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Old 07-21-2013, 02:39 PM
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no play connecting rod 1 side only

Hey fellow powerhungry maniacs!
I am putting together the bottom end of my small block chevy and have an issue I hope someone may have knowledge on.
It is a .060 over balanced eagle rotating assembly.
One of the two connecting rods in one rod journal has no side to side (meaning it can't move side to side, but can be rotated with crank) when bolted down to spec. The one next to it can.
Rod bearing measures the stock .063" thickness and is 2.16" inside diameter of the hole.
Bought more bearings thinking one might be thinner, but I'll be damned, eagle is perfectly consistent with those measurements.
So: Bad bearing edge chamfer?
Bad piston rod big end hole diameter?
Something else out of whack?
Or am I ok?
Any help much appreciated.
Will update with my progress.
Thank you all.

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Old 07-21-2013, 04:31 PM
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Quote:
Originally Posted by Woodsman View Post
Hey fellow powerhungry maniacs!
I am putting together the bottom end of my small block chevy and have an issue I hope someone may have knowledge on.
It is a .060 over balanced eagle rotating assembly.
One of the two connecting rods in one rod journal has no side to side (meaning it can't move side to side, but can be rotated with crank) when bolted down to spec. The one next to it can.
Rod bearing measures the stock .063" thickness and is 2.16" inside diameter of the hole.
Bought more bearings thinking one might be thinner, but I'll be damned, eagle is perfectly consistent with those measurements.
So: Bad bearing edge chamfer?
Bad piston rod big end hole diameter?
Something else out of whack?
Or am I ok?
Any help much appreciated.
Will update with my progress.
Thank you all.
Are you sure the bearing shell isn't running into the chamfer on the crank? Narrowed bearings are available or can be made to fit if that's the problem. Be sure the rods are in the correct orientation. If you're going by the piston notch to the front (or whatever it may have to show front), the piston could be on a rod backwards, so be sure they're right.

If not, you might have an unusually wide set of rods paired on that journal. Sometimes swapping rods around will bring the side clearances into spec. But you have to have side clearance, else the rods will quickly overheat and take out the rods, bearings and crank with them.
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Old 07-21-2013, 04:49 PM
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Thanks cobalt!
Yeah, I'm wondering about the bearing being too wide.
With the fact that the other rod on the journal has movement and clearance, even with this one torqued,
I figure the bearing is either too fat or too wide and clamping too tight or hitting that journal radius. Don't know how I'd physically check for radius/bearing edge clearance, but I I'll just have to try some other bearings and see whats what.
I do, however, know that the end is correctly clamped and situated.
Engine building seems to be like a game of operation. The red light keeps coming on.
Thanks so much for the reply!
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Old 07-21-2013, 04:58 PM
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Don't take this the wrong way but is the rod on the piston the correct way?
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Old 07-21-2013, 05:06 PM
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The piston wrist pin could also be installed incorrectly. If it hits the piston pin bore boss, and not allow enough travel for the rod to move to float on the crank journal........
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Old 07-21-2013, 05:25 PM
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Thanks guys,
No insult taken, man I'm lax as they come, but yes the rod is on correctly.
Chamfer twords crank.
Meanwhile, the small end is floating freely. It was put together by eagle. Never the less, I did think to check that it could move on the pin back and forth freely before fully torquing the cap down.
I just measured the bearing that came off
Bearing that came off: .837" wide and .064"thick
All of my freshly bought brandy new bearings measure the same.
I see no notable wear on the edge of the bearing set I took out that would, to me, indicate a bearing to radius mismatch. It had been rotated a good few times, so I'm now pretty sure its not the bearing to blame.
Perhaps I actually got an out of round rod from eagle?
I dont yet know.
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Old 07-21-2013, 08:38 PM
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Measure all the big end rod widths. Then measur the cheek to cheek width of all the rod journals. See which one is different.
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Old 07-21-2013, 09:38 PM
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Nice one. I will try this and post results. Thanks.
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Old 07-22-2013, 05:21 AM
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Is the mating rod hung correctly? Chamfer towards the crank.
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Old 07-22-2013, 05:16 PM
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Ok everyone, thanks for the suggestions.
Small end of rod in question, and all other rods have ample side to side play bolted down or not. So it isn't a pin play issue.
Tried a new bearing on rod in question, but it seized up (no end play) and could not move side to side just as before. Other rod on that journal moves when clamped, just not much. So not the bearing.
Measured the rod thicknesses at .937" and .939" equaling: 1.876" for both totaled.
The measurement of the rod journal was 1.901"
1.901" jounal minus 1.876" for two rod ends equals .025" end play.
Keep in mind .025" end play may be excessive, but my readings could be off by as much as .005" and we are considering why one rod cannot freely slide side to side, so who cares about excessive end play in this situation right now.
I called a builder, he suggested taking off the non problematic rod and then torquing down the problematic one and seeing if it would budge stand alone.
It did not. It was stuck in place and would not slide side to side regardless of repositioning inwards more to center of journal.

In summation:
Not a bearing problem
Not a small end problem
Not a chamfer to journal problem or incorrect rod install problem
Not a side clearance problem.
Seemingly not a journal problem as they all measured good previous to assembly

Whaaaaa?
It is a rotating balanced assembly from eagle.
Guess I'll call summit (purchase of origin) or eagle to figure out next step?
I wouldn't want to try another rod/piston assembly in its place. What if then it possibly hurt another rod?
I think I'd rather they tell me to do that than I take that blame myself.
What do you all think?
As always, I thank you in advance for any feedback you might be so inclined to muster.
- The Woodsman -
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Old 07-22-2013, 05:55 PM
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OK Take the other rod and piston out. Loosen the rod bolts in question, NOW you should be able to slide the rod over. If not you have rod end out of round or something stopping that rod from moving. You have bearing / Cap mismatch or something really simple. Can you turn motor over with that rod torqued down?
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Old 07-22-2013, 05:59 PM
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I think you answered your own question. Check the big ends for roundness. If found to be out of round or miss sized would make Summitt take the whole assy back.
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Old 07-22-2013, 09:45 PM
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Either end could have the hole machined off center as shown by the red lines, or the rod could be warped in the orientation shown beside the rod in red below:

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Old 07-23-2013, 12:24 AM
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Ok, thanks guys.
So as I stated, the rod in question will not budge stand alone by hand when torqued to spec. Tapping with a rubber mallet moved it, but I naturally don't want to have to do that (and risk injuring the crank), and the engine will rotate by hand relatively smoothly (some slight resistance in spots) when torqued. The rod plays fine when not torqued to spec. Alone, the other side will too, by hand, torqued to spec or not, but almost none with the question rod torqued to spec.

I am unaware of the procedure for measuring out of roundness, but perhaps I should just grab another rod from summit or eagle and get it installed to my piston? This would be a relatively cheap and quick solution if I am rather certain the rod is out of round anyway. I would re-measure the journal with my digital vernier caliper before doing so to be quite sure it is indeed in spec first.

This is a street engine. I want to build it as right as possible. I am surrounded by "knowledgeable" people all day telling me to "just run it" and such alike, but I find we differ in opinion on this matter. I truly don't feel this is a place to sleep.
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Old 07-23-2013, 12:51 AM
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Quote:
Originally Posted by Woodsman View Post
Ok, thanks guys.
So as I stated, the rod in question will not budge stand alone by hand when torqued to spec. Tapping with a rubber mallet moved it, but I naturally don't want to have to do that (and risk injuring the crank), and the engine will rotate by hand relatively smoothly (some slight resistance in spots) when torqued. The rod plays fine when not torqued to spec. Alone, the other side will too, by hand, torqued to spec or not, but almost none with the question rod torqued to spec.

I am unaware of the procedure for measuring out of roundness, but perhaps I should just grab another rod from summit or eagle and get it installed to my piston? This would be a relatively cheap and quick solution if I am rather certain the rod is out of round anyway. I would re-measure the journal with my digital vernier caliper before doing so to be quite sure it is indeed in spec first.

This is a street engine. I want to build it as right as possible. I am surrounded by "knowledgeable" people all day telling me to "just run it" and such alike, but I find we differ in opinion on this matter. I truly don't feel this is a place to sleep.
Instead of buying another rod that you might not need, take the suspect rod to a machine shop to be measured if you lack the tools to do this yourself. BTW, have you tried swapping bearings from another rod yet?

But you can measure for the rod being out of round if you take your time using a telescoping inside gauge (shown below) and a caliper. Even plastigage will show you whether there's an out of round condition, it just won't tell you if it's the rod or crank journal. Take a measurement w/the plastigage, then rotate the crank 90 degrees and take another, etc. until you've gone around the crank journal. You can eliminate or confirm the crank journal as the problem by temporarily replacing the rods from another journal on the suspect journal. If these different rods are OK, suspect the rod as being the culprit.

Plastigage can also show if the rod's warped or the big end isn't centered. If it's warped, the plastigage will be wide on one side and narrow on the other. This assumes the journal has been verified as being OK by the method above or by using a micrometer or even a good caliper.


Last edited by cobalt327; 07-23-2013 at 01:02 AM.
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