Rods out of round

[Baprace]

That doesn't sound right to me. 6500rpm in a 347 with 10:1. Not likely, imo- I've used Eagle rods in 7500 rpm Subarus (terribly short rod and oil control) that looked great on teardown. That was ten years ago, though.

No detonation on the bearings?
Could you possibly have used a bad batch of fuel?

Eagle had manufactured con rods out of 4130 material, they were supposed to be rebuilder rods BUT they looked like a race rod, according to them they have quit making rods with that material, now they are either 4340 or 5140 < I might be wrong on the 5140 but it's in the 5100 family, they were called Eagle SIR.

[csx7031]

Thanks for all the replies. I'll try to answer the questions asked. Rods were torqued to spec and checked for roundness before assembly. Torque cycled 2 more times at assembly. Side clearances were .016. Rods are 4340 3/8 bolt I beams. I don't want to start a battle with the manufacturer so I won't name them. They are a well known brand that many, including myself, regard as a good rod for the price. I've used their rods (not the exact same rods) in two other builds with no problems. It only made 410 HP, 380 TQ and lost power each pull after the first one. The cam didn't have enough duration, the fuel curve was too rich, and the bearings were being pinched at the parting line. Please keep sharing your ideas with me. Chuck

[midnightbluS10]

Buy American
Tom

Except buying American doesn't guarantee this won't happen.

[mag2555]

Many people will not reuse a bolt once it's cycled up to full stretch more than 4 times.

[user-23911]

Really?


So torque it up once.

Measure out of round BE tunnels.


Torque it up 2nd time.....measure out of round bearings.




Torque it up 3rd time.........assembly.


But the first time you torque it up the tunnels are out of round??????
Always.

So what happens next?



Of course.........new bolts...................lols

[Dave Koehler]

"pinched at the parting line"
Don't think I have ever seen that issue other than what was mentioned by the old superstock rods.
Do the rods measure small at the parting line?

[cgarb]

The superstock racers used to deal with this when they had to use stock rods. They would deliberately hone the rods oval (wider at the the parting line)

What process was used to hone a rod out of round in a specific direction? A shim somewhere? Just curious.

[Jeff Lee]

A big vice

[allencr267]

Using a lot of hammer taps to seat them during assembly to final torquing?

[cgarb]

I can't see a huge vise being used on a superstock engine...lol. I would see maybe a .001 shim between the parting line and hone it .001 o/s then remove the shim. That's how I would attempt it, but I don't have a rod hone.

[af2]

I can't see a huge vise being used on a superstock engine...lol. I would see maybe a .001 shim between the parting line and hone it .001 o/s then remove the shim. That's how I would attempt it, but I don't have a rod hone.

That is exactly how to do it. Except for the .001 o/s. You have already done it.

[Dave Koehler]

Think C Clamp instead of vise.

[user-612937456]

Isnt the stress that stretches the big end on the down stroke before compression upstroke? This should be a fraction of the load of the other 3 modes. Wht no distortion on other part of the conn rod? My statement may not be relevant but was part of my thought process. Even if the Metallurgy on the rod is soft if it doesn't have the room to distort would it be likely to distort less. As in decreasing the bearing Journal clearance and supplying a higher volume of a much better quality oil to sustain a sufficient oil film Sonic does anybody see where I'm going with that?

I also can imagine the connecting rod Bolt contributing to the Distortion of the connecting rod when it's initially torque down

[Jeff Lee]

Think C Clamp instead of vise.

OK....your right. Been awhile since this was done on my factory forged AMC rods in Stock Eliminator. It added a great deal of life to the rod bearings but not near enough. Allowance of aftermarket rods was best thing that happened to Stock. Or worst. Depends on what side of the fence your on with rule revisions.
I went to Manly and Oliver Rods and have had no problems since. Even in SuperStock.

[MadBill]

Isnt the stress that stretches the big end on the down stroke before compression upstroke? This should be a fraction of the load of the other 3 modes. Wht no distortion on other part of the conn rod? My statement may not be relevant but was part of my thought process. Even if the Metallurgy on the rod is soft if it doesn't have the room to distort would it be likely to distort less. As in decreasing the bearing Journal clearance and supplying a higher volume of a much better quality oil to sustain a sufficient oil film Sonic does anybody see where I'm going with that?

I also can imagine the connecting rod Bolt contributing to the Distortion of the connecting rod when it's initially torque down

The heaviest tensile ('ovalizing') rod load is in the vicinity of TDC on the exhaust stroke, where there is usually little or no gas pressure (hopefully even negative pressure) to offset the force required to slow/reverse the piston motion.
It's not possible to maintain the rod shape via support from the journal; the distortion would just cut through the hydrodynamic wedge of lubrication, causing instant meltdown of the bearing. The forces within the wedge are in the thousands of psi and can't be remotely affected by pump pressure; pressure is just a major factor in the volume flow and cooling capability.