I really value the input I get from this forum. I need some advice....


Actually, SCAT is probably not responsible for this problem, I am 98% sure the machine shop did this. But when I took these rods, pistons, and pins to the machine shop to get them assembled, one came back with some dis-colorization (about 2/3 up the rod). It looks like someone took a torch to it. I called the machine shop and they said they have a furnace that they put the rods in to heat them up so they can put the pin in. Usually they don't discolor them like that. They also stated that they did not use a torch. The machine shop said this should be ok. I'd rather hear that it will be ok. Even then, I am still concerned. I've read that heating a rod past 300 deg F is BAD and can change the material properties of the metal. Not something you want on a highly loaded component such as a rod. What do you think I should do?

 

If the rods are forged heat treated then I think they should be fine with whatever heat was used since remember and engine gets problably 300 degrees or more. If they were cast rods with no heat treat then maybe there's an issue but again how high could they have heated them up? My 0.02

 

^^don't forget to vote^^

 

Replace the rod. Eagle suggests the same.

http://www.eaglerod.com/index.php?op...d=30&Itemid=25

 

Thanks for that!!!

 

What I suspect happened is after they took the rods out of the oven, that one probably was being stubborn so some dumb*** heated it with a torch to get it to go. I never will know what really happened probably but I think they should buy me a new rod, or at least when I get my new rod, they should assemble it for free. Then again, not sure if I really want to do business with them at all now...

 

No problem. It's not worth the risk.

 

Man you got that right!!!

 

I suppose Eagle's published technical papers might be a bit more authoritative than my own opinion, but I have seen literally dozens of connecting rods discolored like that from pin installation and never heard of one breaking in two...

Additionally, every motor that I have ever built that was going to see consistent +6000 rpm speeds had floating pins, where I didn't have to worry about Bubba at Joe's Automotive Machine melting my rods to install the wrist pins.

If that were my motor I'd run it. I think if you make a big issue out of this you're making a mountain out of the proverbial molehill. My $1.380

 

There is probably some truth to what you are saying. Chances are, there won't be a problem. But from a mechanical engineering standpoint I know that you never want to mess with the heat treat on a component once its been heat treated. Particularly one that is highly stressed. If I had "bought off" on a component such as this at places I have worked in the past (I am a mechanical engineer) my boss would have strung me up by my *****, guaranteed.

What I am thinking of doing is approaching the machine shop and giving them the benefit of the doubt, but ask them to meet me halfway. I buy the rod, they re-press the pin for free. I think that is fair. After the expense and effort that goes into building a motor, I just don't want to take any chances. One rod isn't that expensive.

 

We have some common ground here. I'm not an engineer, and I'm not currently staying at a Holiday Inn Express (Residence Inn...sorry) but as a Planner/Estimator on military aircraft I work with engineers on a daily basis, and I spent many years as a structures/ sheetmetal guy who had the pleasure of executing the schemes that our engineers had concocted. Challenging, and quite fun, too! Please don't be offended by this, but in my experience many of the engineers that I have worked with over the years have a tendency to demand perfection, and we don't live in a perfect world...

I have put several engines together over the years and run them in my own cars, and (again) I haven't had a problem with using rods that were discolored from pin installation. I have assembled engines where ALL EIGHT rods showed the discoloration seen in your photo, and put many thousands of miles on them with no problems. In my experience the biggest problem that you are likely to encounter would either be bolt failure or issues stemming from questionable metallurgy, Like so many of the parts that we buy nowadays, Scat rods are Chinese...

Also, after actually reading that page from Eagle, the reference was made specifically to a rod whose bottom end was discolored from having a bearing shell spun around inside it, no doubt at very high rpm. The material condition of that piece has been altered from the inside out, and the heating likely affected the condition of the bolts as well, which are the Achilles' heel of any connecting rod. In your case (and the case with any pressed-pin rod) the upper part of the beam was heated externally to grow the pin bore sufficiently to drop the pin in, which HAS to be done in order to insert said pin. I really don't think that that little article is analagous to what you're seeing here.

If you do choose to return to your machinist with this, PLEASE do not preface your questions with "I'm an engineer..." While I really do respect your education and intelligence, I highly recommend you use a healthy dose of moderation when approaching Bubba at Joe's Automotive Machine. Trust me on this, I've been there...

With all that said, I will still defer to my original contention, which is that your parts are fine; go ahead and run them. that is all

 

There is a very good reason for this. Engineers are held accountable for things when they go FUBAR. People putting them together, not so much (unless it was a clear mistake from assembly). We have bills to pay and mouths to feed too. The people we report to DEMAND perfection. Anything less is not acceptable. Welcome to my world. Wish I had a dollar for every time this topic has kept me awake at night
Your probably right. But do we want to be 80% sure? Or spend $40 and be 100% sure? If I was spending your money and time I'd probably tell you exactly what you told me (just being honest). But since I'm spending my own money and time, 40 bucks sure sounds like cheap insurance...

Why not? I am proud to be who I am. I've been doing it for 23 years (and successfully too!). I have worked hard for it! If someone is offended by my professional title that is their problem not mine! Although I don't normally approach people in that manner...


I do thank you for your input...

 

Well I just called Scat, they said if it got hot enough to change colors, they didn't do something right, and I should be concerned.

 

Yup.

 

I would listen to scat and replace the rod.When parts are heat treated
they are heated to a specific tempature for a specific length of time and quenched with oil or salt baths.Some heat treat specs can also
call for air quenching.My concern with the localized hot spot in your picture would be you may have a hard spot in rod from overheating.
Very hard steel is brittle and will not have any shock resistance.As
an example think about why shear pins are used on brush hogs,snow
blowers etc..Parts are tempered for this very reason and if you want the ultimate in toughness get them cryoed.

 

You have much to learn my son. People are different than machines. They're unpredictable at their very core. They will make it your problem without reason or Spock's logic.

PS- Don't go to a doctor and then tell him what's wrong with you either. Same principal.

People are funny sometimes.

 

I probably won't go back to them period. I would think that a business who had a good reputation and the least bit conscientious about what their customers think about them would recognize when they made a mistake and do what it takes to make it right. Whether or not I am an engineer (or tell them I am an engineer) should have nothing to do with the problem at hand. That is ridiculous to think otherwise. That is how I would run a business. I am the customer, period. Engineer or not...

Update: I've talked to the machine shop today, and it is clear I'm not getting anywhere with them. They defend their work and say "it'll be ok bud, don't worry". I'm gonna go ahead and bite the bullet for another 40 bucks for my own piece of mind and order another rod. Then take it somewhere else to have it pressed together. Probably going to take the crank and have their balance job checked as well since now I've lost confidence that they even did that right.

 

I think you knew this was the right decision from the get-go. If that rod let go, you'd be out more than just a rod, probably the entire engine would be junk. The shop that did the work would certainly would NOT stand up and take responsibility for a new engine. $40 +++ for a rod and attendant work is really the only way to approach this. Much cheaper than the alternative. And now you know of a machine shop to avoid in the future.


Pete

 

I'm amazed by the ignorance in this thread, and yes, I am an engineer.

 

Pick it all up get a few estimates and file small claims
Its fast cheap and easy to diy no hassle.

Too many hacks in this industry takes the fun out of it sometimes

If it was sized right pressing it shouldnt have been an issue. A guess anyway

Have seen some mild rebuilds they have held up Ok in but wouldnt want it in my motor esp if you were goin gto be beating on it. Thats just careless workmanship.