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Discussion Starter #1 (Edited)
My plans for 2009/2010 include building a competition tube buggy. I won't get into that aspect too much here - just that it is the intended purpose and eventual home for the engine I will be building and showcasing in this thread.

I am planning on choosing parts looking for reliability (so I can beat the living snot out of it..) rather than all out power - although I expect to make 300 HP.

As well, I am frankly getting sick of the persistent myths surrounding the parts selection involved in building Jeep I6 stroker engines. Maybe I can share some of my experience with these engines in this thread as well.

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The Block:

I chose a well seasoned Renix (AMC) block for this engine build. This engine came out of a friends 1988 XJ. The reason for choosing the Renix casting is two-fold; 1) The pre-Chrysler AMC 4.0L castings are reputed to have a much higher nickel content then more modern offerings, making them in theory a tougher engine - less prone to distortion and premature bore wear, and 2) This 1987 block had a total of 200K miles on it at the time of "early retirement" - making for many many cycles of heating and cooler - and ensuring a well seasoned block.

It was tanked, line bored, punched out to 0.040, and decked dead flat. It also (of course) received new frost plugs and cam bearings:



This is what I meant by "early retirement" - the donor engine was hydro-locked prior to me getting it as core. It also had 3 rods that were broken:



In keeping with my simplicity and strength theme - the bottom end gets studded with ARP bolts from Bennie at Hesco http://www.hesco.us/shop.asp?action=details&inventoryID=42905&catId=7757. The goal is to have an engine that will take some serious abuse while foregoing critical failure:



I had to include a picture of my preferred bearing lube, Clevite 77. My machinist won't warranty anything unless it is installed with this shite. Must be good, and has to be better than plain old engine oil.

 

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Discussion Starter #2
The Crank:

Ok, I'm probably going to get some serious flak for this but the crank you want when building a I6 stroker engine for ANYTHING (grocery getting, rock crawling, mud, sand - whatever) is the 258 4 (four) counter-weight version. The 12 counterweight is an anchor.

The four counterweight version revs much faster, and smoother, and balances out much more easily. The 4 counterweight version weighs 20lbs less than the 12 counterweight version, and 10lbs less than a 4.0L crank! The lighter your rotating mass - the more power you can make. Simple. Ever wonder why racers lighten cranks?

For this build I used what I had. I didn't have the BEST version of the 258 crank (casting 3727) which requires no mods to the snout - I had the next best thing, the 3235477 casting. Same total weight same number of counterweights, just needs a 10mm spacer under the crank bolt:



Here she is, all studded up, nested and seated:

 

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Really interested in this, always been curious about 4.6 setups.

EDIT: Plus you always have great tech info to add to stuff, so this should be good :smokin:
 

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Discussion Starter #4 (Edited)
The Cam:

I have had much success with Comp Cams over the years with the Jeep I6 engines. The one I usually recommend to guys running factory fuel injection is the 68-232-4. Works well for most applications, but gets a bit flat in the higher ranges. Nice bottom + mid cam.

In my 400+HP I6 stroker turbo-charged Jeep http://www.pirate4x4.com/forum/showthread.php?t=614289, I run the Comp 68-201-4, as it is relatively mild and somewhat resembles a stock grind (serious turbo engines like stock-ish cams, counter-intuitively). Works right up into the redline.

For THIS engine, I expect to regularly take it up into the 4000+ range and hold it there - I need a screamer cam. I am using Comps 68-239-4 cam. It is the most aggressive one in the lineup, with lifts over 0.500 and made for mid to top end - it should fit the bill for this competition engine.

In she goes:

 

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i was just thinking about a stroker today and then you post this, i dont know to much about strokers, or engines for that matter, and dont want to clutter your thread. i know to search but are there any articles you have read that really stand out as incredible you would recommend?
 

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Discussion Starter #6
i was just thinking about a stroker today and then you post this, i dont know to much about strokers, or engines for that matter, and dont want to clutter your thread. i know to search but are there any articles you have read that really stand out as incredible you would recommend?
Not really. There is much contradictory and confusing information - I can't honestly recommend one single source. I will be taking this right through to the fuel system, so stay tuned.
 

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i was just thinking about a stroker today and then you post this, i dont know to much about strokers, or engines for that matter, and dont want to clutter your thread. i know to search but are there any articles you have read that really stand out as incredible you would recommend?
read the threads by YJ_and_Corey, hid info on I6 engins is amazing.

defenetly gona keep an eye on this thread. you do some sick work. subscribed!
 

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Thank you for doing this. I wanna do the stroker like this one once I can find an engine guy to do the work. What year is the 4 weight? I have a crank from an 89 YJ. I thought it was 12 weight but not sure.

Are you going to run 87 or premium?
 

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I am using Comps 68-239-4 cam. It is the most aggressive one in the lineup, with lifts over 0.500 and made for mid to top end - it should fit the bill for this competition engine.
...and just when I thought I was pushing a big cam with a Lunati at .484/.507 in my stroker!!!

Interested in seeing how you put this one together.
 

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Discussion Starter #11 (Edited)
Thank you for doing this. I wanna do the stroker like this one once I can find an engine guy to do the work. What year is the 4 weight? I have a crank from an 89 YJ. I thought it was 12 weight but not sure.

Are you going to run 87 or premium?
You will find the 4 weight cranks in 1981/2 to 1990 AMC 258 engines. If you haven't built your stroker engine yet - use the 4 weight crank.

The MOST desirable ones are the YJ ones (87-90), which are a true "bolt-in" to a 4.0L block, casting 3727. The other 4 counterweight crank was found in AMC products from 1981-1986 (the one I am using), it needs 10 mm shaved off the nose to accept a 4.0L harmonic dampener, or a spacer installed (my choice). The YJ ones seem to need less time on the balancer to balance out, in my experience.

As far as fuel is concerned, I really don't want to reveal what I am planning yet. It may be something new - I haven't seen/heard of anyone doing exactly what I am planning. The key is reliability - for the buggy this engine is going in as well.
 

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Discussion Starter #12
...and just when I thought I was pushing a big cam with a Lunati at .484/.507 in my stroker!!!

Interested in seeing how you put this one together.
Which valve springs are you running? Specs please.
 

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Which valve springs are you running? Specs please.
12499224 - GM Valve Spring Kit- 2001-2004 LS6 Gen III Engine- Set Of 16
Detailed Description
* Beehive style springs
* 1.800" installed height @ 90 Lbs pressure
* Set of 16 - 12586484
* Used on LS2 / LS6 heads
* Max lift .570"
* 1.250" Height, 295 Lbs pressure

The "yellows" have a lower seat pressure than the Comp Cams 26915-12's ([email protected]) but have a slightly higher spring rate, so they are better suited for aggressive cam profiles. I machined the spring seats for an installed height of 1.800" and used the Comp Cams 4930 height micrometer to verify.

I'm using the stock LS6 retainers and Comp Cams 623-16 valve locks. Roller rockers are Harland Sharp S40196A 1.6 adjustables. Pushrods are Crower but are discontinued.

Valves are from Racing Engine Valves and are stainless 8mm LS6 units, backcut and swirl polished and only $7.25 US a valve!
Intake: # PR2095 2.020" x 4.930"
Exhaust: #PR2090 1.570" x 4.930"

I used a seasoned '93 7120 head with some unique Serdi valve and bowl work, but if I do it again, I'm going to use a bare Alabama CH's 0331 casting for it's higher ports. Block is notched as well to reduce shrouding.

Hope that helps.
 

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Discussion Starter #15
The Rings:

I chose a set of Plasma-moly rings from Hastings, PN 2M 5506 065. These are actually Chevy 283 V-8 rings, but share the same 3.875 bore as a 4.0L. I have found that moly rings really break in quickly, and are worth the extra money - for piece of mind alone. I always use file-to-fit rings to make sure my gaps are perfect. It's the little details where power is made.



If you have the time, the patience, and the expert "file-to-fit" equipment I have....



.....you can get amazing consistent results. In my last engine, a turbo specific engine - my top ring gap was set at the extreme end of 4.0L spec (0.0250) in order to deal with the huge heat factors involved in turbocharging. A big ring gap means more room is available for thermal expansion.

This engine will run a cooler-burning fuel than gasoline, and doesn't require a huge ring gap BUT when I am racing I want overheating protection. Therefore I chose a top ring gap of 0.0150 (midpoint in the specs) and a second ring gap of 0.0280 (again midpoint in the specs).

Here is a top compression ring - as it came out of the box. There may be maybe 0.0005 gap. I just check to get a baseline:



Here is the same ring filed to 0.0150:



Here is my expert grade, high end deburring equipment :D:



Each time I finish a hole, I leave the rings in the bores. Each ring is ground for each bore, so it would be a minor disaster to mix them up:

 

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Discussion Starter #16 (Edited)
The Pistons and Rods:

I am going to get more flak for this, but if you can afford $100/hole for pistons, you NEED to run the longer 4.0L rods. The short 258 rods rob you of power and longevity. The long-rod stroker IS the better way to go.

It used to be that the only way to run the longer 4.0L rods in your stroker was custom, made to order pistons OR modifying a set of 4.0L slugs. Not anymore. Keith Black has released a series of pistons specifically designed to allow the engine builder the ability to run the longer 4.0L rods in a Jeep I6 stroker engine. KB 944 and 945.

The 4.0L rod is not only longer, it is stronger. A longer rod means that the "dwell-angle" of the piston against the cylinder wall is decreased, and it (piston) also stays at TDC longer. These are both very good things.

In my engine I am using 4.0L rods topped by KB Silvolite 944 forged pistons. These pistons, combined with my decked block (always set your 4.0L to zero deck clearance for maximum jam), will give me almost 10:1 compression.



Studded with ARP rod bolts, balanced (see bottom of rod), and re-sized:



Lighter pistons (like all rotating assembly) make more power. These pistons from KB are not only very strong, they are very light. KB also did away with the offset pin that the factory built every 4.0L piston with, so these pistons will be loud at startup, but with a centered pin should make some nice bottom end torque and have top-end stability. Note the size difference between the KB piston on the right, and the stock 4.0L slug on the left:

 

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what is your estimated cost for this build, and how much do you think it would cost if it were more on a budget? really great tech and im learning tons keep it up your last engine build was great
 

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sub.

great info cant wait for the pay off
 

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Discussion Starter #19
what is your estimated cost for this build, and how much do you think it would cost if it were more on a budget? really great tech and im learning tons keep it up your last engine build was great
This engine (minus the air/fuel system, which most people reuse anyhow) cost me $2600 Canadian, so about $2210 USD at todays exchange. It is a bit of a budget engine IMHO, due to the fact I reused many stock parts (I save the money on the assembly labour). Note that for the same engine, Hesco wants over 5K.

To drop the price, run 258 rods and cast 4.0L pistons, and forgo all the balancing - you will probably end up around $1500.00.
 
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