rod bearing not sitting flush at ends

[gteatr6]

This is the only rod that the bearing doesn't sit flush on the ends. Could the rod have been not resized correctly? Seems like everytime I make time to put my motor together, something is wrong.

 

[Mike T]

I would try another bearing from one of the other rods......if it still doesn't fit I would just get a another rod if it were me. Some of my bearings were slightly staggered side to side but all were parallel/flush at the parting lines.

 

[SHADOWII]

It's the details that get you in the end! Have you logged the dimensions of each rod when you rec'd them from the shop? At the least, make a comparison of the rods and bearings incase an error may have been made on the part of the company(?)

 

[gteatr6]

The rods were resized a long time ago. Long story short, I had a rod bearing fail, but not spin. I had another shop check everything out and was told good to go. I even checked. The sizes are all good. Looks like the first guy botched cutting the rod and cap. I'm almost positive this rod is the one that the bearing failed in too. Always something.

 

[turbodave231]

The bearing shells are supposed to stick out slightly out of the rod and cap. It is called bearing crush. When the two halves come together, they press on each other and create a tight fit in the big end housing. This tight fit is what keeps the bearing from spinning in the housing. Main bearings are the same way.

 

[SHADOWII]

The rods were resized a long time ago. Long story short, I had a rod bearing fail, but not spin. I had another shop check everything out and was told good to go. I even checked. The sizes are all good. Looks like the first guy botched cutting the rod and cap. I'm almost positive this rod is the one that the bearing failed in too. Always something.

Sorry to hear that. Have or can you swap that one bearing into another rod to see if it fits the same in a different rod? That would eliminate the rod theory and check for bearing crush after installing it and checking clearance.

 

[gteatr6]

Sorry to hear that. Have or can you swap that one bearing into another rod to see if it fits the same in a different rod? That would eliminate the rod theory and check for bearing crush after installing it and checking clearance.

It's the rod and cap.

 

[gteatr6]

No more worries on this now. Changed the rod out.

 

[gteatr6]

I happened to have a few lying around from my motor that I broke the crank in. The rod was to size too.

 

[howdies86]

Your rod bore was honed off center on that rod. The ID might be correct, but it moves your piston down in the bore. It looks like a good 1/16th", so think about how much it changes your compression on that cylinder! I got a set that was done that way also. A screw up at the machine shop. Probably an inexperienced machinist. Had to scrap a couple rods.


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[SHADOWII]

I happened to have a few lying around from my motor that I broke the crank in. The rod was to size too.

That's good news, gteatr6!

Your rod bore was honed off center on that rod. The ID might be correct, but it moves your piston down in the bore. It looks like a good 1/16th", so think about how much it changes your compression on that cylinder! I got a set that was done that way also. A screw up at the machine shop. Probably an inexperienced machinist. Had to scrap a couple rods.
Now that could spoil a low budget build!

 

[gunzandgearz]

All good answers, you should torque the rods down to spec and mike the big end to see if its in spec, theyre supposed to take just a little off the cap and torque down cap and resize big end to spec.you can also measure rod with dial caliper from top of big end to top of little end and compare to others'

 

[gunzandgearz]

one more thing I forgot to add, in order to get the proper bearing crush you need between .0006 and .0015 of the bearing sticking above the surface of the rod or block. best way to check this that I have found is to push down on bearing to where its flush with surface and use a dial caliper to see how much is stcking up. but remember six ten thousanths on the bearing would double that if measuring from one side. might ask some of the gurus on this site If they have another way of doing it, this is how ive always done it and haven't had any probs.

 

[gteatr6]

one more thing I forgot to add, in order to get the proper bearing crush you need between .0006 and .0015 of the bearing sticking above the surface of the rod or block. best way to check this that I have found is to push down on bearing to where its flush with surface and use a dial caliper to see how much is stcking up. but remember six ten thousanths on the bearing would double that if measuring from one side. might ask some of the gurus on this site If they have another way of doing it, this is how ive always done it and haven't had any probs.

I believe Howdies86 nailed it with their answer. I did check sizing of all the rods with a 3 point bore mic. All were around 2.2475 with bearing installed and torqued. That gives me .0015 clearance. I noticed the bearing sitting as pictured when I was assembling. The only explanation is the rod was resized off center as Howdies86 explained. Makes sense to me. I wasn't going to chance it, so I changed the rod as it was the only one that the bearing stuck out like an 1/8 inch or more.

 

[turbodave231]

A good machine shop will cut both the rod and the cap, reassemble, torque, then hone the rod big end back to the standard size. Even if the shop cut only the cap (short cut method) you wouldn't see a tremendous difference between the cap and rod half.

If the rods were re- bored on a rod boring machine, they could be off that much.

I have a Sunnen Precision AG-300 gauge and a cap gauge, If you send me the rod, I'll measure it and figure out what really happened.

 

[gunzandgearz]

I totally agree with the rod change not worth chance. since the bearing didn't spin my machinest usually tries to treat it like a main bore and only kiss the cap a little so it doesn't shorten rod,like main putting crank closer to cam.but sometimes cant do,should have youre machine shop buy new rod.