758
 
I took this back to 1999, a common distributor era block and head for stroker builds and used in my own stock 4.0L XJ Cherokee engine.  The piston numbers are different:
 
04798329 6 ER0 B Size, 3.8742
04798330 6 ER0 C Size, 3.8746
04798331 6 ER0 D Size, 3.8750
04798332 6 ER0 E Size, 3.8754
04798333 6 ER0 F Size, 3.8758
 
I took these OE numbers and checked for current Mopar superceded numbers. Your 2005 OE Mopar replacement piston (using "D" sizing as an example) is interchangeable with the 1999 04798331 piston and other 4.0L applications: 04798331AC ; 04798331; 04798331AB; 53020508; 53020508AB. What this says is that the Silv-O-Lite pistons to 2002 should also work in your engine. I recommend that you confirm this with United Engine. Also ask United Engine which rods they recommend for your stroker build, the 4.2L or 4.0L rods, and the block deck height requirements.  United Engine offers Icon, Silv-O-Lite and KB pistons.

 

You may find that it is simpler and cost effective to deck the block to match recommended piston height.  Follow up by confirming the valve lifter clearance (see my vlog discussion on valve clearances and adjustment at the magazine home page) and in the Hewes interviews.  Decking is considered a "normal" remanufacturing process and often corrects for factory imperfections and also the distortion or "seasoning" impact of engine heat over time.  Your engine and head design runs plenty hot, and these castings are likely not that "perfect".  Decking is a practical part of any quality engine rebuild.  If you're boring and honing the block 0.030", this is one more reason to consider block decking. 
 
There are two factory 8.8:1 compression pistons offered by Silv-O-Lite.  These are cast hypereutectic type pistons that I've used trouble-free for decades in a range of engine builds.  I agree with your call that forged pistons would be overkill for a lower compression "stump puller" run to 4500-5000 rpm maximum under normal conditions.  Here are the Silv-O-Lite 8.8:1 offerings, note that the piston rings are either metric or U.S. sized with different groove depth.  The 0.116" depth dish is desirable for your lower compression ratio goal...You'll find this information and more in the Silv-O-Lite catalog:
 
L6-242
4.0L
3.8750(IN)
98.4(MM)
AMC
ENGINE
1996-02
8.8
S Hypereutectic. “D” shaped head recess
.116” deep. “COATED SKIRTS”.
Not intended for Racing applications.
COMP HT: 1.592 PIN DIA: .9310 Offset
3241HC
STD.
.020
.030
.040
.060
2-1.5mm
1-4.0mm
Shallow
Groove
04798331
FM H802CP
L6-242
4.0L
3.8750(IN)
98.4(MM)
AMC
ENGINE
1996-02
8.8
Hypereutectic. “D” shaped head recess
.116” deep. “COATED SKIRTS”.
Not intended for Racing applications.
Same as 3241HC with early ring pack
COMP HT: 1.592 PIN DIA: .9310 Offset
3242HC
STD.
.020
.030
.040
.060
2-5/64
1-3/16
FM H825CP
 
Let us know what you turn up with United Engine.  They are knowledgeable about AMC/Jeep engine applications and the Jeep stroker needs.  If the longer stroke pushes compression higher than you want, use a thicker aftermarket head gasket like the Felpro (blue coated) design.  A thicker head gasket can drop compression slightly.  A countersunk piston (not reaching block deck height) will also do this, but you will loose the optimal quench that you desire.
 
As for camshaft choices, your late 4.0L tuning does require a different grind than the 252 CompCams that we traditionally recommend for stump pulling Jeep inline sixes.  The time-honored 252 grind works well to 1999 distributor type engines; however, coil-on-plug engines have distinctly different camshaft centerline requirements with the camshaft position sensor's demands.  Here is my discussion of the recommended grind (custom, though earmarked to enter the CompCams catalog under a part number) from Daniel Prate at Tech Support:
 
Daniel Prate, CompCams Tech Support:  Moses, We have a custom grind that our customers have been very pleased with.  It has a duration @ 0.050" of 206/212, with valve lift being .435/.448, and a lobe separation angle of 113° (110-degree intake centerline).  The cam price is $186.15.
 
Moses: Do you recommend this cam for the stock 4.0L (late coil-on-plug inline six) engine and also the 4.6L stroker build on that platform?  Does the cam perform like the traditional 252 grind, targeting low-end and mid-range power with good idle/lower speed manifold vacuum?  Will you be making a catalog listing for this cam?  How do the magazine’s reader/viewers access this camshaft?  Is there a reference number or camshaft card number?
 
Moses, I do recommend that cam for the stock 4.0L as well as the 4.6L.  It performs like the 252 grind, and we do not have any information about whether or not this cam will become a catalog cam.  You can order this camshaft directly through me, or any of us here in the tech office.
 
Here is Daniel Prate's contact information.  You can discuss this camshaft with anyone at CompCams Tech Support:

 

Daniel Prate

Technical Sales & Support

 

COMP Performance Group™

3406 Democrat Rd.

Memphis, TN  38118

 

Toll Free: (800) 365-9145 ext. 1516

Fax: (901)366-1807    

dprate@compcams.com

www.compperformancegroup.com

 

The final consideration is injector sizing.  Some builders use the 5.0L Ford 302 24#/hr. type, and there are even references to GM LS1 25.2#/hr. injectors for later '05/'06 engines.  A website with a penchant for Jeep inline stroker motors shares this build formula for a lower compression ratio "rock crawler" like you or I would want.  Here is a recommended build courtesy of the http://www.jeep4.0performance.4mg.com/stroker.html website.  There is other information at that site on connecting rod choices and build details.  The Mopar/Victor 0.043" head gasket and quench adjustments get considerable mention.  See that site for more examples:

 

4.6L Low-buck, low CR "rockcrawler"

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom forged +0.030" bore pistons, compression height 1.380", dish volume 32cc
8.8:1 CR
CompCams 68-115-4 192/200 degree camshaft
DIY ported HO 1.91"/1.50" 57cc cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Ford 24lb/hr injectors for '87-'95 engines, Accel 24lb/hr injectors for '96-'04 engines, '98 Chevy LS1 25.2lb/hr injectors for '05-'06 engines
242hp @ 4600rpm, 317lbft @ 3000rpm"

 

What to note from this particular build: Custom forged pistons used; 4.0L rods; dish volume of 32cc; 0.043" head gasket; injector comments.  The output is likely accurate for the camshaft and tune.  This engine has reasonable horsepower and substantial torque gain.  The torque peak rpm is higher than I like, this could be remedied with PCM tuning like my Max Energy tune in the XJ.  Camshaft choice plays a role here, too.

 

For additional access to tuning information, go to my lengthy index of 4.6L information at this forum topic:  http://forums.4wdmechanix.com/topic/493-which-camshaft-for-a-2000-jeep-xj-cherokee-stroker-46l-engine-build/?hl=compcams#entry2747.  See the list of tuning articles and other details.

 

Our 1999 4.0L engine now has 157,000 miles on it.  At some point, it will be due for a rebuild.  When that time comes, the stroker build will likely become a Vimeo-On-Demand how-to rental video like I've done with other Jeep, Dodge Ram and Honda XR motorcycle topics.  With sublet machining to a shop like Tony's, I would provide a no steps left out look at how to build a Jeep inline six to the standards you desire.  The only obstacle:  This routinely maintained engine simply refuses to wear out!

 

Moses  

 
 
 
 
 

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