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-   -   Question on undersized rods (https://www.onlycubcadets.net/forum/showthread.php?t=34179)

bocephus1991 08-22-2014 06:32 PM

Question on undersized rods
 
Took. My engine to the machine shop after work told what I wanted done and will have to wait a week till the get back to me with measurements , anyways I was told if it needed a .20 under rod it would need a bearing installed. I thought a .20 under rod didn't have bearing?

cubs-n-bxrs 08-22-2014 06:47 PM

You can get a .020 under rod through Kustom Lawn and Garden. BTDT:beerchug: Extremely fast shipping. Ordered one day received rod 2 days later.

J-Mech 08-22-2014 07:07 PM

I'm going to start doing bearing inserts on all my rods. That way, they are re-usable. You can go with a .020" under if you want. My machine shop will machine the rod and install the bearing for the same price or just a little less, than a new rod. Your choice.

bocephus1991 08-22-2014 07:56 PM

I don't know what size I need as of yet. I just thought a .20 under rod was made like a standard size just larger to accommodate the turning of the crank from machining . From way it looked could be within spec, both rod and crank look fine. Oh he also advised against reusing the old rod even if good on specs . He sad he would worry about fatigue of the rod.

J-Mech 08-22-2014 07:59 PM

Quote:

Originally Posted by bocephus1991 (Post 282327)
......I just thought a .20 under rod was made like a standard size just larger to accommodate the turning of the crank from machining . ......

That is correct.

I've not seen very many cranks that were "withing spec" enough that they didn't need turned. Expect at least a .010" under.

Jeff in Pa 08-22-2014 09:05 PM

Quote:

Originally Posted by bocephus1991 (Post 282327)
I don't know what size I need as of yet. I just thought a .20 under rod was made like a standard size just larger to accommodate the turning of the crank from machining . From way it looked could be within spec, both rod and crank look fine. Oh he also advised against reusing the old rod even if good on specs . He sad he would worry about fatigue of the rod.


Please excuse the machinist ( :biggrin2: ) as he nitpicks your post.

When the crankshaft rod journal is turned .020 undersized, it will require a connecting rod with a smaller hole size to have the correct clearance.

~~~~~~~~~~~

He is correct on the rod, aluminum fatigues with use and it will fail at some point.

bocephus1991 08-22-2014 09:11 PM

That's what I was thinking too .10" under. The place was busy several 6 cylinder blocks a 3 cylinder jd block , quite a few diesel heads. It is a new building, their old one burned last fall they lost all their machines several engines. Thanks Jonathan for confirming what I thought about the rod . That's ok Jeff no problem with nit pickin !

dvogtvpe 08-22-2014 09:18 PM

Quote:

Originally Posted by J-Mech (Post 282320)
I'm going to start doing bearing inserts on all my rods. That way, they are re-usable. You can go with a .020" under if you want. My machine shop will machine the rod and install the bearing for the same price or just a little less, than a new rod. Your choice.

I thought of doing that at one time but I came to the conclusion that just using a new rod was better. I really don't trust boring a used rods unless it the K361 rod

J-Mech 08-22-2014 10:57 PM

Quote:

Originally Posted by dvogtvpe (Post 282343)
I thought of doing that at one time but I came to the conclusion that just using a new rod was better. I really don't trust boring a used rods unless it the K361 rod

Afraid of rod fatigue? Dean (my machinist) and I discussed rod fatigue. We didn't think it would be an issue, but weren't sure. :bigthink:

Do you run any of your motors with bearing inserts? What about boring a new rod?

I may still try it on some of my own (just because). I've got a few good looking Kohler rods that I wouldn't re-install just because they are used, but they aren't "spun".

dvogtvpe 08-22-2014 11:30 PM

Quote:

Originally Posted by J-Mech (Post 282359)
Afraid of rod fatigue? Dean (my machinist) and I discussed rod fatigue. We didn't think it would be an issue, but weren't sure. :bigthink:

Do you run any of your motors with bearing inserts? What about boring a new rod?

yep, its a bad rod to start with. I wouldn't be afraid to insert a new one. I stopped doing inserts when I could no longer get or find the K361 rod. the last few stocker pullers I did ,I put a stock length aftermarket rod in. you do need to rebalance the rotating assembly


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