midwestdually

quality :

97CTD

Not to be negative fellas or call anyone a liar but that photo looks a little resized to me i wish it were more like the old one of the 6.5 chevy 7.3 Stroke and the 5.9 cummins just the 3 rods side by side with no fancy backgrounds or anything that makes me wonder

MnTom

I showed that pic to a diehard chebby fan and his reaction was "There is not as much torque in the chebby since it is a v-8 so there is no reason to build them as heavy". Out of the mouth of the uninformed........................

Berak

Of course to a certain extent that is true, each Cummins rod does need to hold 33% more of the forces than an engine using 8 rods. It looks to me that the Cummins rods are far more capable than only 33% more though. I would guess it would take 2 - 3 times more force to break a Cummins rod than a PSD or Duaramx. Anyone have that kind of information?

AlpineRAM

I may throw in my cents:<br><br>First the rods in a cummins must take much more than 33% over the V8 design, because they have to be much longer. So shearout is much more of an issue compared to the short rods. <br>Torque is made by a force acting on a lever. So a shorter lever (less stroke) will have less torque when having the same force on a piston. <br>There are a whole lot of other factors influencing the design of an engine. <br>Bigger=Better .... don't think so. <br>Just because there is more material it will not hold up to more power. Actually the greater the mass you have to accelerate the more force you will induce into the part just to move it. So this leaves less strength to transfer force from one end to the other. <br><br>About durability of powdered metal: I do work for some companies in the automotive industry supply chain. Actually the components made of powdered metal are much stronger for the same weight than forged material, if treated right. Especially in the application as a pushrod you can not allow the rod being bent a bit because if you have the start of a bend the rod will arc out and lose strength rapidly. Powdered metal that is surface treated forms a kind of skin that will hold the part together and makes the rod very stiff. The downside is that if you brake the skin you lose strength very fast. <br>A company I know bouilding pushrods for F1 and Superbike ad problems with PM rods that had fallen down on the floor during assembly. These rods broke very easily. (at less than 50% of max rpm)<br>At the pushrods usually you use a bearing that is made of another material and separate from the rod itself.<br>Some other parts made of PM are the whole geartrain for the VANOS on the BMW engines. <br>The only times I have seen PM pushrods fail were when either the engine had ben operated way out of the intended parameters, or when there had been a severe disfunction of the lube circuit. The rods do not stand up well when brought up to very high temperatures and applying force in a direction not intended. Since all these failures would have been catastrophic with forged rods too, I do not think that the PM rods are inferior. <br>Since they need very special care during transport and assembly, and can be harmed by scratches and cracks in the surface skin they are a bit more difficult to handle without detailed education. <br><br>Off the soapbox now<br><br>AlpineRAM

sherod

Alpineram, Thanks for the education on PM vs cast. I was wondering about the differences. Ed

AlpineRAM

Pleasure

I made a comparison between forged and PM rods. Cast rods are another topic. Usually cast rods are prepared for use by a blasting process to achieve a thin skin of compressed material. Some people refer to rods as being cast, even when tey are forged rods. Sometimes there is a kind of raw rod that's being cast, then re-heated and forged through several stages of drops. These rods still look like cast rods because the surfaces where you have your entrys and windpipes of the cast are of no great relevance for the static of the rod, so they are not forged.

I think that there are lots of materials that are an advantage but will be bashed by the shadetree mechanics because they do not know how to handle them. ( Think of Nylon washers for oil drain plugs and the comments about 15 years ago)

Personally I like my Cummins for the relatively easy repair on the mechanical parts.
I think that PM parts can be very good, but they are no way for engines that may have to be repaired on site.

AlpineRAM

Berak

AlpineRam,

You certainly seem to have far more knowledge than I about rod design. But with my limited knowledge I will still claim 2 points that you dismiss:

1) More mass holds more force, given the same design. Bigger doens't = better. Ok sure, let's put those super 6.0 rods in a submarine diesel, mass doesn't mean anything right? I understand why you say that because design is more important, but it just isn't true given equivalent designs. Do you feel the PSD rod can hold equivalent forces as the HO rod? Which one has the greater capacity for additional forces? (Higher hp / tq). I'd be willing to bet you whatever you'd like that the HO rod will.

2) PM rods exist in the real world, in the real world sh*t happens, I'll take the rod that doesn't rely on a special skin to maintain it's integrity thank you.

Sometimes things are engineered in a lab that doesn't take enough real world parameters into account. Stuff breaks and the enginners can't figure out why, when their simulations never did. :

AlpineRAM

Berak: <br>First: I didn't say that the pushrods of another engine maker are better or worse than the ones in a Cummins. I say that if you take a bigger rod you will have more static load you can apply ( = bigger piston, more pressure) but it will break at lower rpm than the lighter rod. )<br><br>Which rod has the higher capacity for additional forces ? I do not know and never claimed to know. I do not know with which initial reserve those were designed. <br><br>Making more hp or more torque: I can not blame an engineer if he designs a pushrod for a 300 hp engine that will hold 300 hp reliably. That's his duty. If it fails at 350hp it's not his fault. (Personally I bought the Cummins because it's bombable)<br> <br>What I do know is that PM rods are used successfully in several applications. I just stated that a scratch that will make them fail would not even be ignored by a forged rod. <br><br>I know of enough cases where things the engineers thought being good came out as being a massive waste of time and cash. <br><br>When I said that I do not think that bigger means better I did not imply that a.) smaller meant better, b.) size was no concern anyway c.) the pushrods of competitor a were superior- inferior to competitor b.<br><br>I bought a Dodge RAM 2500 with a Cummins ISB - not 6 pushrods from a submarine diesel, 6 cylinders from the Exxon Valdez (cheap to have) and the injectors from a VW Golf TDI for fuel economy. - ;D<br> <br>I am content with my engine. - I'd suggest that you go and upgrade all your engines with the heaviest pushrods you can get. Submarine diesels are quite small- go for tanker engines. <br><br>Actually this stuff must fit together and the whole package must fit the application. <br><br>I stated that the PM rods should not be used for engines that will be repaired somewhere in the field. <br><br>Now I'll quit ranting ;D<br><br>AlpineRAM

Berak

Ok, clam down man. ;D<br><br>I didn't try mean to try and put words in your mouth and get you all &gt;.<br><br>I was just trying to point out what I think is one of the benefits of the Cummins engine design is it's bombability (sp?) and that I think it's a stronger built engine, able to handle greater forces and levels of torque. This is mainly due to the inherint strength of the I6 over the V8 design. Larger rods are part of that design. The fact that the HO rods are not PM is also a good thing, although as you stated PM rods can be made to work in an acceptable manner.<br><br>I think we are in agreement here I must have misinterepreted your first post a little.<br><br>Peace! ;D ;D ;D

AlpineRAM

Berak: I didn't want to sound angered by your post. In situations like these I usually find out that English is not my mother tongue. I do have some problems with expressing emotions like amusement between the lines. <br>I do like the fact that the ISB is used for industrial applications and is available with much higher output than in the Dodge for lets say excavators ( 300 hp version ). Ant for these engines Cummins gives a nice long warranty, knowing they will run WOT 24/7/365.<br>Well now I can say that all the cars in my family are I6s ( Toyota FJ62 gasser 1989, Mercedes Benz 230 4spd auto prototype 1967, RAM see sig)<br>Maybe I am a little touchy about the bigger=better thingy because thinking like this is responsible for lots of damage I've got to correct all the time. <br><br>Peace is a very reasonable suggestion ;D<br><br>AlpineRAM