The "famous" connecting rod pic

[Bill Stockard]

PSD Powdered Metal Rods

Originally posted by JHardwick

This reminds me of a time I was looking around on the Powerstroke forum and those guys were defending the "powdered metal" rod. I never registered or posted, but one member actually had those guys believing that this was a "forged" rod and was stronger!



Powdered metal is far from a forging!

Quote from the "Power Stroke Register Magazine", Volume 6, Issue No. 1, Winter 2003, PSR Tech, page 117 & 118,



"... they are capable of 400 HP and 1,000 ft-lbs of torque with 40 lbs. of boost and fuel system. The trouble with that is the durability of the rest of the truck. The only thing contrary of that is late 2002; they switched to PM (Powdered Metal) connecting rods. These rods will take stock power level and more, but super high power should be left to the earlier engines with steel rods. "



Hmm, wonder why they say that... ?



Bill

 

[NSperduto]

Ok, the pic is nice, but...

Aren't the duramax and pds 8 cyl engines? and the CTD a 6 cyl

I would think that if you were building similiar displacement engines with two less cylinders, the parts would have to be bigger because the pistons are bigger. heck, everything would have to be bigger



While yeah, it's a cool pic, I don't think it really means anything.



Maybe I'm wrong.



Nick

 

[bighammer]

I had the same thought, but didn't post anything about it. The V8 will have a good bit less stress on each rod so they can be much smaller. Sort of like a guy in a 2 story house boasting that his foundation is bigger than that of a guy's ranch house, and then claiming his house is built MUCH better.

Originally posted by NSperduto

Ok, the pic is nice, but...

Aren't the duramax and pds 8 cyl engines? and the CTD a 6 cyl

I would think that if you were building similiar displacement engines with two less cylinders, the parts would have to be bigger because the pistons are bigger. heck, everything would have to be bigger



While yeah, it's a cool pic, I don't think it really means anything.



Maybe I'm wrong.



Nick

 

[DPelletier]

8 divided by six is 1. 33. I think its fair to say that the Cummins rod is much larger and stronger than 1. 33x the competition.



Keep in mind also that the 7. 3l PSD is 1. 24x as large as a cummins and the DM is 1. 12x as large.



But where I get all warm and fuzzy inside is when I realize that the diameter of the rod is larger, the thickness of the bearing surface is larger and we have 7 main bearings for 6 cylinders instead of 5 mains for 8 (an 87 percent improvement WITHOUT calculating the difference in the size of the bearings.



Sorry guys, I remain impressed!



Dave

 

[DPelletier]

What I'd really like to see is a comparison of the square inches of bearing surface between the three engines. I think you'd find that our engines have well over double the bearing surface. All other things being equal, with the same HP and double the bearing surface, we have a MUCH longer lived and stronger engine.



Anybody?



Dave

 

[Crunch]

Originally posted by NSperduto

Ok, the pic is nice, but...

Aren't the duramax and pds 8 cyl engines? and the CTD a 6 cyl

I would think that if you were building similiar displacement engines with two less cylinders, the parts would have to be bigger because the pistons are bigger. heck, everything would have to be bigger

Maybe it's the picture, but the Ford and Chevy rods don't look any bigger than what you'd see in a large block gasser. The Cummins rod looks like what you'd find in a farm tractor. Yes, there is more stress in putting similar HP on 2 fewer cylinders, but from the picture it looks like the Ford and Chevy rods are inadequate in and of themselves. Putting the Cummins rod next to them is just rubbing salt into the wound.

 

[rbattelle]

For those unconvinced

On a more technical level, I believe the Cummins rods show a more mature design. For example, the Cummins rods exhibit the following characteristics that are minimal or absent from the GM and International rod:



1. Larger bearing surface area.

2. Better fillet radii to prevent stress concentrations

3. Maximum size of the crank pin, as evidenced by the canted end cap (required to remove the rod from the block through the piston hole, I believe).

4. Maximum size of wrist pin.

5. Nonlinear radius of curvature on the upper edge of the crankpin.

 

[DIESELMAN]

Originally posted by Diesel Gunner

So, who is going to post a picture of the broken journal rods that are being used now? I have see photos of the ones used by Cat, but would still like to see the Cummins version.

Looks the same.



There are two ways to split the journal, if you bore the hole first, you cannot 'cut' the cap off because the hole will be missing metal the width of the kerf of the blade used to cut it, it will not be round. The bore must be machined after the cap is created.



Machining the cap in this manner adds several steps to the production process and actually results in a weaker connection because the machined surfaces align along long smooth shear faces.



A Split rod is machined first to near its finished form, then chilled and 'split' along a scored fracture. This results in a unique mating surface that is very rough and results in a very strong connection.



The rod is then final machine finished with fewer steps.



Angling the mating surface results in better loading of forces across the connection and less deformation of the journal during compression and power strokes. And makes it easire to fit in the block.



All rods bend like a toothpick between your fingers, these are more like a broom handle between your fingers.

 

[rbattelle]

Excellent explanation, dieselman!

 

[Diesel Gunner]

Thank you, dieselman, excellent explanation.



Now, is the surface between the rod cap extremely uneven and appear to be "broken" or is it a much smoother finish as say, the finish left behind when crystals are cleaved? I would love to see photos of the mating surfaces on this type of rod. I know that it seems that I am majoring in the minors here, but I am just curious.

 

[MAX A/C]

Rods for sale

If anyone wants their very own set of Cummins vs. Powerstroke connecting rods (1 of each), I have 3 sets for sale. See my classified ad under "Miscellaneous". Please email me directly with any questions.

Thanks.

Scott

 

[RobertBolinger]

I guess you sold them all-could not find them...

 

[MAX A/C]

Robert-

Well, I dunno why it's not showing (just placed it a few hrs ago). I placed the ad again to no avail. I can bring it up to edit it, but can't find it normally either. I remember reading somewhere it takes 24 hrs for the ad to show up. So hopefully by tomorrow at 10:00 MST it will be up... Thanks for your patience.

Scott

 

[jlasich]

When I was home in Washington on leave, I went down to the local Dodge dealer and inside they had all three conrods on display. It was pretty cool to see that at a dealership. Not sure if the Ford one was from a 6. 0l or 7. 3l, though. The picture posted on here with the 6. 0l rod is amazing. That thing is SO tiny.

One other thing I like to think about is the number of power impulses on each conrod journal. Cummins = one; PSD and Duramax each have to have two (two conrods share the same journal. ) That fact alone makes me believe the Cummins is more durable. Less stress.

 

[rbattelle]

I just received a B5. 9 connecting rod in the mail from a TDR member. All I can say is :--) That picture doesn't do this rod justice. The connecting rod is a well thought-out, well-engineer piece of metal. I am absolutely amazed. I worked a few years in an automotive parts warehouse, and I've seen lots of connecting rods. Never have I seen one this large for a passenger vehicle.



I was so impressed I just had to post. #ad

 

[MWBrooks]

Even Stevie Wonder could pick out the best rod in that picture.





Mike

 

[Vaughn MacKenzie]

Here's a 6L cutaway but it's hard to see the rods. What a jumbled pile of machinery



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[BIG BOB]

That picture I took really gets around!

I just wish I could fine a DuraMax and Ford 6. 0 to compare with the Cummins!

 

[rbattelle]

Re: That picture I took really gets around!

Originally posted by BIG BOB

I just wish I could fine a DuraMax and Ford 6. 0 to compare with the Cummins!

You're the one who took that shot? Brilliant. If they gave Pulitzer prizes for component pictures, you'd have my vote.

 

[rbattelle]

Here's a recent picture of the latest connecting rods. The Duramax looks like a nice gasser rod, but I'm rather impressed with the 6. 0's rods. I have a Cummins rod on my desk at work, and it's shape is slightly different than the one in the picture (it's wider in the mid-span region, and the end cap in the picture is MUCH smaller than the one I have). Notice the 6. 0 is wider than the Cummins rod along some of its length. It's hard to tell from a 2-D picture, but it looks to me like the Cummins rod is a little thicker than the 6. 0 as well. International certainly has taken a leap forward in connecting rod design. They've properly filleted their corners to reduce stress, and no one can argue that rod is way beefier than the old 7. 3 rods were. I am curious what vintage that Cummins rod is... for the 600 perhaps? My '03 service manual shows the rods are the same as the older Cummins rods with the wider midsection and larger end cap.



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