Connecting Rods.

[CRASH]

On a scale of 1 to 10, (when compared to other foreign and domestic con rods), where do 4.0 con rods rate?

The thing that scares me the most about building a stroker is reliability. I range far from home on a regular basis, and I don't want to throw a rod 100 miles from the nearest paved road.

Are there aftermarket rods available? Are they worth the extra cost over the OEM units? And just how the hell does a shop resize a con rod, and what effect does that operation have on longevity?

CRASH

[RCP Phx]

Resizing is easy,they grind the caps and then rebore the center.Ive never looked into engine parts but you could always polish and then shotpeen the stockers along with some ARP bolts.

[XJZ]

Just go with Accurate or Hesco. You'll know they're right on and not have to worry about it.

You can spend your time working on fabulous new products. :cool:

[CRASH]

Since my rig is the rolling catalogue of U.R.F. Inc. products, it has to be built right!

CRASH

[Eagle]

The 4.0L rods are stronger than 4.2L rods, but also longer. If using the Accurate Power (or other) custom pistons this is not a problem. If trying to use stock pistons, the 4.0L rods will put the top of a stock piston at or above the top of the block. Not good.

Aftermarket rods are available. Check in on the Strokers group -- within the last couple of days someone posted a name and a source. Also available from Hesco ($$$$$$$), and from Clifford (????? Quality).

Let's look at this objectively. The 4.2L engine has a longer stroke than the 4.0L, weaker rods, and has been around since about 1970. These engines have been used in everything from drag racers to autocrossers to police cars to taxis to postal trucks. How many have you ever heard of breaking a rod? And the 4.0L rod is stronger.

IMHO, unless you plan to run very high RPM, or very LOW RPM under extreme loading, custom rods are a waste of money. Get a good set of 4.0L rods (buy new if you're really worried), have them shot peened, and go wheeling.

[xjjunkie]

i sell the eagle I-beam rods for $159.50 they come with arp wave-lock bolts, and custom pistons for $500.00

scot

http://www.imagestation.com/picture/sraid42/p7c806fbfe9ecab00b42e83ed7804c22c/fcefc724.jpg

http://www.imagestation.com/picture/sraid42/p65e4157ab1367ce6c8749ef773a99aec/fcefc738.jpg

[CRASH]

Scot,

Are the pistons dished to return the proper quench to the motor? Sounds quite interesting.......

CRASH

[XJZ]

Scot, more info please. Who makes the pistons? Forged? What about the I-beam rods? Details. Oh, by the way, expect a call from Eagles copyright attorney about your clever name for the connecting rods. :)

[Eagle]

Scot, is that $159 per rod, or for the set?

[Eagle]

Originally posted by CRASH
Scot,

Are the pistons dished to return the proper quench to the motor? Sounds quite interesting.......

CRASH

Quench is a function of rod length and pin height (basically, clearance between the head and the top of the piston), not dish. The stock 4.0L engine is technically not "quench compliant." What you are probably trying to ask is: if the custom rods and pistons result in a quench compliant piston height, are the pistons dished enough to bring the compression ratio back down to (or near) stock CR.

[MudDawg]

Are those rods in stock 4.0 / 2.5 lenght??? or are they short like the 4.2 rods??? I'll take my motor back apart to install real forged rods. I need the 4.0 / 2.5 lenght rods. I am running shotpeened stockers with good bolts right now..but the motor loves to rev..I have it chipped at 5500, I'd like to keep all the parts in the right places for as long as possible.



Quote from the Schnitz Racing cataloge...All parts have a lifetime...racing parts have a shorter one.

[CRASH]

Inquiring minds want to know.

Eagle, when it comes to engine stuff, I'm a dope. Your correction is much appreciated, and your description of my desire for correct compression ratio at a decent quench height is right on.

Give up the info, xjjunkie.

CRASH

[xjjunkie]

i mansge a speed shop in YORK, PA. have been a venolia dealer for more than 25 years, also a dealer for eagle products. the pistons are custom made by venolia, and the rods are eagle I-beam rods. the rods are $159.99 for a set of 6 rods. they are new, matched weight sets, have ARP wavelock rod bolts in them, the little end or pin end is a floater, meaning it has a bronze bushing in, so you have to use a piston with a locking wrist pin (like the venolias. rods are avalible know, pistons are 3 to 4 weeks out.

scot

[CRASH]

If you assemble your con rods and pistons on a 4.2 crank, what is the final assembled compression ratio, and is the quench correct?

CRASH

[Eagle]

Crash --

FYI, Ben "Stroker" from the NAC has been running an Accurate Power 4.6L engine since before the chapter was formed, and that was 3 years ago. Ben is, shall we say, not known for having a light right foot. He hasn't broken his yet ... therefore it is exceedingly unlikely that you could break one. I'm pretty sure Ben's engine uses the 4.0L rods with Accurate's forged pistons.

[ChEwBaCcA]

We have a guy in a local club that bought an Accurate power stroker and it blew up in less than a few mins! So not everything Accurate touches turns to gold. The Piston went into the head and the rod came out the bottom of the pan! This was on a complete motor built and assembled by Accurate.

They have been good about replacing it but, he had to ship the motor back and have them look at it and the turn around was not real fast if i remember correctly. Not baging on Accurate but a F*&^ up like that is 100% unacceptable in my book for the money he spent......and of course his time! I cant understand how someone makes a motor like that and doesnt check the clearance between the top of the piston and the head.....

Regards
Chewy

[Goatman]

I'm interested in the same stuff. I bought a used (25K, 1 yr old) 4.6L very budget stroker, pretty cheap. It has stock 0.30 over pistons and 4.2L rods, with a compression ratio of 10 to 1. It's a Renix, so has the knock sensor, and he must have been fighting ping because it also has an adjustable MAP sensor.

I want to tear it down to inspect things before I put it in my rig, and I want to replace the pistons to correct the compression ratio. I'm wondering if there is enough of an advantage to spend the $$$ for 4.0L rods and custom pistons, verses just getting a set of the Silvolite 4.0L pistons and having them dished to the desired compression ratio. An advantage to me is a long life for the motor, overall increased reliability, and a guarantee of the proper quench height.

For you motor heads out there, when I get to tear this thing down, how do I determine what quench height I have, and what are the ways to correct it if it's wrong? How do I determine if this block has already been decked or not, and if so, how much?

One other thought that I've had through all of this stroker talk. The 4.2L motor, based on my experience and observations, is a 130K to 150K motor, before rebuild. The 4.0L motor is generally a 250K to 350K motor before rebuild. Why??

[MudDawg]

Quench clearance is basically the distance between the piston and the head...(we are dealing with flat top pistons) measure the deck height...measure or obtain the compressed thickness of the head gasket you will be using..if the pistons are below deck...add that amount to the gasket thickness... If above deck subtract the amount from the gasket thickness...around .040 is a good total clearance...I ended using a copper gasket from Clifford Performance because the stock gasket was too thick....one possible alternative to custom pistons, assuming you can get the deck height right is to have the pistons fly cut in the bowl area to bring the C.R. within range..

Poor quench can result in pockets of excessively rich mixture which aggrevate the preignition...also be sure that the entire combustion chamber including the valves and piston tops are deburred to smooth any sharp edges...I even spend a few extra minutes to deburr the electrodes on the plugs.

At least we arent dealing with poor plug placement or piston domes that inhibit proper flame propogation.

[xj4rocks]

Originally posted by Eagle

Let's look at this objectively. The 4.2L engine has a longer stroke than the 4.0L, weaker rods, and has been around since about 1970. These engines have been used in everything from drag racers to autocrossers to police cars to taxis to postal trucks. How many have you ever heard of breaking a rod? And the 4.0L rod is stronger.



Of course my 4.0 threw a rod (or 2?) driving down the road going home for spring break the other year. :)

[CRASH]

Yes, throwing rods is my concern as well, our Sierrqa Chapter Prez threw a rod in his rig on level ground turning like 2200 rpm. These forged rods sound like a nice upgrade, and the price is very good.

xjjunkie, can you post a pic of one of your connecting rods in side profile, and give us some specs?

same with the pistons.

CRASH

[CRASH]

Here's what I found during a google search, these are 4.2 rods:

Manufacturer: Eagle
Mfg part #: CRS6150A3D

Eagle "ESP" H Beam Connecting Rods Feature:
2-Piece forging for increased strength
Silicon bronze bushings for floating pistons
Multi-stage heat treated
Packaged in weight matched sets
Certified 4340 steel, vacuum degassed to remove impurities
Each forgins is x-rayed, sonic tested, and magnafluxed to insure quality
All surfaces are 100% machined
Shot peened to stress relieve the metal

Specifications: Crank Pin Piston Pin B.E. Width
2.095 .912 1.063

C-C Length Notes Gram Weight
6.150 +.025 660

CRASH

[FarmerMatt]

Andy, those are the same rods that are in my high priced stroker. The pistons are custom JE's.

Matt

[CRASH]

Yes, well, you're the one to blame for my current stroker obsession. Did you change out your injectors yet? Still running a bit rich? Are you running 91 octane?

You're lucky you weren't around when Jes and I were test driving this: http://www.fototime.com/{D8E60B5F-6E46-4CEE-90E3-F8A78297C95A}/picture.JPG

The 351 stroked and bored to 427 with a mass air fuel injection system kept a very nice smile on my face. It was the most powerful 4 wheel drive vehicle I've ever driven. You would have had to have one!

CRASH

[Eagle]

Goatman, keep in mind that the stock 4.0L is not quench-compliant. Anything you do in that direction is an improvement.

[FarmerMatt]

Yea I read you guys got to joy ride that beast. I would have killed to be there. No I'm leaving the injectors alone. I'm afraid that if I down size I could have more pinging problems than I do now. When it's real hot out & I lug the motor it will ping, but it's also 10:1 compression. If I ever do anything to it I will change out the pistons & lower the comp. I am running high octane & also played with some octane boosters to see if that would cure the problem completely, but it didn't. It's not bad, but it's there & I'm anal about my junk running perfect so it bugs me. The question will be if it passes smog with the big injectors or not.

Matt

[CRASH]

Yeah, I'm anal about having my junk run and look perfect as well. ;)

CRASH

[Ed A. Stevens]

Quench is the distance between the piston crown "quench band" and the flat "quench band" on the head surface. Anyone who has wrenched on two-strokes will recognize the shape match of the piston and head quench band.

A quench compliant design is much more common than expected (early closed chamber SBC/BBC's are quench compliant with flat top or dished pistons), but the research on why it works well is less than 20 years old. The research came out of engineers working the other direction, with domed pistons and wide TDC combustion chambers, and finding the designs were limited with respect to power and emissions performance. The limitation was detonation and poor gas charge ignition of the wide TDC chamber, issues that a compact concentrated TDC chamber volume solved. The tight perimeter quench band clearance provided the concentrated TDC chamber space that solved the problems with emissions and power. The same principle of a quench band and tight combustion chamber space is applied to polysphere and pentroof chambers (new Chrysler Hemi and Ford OHC engines) and modified wedge chamber designs (ones like the 4.0L and Vortec engine designs).

Honda took the concept further in the late 70's and added a primary ignition chamber in the head, with a secondary quench compliant chamber interface between piston and head, allowing them to avoid catalytic converters and still meet pre-OBD emissions. Now converters are so cheap only the quench compliant chamber is retained.


With the head off the block, measure from the piston top to the block deck. Add this distance (down the bore, or above the deck surface) to the compressed gasket thickness. This is the quench height or thickness. The range where detonation is less common is 0.035-0.070 inch (quench compliant), and 0.110 or more (non-quench compliant).

The stock pistons are well down the bore in a 4.2 rod budget stroker (0.030 - 0.040 inch). Add this to the compressed gasket thickness (0.042 or 0.060 inch) and the result is a wide 0.070-0.090 inch clearance. The detonation promotion range is from ~0.070 to 0.110 inch, right where the budget stroker ends up without block decking.

The difference in stroker engines block decking and head shaving, and fuel quality in different localities, have resulted in a wide variation in success and problems with the budget stroker. To find what you have, measure the distance the piston sits in the bore at TDC.

Where the builders took time to clean up the chambers (the old polished chamber of hot rod lore) detonation problems are reduced, and where fuel quality is great the problems are reduced. The Renix engine management with the knock sensor can retard the timing to reduce the detonation (with a slight impact to power).

The known solutions are to block the deck to reduce the quench band clearance below 0.070 inch (tighter is better) and adjust the Compression Ratio (head or piston dish size increase).

The stock replacement pistons that have been successfully cut for a larger dish chamber are the cast HU KB-Silvolites, or forged pistons (AP, Venolia, J-E and others). The majority of forged pistons are designed for the longer 4.0L rod, although Greg Friedman's MJ is running forged J-E pistons with a custom dish design and the short 4.2 rod (a semi-budget quench compliant stroker that runs on 87 octane).


The major difference in 258 and 4.0L rod life is lubricant quality, engine temperature & controls (emission controls), and maintenance. Modern lubricants are much better at reducing sludge, acids, and other contamints that reduce engine life. Modern emissions controls keep the crankcase charged with filtered clean air (when the CCV system is not defeated) to reduce contaminints. Modern engine temperatures (185dF+) reduce sludge and unburnt components of combustion to keep the crankcase clean. The fuel injection systems do not wash down the crankcase oil with fuel the same way the carb systems do on a cold start. The maintenance of most 258's used for off-road usage is questionable.

The 258 engine reliability record is actually good considering the severe duty abuse most of the older Jeeps would experience. Include the light duty 258 experience in cars (from Pacers to Javelins) and the reliability is quite good (the same 300k miles we see on XJ 4.0L's).

I have no reservation concerning the use of a 258 rod in a stroker. When I was young I helped rebuild a 258 with over 500K miles and the bottom end was standard stock with new bearing inserts (A Scout that ran on propane as a rural mail delivery truck). The 258 engine design is reliable and strong.

Yes, a 4.0L rod is stronger and an Eagle rod is better, but even the 258 rod is as good as a cast Pontiac or Olds rod (or the typical modern engine cast nodular iron rod). The selection consideration would have to be rpm range, use the better rod for higher rpm usage.




Originally posted by Goatman


For you motor heads out there, when I get to tear this thing down, how do I determine what quench height I have, and what are the ways to correct it if it's wrong? How do I determine if this block has already been decked or not, and if so, how much?

One other thought that I've had through all of this stroker talk. The 4.2L motor, based on my experience and observations, is a 130K to 150K motor, before rebuild. The 4.0L motor is generally a 250K to 350K motor before rebuild. Why??

[Eagle]

Originally posted by Goatman
One other thought that I've had through all of this stroker talk. The 4.2L motor, based on my experience and observations, is a 130K to 150K motor, before rebuild. The 4.0L motor is generally a 250K to 350K motor before rebuild. Why??

No reason -- that's not an accurate statistic. Remember, I've been playing with AMC stuff since several years before it was AMC (I grew up driving and working on Hudsons). My brother and I have both had 199s, 232s, and 258s (4.2) in a variety of Rambler Americans, Hornets and Gremlins. We raced them, autocrossed them, and traveled all over the northeast with them, generally cruising at 70 to 75 MPH in the days before we had OD transmissions, and they were good for well over 150,000 miles. The record (as far as we know) goes to my brother's 1970 Gremlin 232 (3.8L). After beating the snot out of it and winning innumerable autocrosses, he bought a '74 and sold the '70 with around 180,000 on the clock to one of the auto parts stores we dealt with. They used it for a parts runner. Last we heard of it, it was over 340,000 miles and the head had never come off. And I'm sure you know that the kids who deliver parts for those stores do not give a rodent's posterior how they treat the vehicle.

While I don't accept the validity of the question, to whatever extent it may apply consider that most of the 4.2L (and 3.8L) versions were/are in vehicles that didn't have OD trannies. City driving doesn't generally involve overdrive, but I certainly think it's safe to add at least 10% to the number of revolutions an engine sees over it's life if the vehicle doesn't have OD ... maybe 15% or more for a lot of highway driving. And I think it's also safe to postulate the the XJs with the extremely high mileages generally ran up a lot of those miles in highway useage, in overdrive.

[xjjunkie]

here is a pic of the eagle i-beam rods. 6.125 c/c length, bushed pin end, arp 3/8 waveloc bolts, shot peened, +/- 2 gram matched in weight, x-rayed, sonic tested, magnafluxed, made of 5140 forged steel, rated to 500 HP. (.912 pin dia, 1.063 big end width, 2.095 crank pin) all of that for $ 159.99

scot


http://www.imagestation.com/picture/sraid71/p7e7492b06b7ec56351d9f3c0fb3010b0/fb979881.jpg

[offroadman83]

:eek: :D Gotta get me some of those. hehe!

[Goatman]

Ed and Eagle, thanks for some good info on 4.2 reliability. You both make good points about carbs vs. EFI, better crankcase ventilation, and non-OD trannies. My experience is with CJ's, so I imagine that they might get a little harder use, and do not have overdrive, I'm glad to hear you have different experiences. I was wondering if there was any reason, regarding long term reliability, to go with the longer 4.0 rods, but it appears that it is not an issue.

I want this engine to be reliable and perform reasonably well, with no hasssles to deal with. I hate to spend money needlessly, but if it would be worth it to change rods and pistons, I would balance the benefit against the cost. I do want to change pistons to get the CR down, but a couple hundred $$ for properly dished stock pistons is way better than $600+ for forged pistons and 4.0 rods.

Since the 4.0L is not quench compliant, will the budget stroker run fine if the compression ratio is brought down to the level of a stock 4.0L? I would much rather dish the pistons enough to have an 8.8 to 1 compression ratio than mess with any pre-ignition problems.

[Eagle]

Richard --

Bob Salemi in Rhode Island just put his stroker on the road. I believe except for a lot of head work he did himself his adheres to the "budget" formula, but he started his long before most of that info was readily available. If you want to contact him for some real-world answers, lemme know. I won't post his e-mail "en claire" but I'm sure he wouldn't object if I send it to you by e-mail or PM.

[Eagle]

Originally posted by xjjunkie
here is a pic of the eagle i-beam rods. 6.125 c/c length, bushed pin end, arp 3/8 waveloc bolts, shot peened, +/- 2 gram matched in weight, x-rayed, sonic tested, magnafluxed, made of 5140 forged steel, rated to 500 HP. (.912 pin dia, 1.063 big end width, 2.095 crank pin) all of that for $ 159.99

Those look so nice I'm almost tempted to build an engine just so I can have an excuse to get a set :D

[Goatman]

Thanks, Eagle. Doesn't he participate in the strokers list? Since the subject came up, I had a few questions, and will continue to check things out. However, I probably won't mess with getting the new motor in until this winter, and I can hit the stroker list with any questions that I have. I will take his e-mail addy though if he doesn't mind.

Like anyone else, I have two issues.....time and money. Both are in short supply right now. It looks like I need to get that thing out of the other XJ, pull it apart, and get some measurements. Then I can figure out what I want to do......and how much I need/want to spend.