Odd Connecting Rod

[Heck]

I'm re-doing my stroker, and I ordered some kb944 pistons, so I decided to dig out my 2 sets of 4.0 connecting rods to see which to use. But when I look at them, I have 2 different sets. Six are the 544 casting I expected, but the other six are stamped 545, look more delicate and seem lighter. I know the 545 castings came out of my '03 rubicon because I took them out myself, but the FAQ only lists the 544.
Any Ideas what I'm looking at?

[SilverXJ]

Interesting... something new. Can' help you but some pics would be interesting. Why the two sets? And unrelated, how much did you pay for the KBs if you don't mine my asking.. I'm looking at a set myself.

[Heck]

Interesting... something new. Can' help you but some pics would be interesting. Why the two sets? And unrelated, how much did you pay for the KBs if you don't mine my asking.. I'm looking at a set myself.

I'll post pic tomorrow night.
Had 2 sets because on the first build, I wasn't going to bore the motor, but several pistons broke while pressing out the pins. I couldn't get a delivery date on any aftermarket, so I got a set of used stock pistons from someone off the strokers group, and he sent the 544 rods with them.
Buying mine from summit and if they ever ship, the pistons and rings set (kb944ktm030, I think) is around $550. If you were doing a stroker from scratch, I might be cheaper than it sounds since you won't have to buy connecting rods.

[SilverXJ]

When did you order the pistons? Summit stated like a two week wait prior to shipping... I hope it hasn't been more than two weeks... my machine shop said I can get a custom set of Wiseco pistons for $80 each, but it would take 3-4 weeks to get.

[Heck]

Ordered them last week, but Summit doesn't expect to get them in stock till the 14th or 15th.

[Mgardiner1]

i can't stand summit's "projected" dates. I had one that was projected to ship in 2 weeks, and then i received an e-mail that it was shipped out that night. Bonus on the faster time, but all other instances are annoying, because the date changes every day LOL

[SilverXJ]

i can't stand summit's "projected" dates. I had one that was projected to ship in 2 weeks, and then i received an e-mail that it was shipped out that night. Bonus on the faster time, but all other instances are annoying, because the date changes every day LOL

You are complaining that you actually received a part sooner than expected?

[gradon]

If you know someone at a machine shop or plan to use one, they can order the KBBs(directly) and get them cheaper(how you gonna use their services to press the rods on the pistons if you don't have pistons?).

[Mgardiner1]

Bonus on the faster time, but all other instances are annoying, because the date changes every day LOL

You are complaining that you actually received a part sooner than expected?

I said it was a bonus having it show up sooner then expected, but every other time the system seems to poorly estimate the actual dates

[Heck]

Alright- they're not 545, they're 548 castings. Quite different from the 544 rods, appear dimensionally identical, feel slightly lighter.

Edit- 544 on the left, 548 right.

[Mgardiner1]

Someone else can hopefully chime in with details, but just by the picture i'd want the 544 rod on the left! The wrist pin seems to be supported better, and the gussets on the big end seem beefier.

[yuppiexj]

Someone else can hopefully chime in with details, but just by the picture i'd want the 544 rod on the left! The wrist pin seems to be supported better, and the gussets on the big end seem beefier.

I did notice some core shift on the 544 around the wristpin, other than that,
The one on the left looks better, material appears to be removed from where not needed
The gussets look stronger on the big end.

I wonder if DCX made a change before the end of the production run.
A 1 gram change saves 6 metric tons of iron on 1 million engines (1g x 6rods per x 1Million engines).

more pondering is in order.

[SilverXJ]

I've also seen rods on ebay and other places labeled as 641 for the 4.0L engine.. anyone know about that one? I don't think we have enough information on the 4.0L rods primarly due to the fact that they weren't used heavily in a stroker until recently with the introduction of the KB944 piston.

[1bolt]

How about a 691... Came in a 2001 Grand Cherokee block (53020569). Chris this is the same block that I showed you that the Guy from Jersey wanted to buy but kept pestering me about so I falsely told him it was a TJ block just to get rid of him. I finally got some free time and tore this down the rest of the way... Yeah when I get free time I go get greasy... No much is more therapeutic than Hauling off on a Harmonic balancer puller, or the satisfying *crack* when you take the torque off rod bolts and mains.



Looks a lot like the other rods, but the "I beam" portion as it flares to the big end is much thicker than the 544 might be a stronger rod than the 544...

I'm guessing but these might also simply be different suppliers providing slightly different castings that all meet Chrysler standards and costs requirements.

For what its worth (2 cents give or take, probably 1 cent given the economy) I'm inclined to think that the 548 may be the better rod... For starters I don't agree that the outward proportions of the rod are a good indicator of strength... At the big end the gusseting on the 548 is clearly a larger slower radius, with more metal in the actual gusset. The tighter the radius the weaker any gusset is and the 544's are tighter. At the other end and having looked at two I have side by side... the 548 has smoother and again longer sweep to the radius. The two sides of the "I beam" (if you want to call it that) meet in a mild smooth V shaped arc (whereas the 544's small end doesn't have much radius where the I beam meets the pin. The outsides trail around in a smooth radius on the 548... Where as the 544 the I beam is very thin at the big end, and even though its thicker as the wrist, the I beam doesn't meet in the middle with a radius and the outside also doesn't wrap around the wrist pin in a nice radius. The 548 wrist is slimmer in outward proportion but also thicker in cross section more metal coming together...

To me this means more metal at the bottom of the pin where its needed most: Where the most rod stretch happens and also where the most downward force is focused by the pin... I bet if you cut both rods though the smallest part of the wrist the 548 would have much more cross sectional area, its just packed closer together.

The casting is also much smoother (less stress risers) which also could indicate a better alloy used. Or just better casting technology. I believe the 548 is both lighter, better designed and better cast. And I have no way to prove it so take it for what its worth.

This type of thing is what I bought the Mopar Jeep Engines book for but I don't recall any insider detail goodness about the factory rods.

[SilverXJ]

Interesting. There is a lot of speculation and undocumented items on the later model 4.0L. Too bad I already purchased a set of 544a. Exactly how would one scientifically determine the strength of a connecting rod?