JNVA17

So I polished my pistons and rods at my job and I forgot about the little numbers that match the rod bearing cap to rod. They're all blank now. My machine shop yelled at me because I brought some in with the caps mixed up. They told me it was bad news. Is there a way to match the rods and caps without the number??

ezone

You got 8 chances to get them all wrong.
If the rods are fractured caps, they are easier to match up. If they are all machined flat, that's harder.


Rods and their caps are machined while bolted together under full torque as a unit and become a matched set .

Hopefully there is at least one matchmark on each rod and cap from the factory.
If not, all you can do is trial and error and hope you don't ruin them before you figure it out.

If you get a rod cap turned backwards, it will probably cause the whole thing to not be able to spin on the crank.




Pick one rod and one cap.
Insert the bearings.
Stick it on the crank, assemble with only your fingers, no nuts.
Can you squeeze the rod cap flat against the rod?
Will it spin free?
If no, then turn the cap around and retry.
No? Try another rod cap.
Keep doing this until you have a set that will spin free.
Mark them with a sharpie and set them aside.

Repeat for all 4 rods.

Once you THINK you have all 4 matched, now you try it all again with the nuts installed, finger tight. If they all still spin free, then torque the nuts.
If any don't spin freely at any point, stop and back up. Try another rod cap. You have at least 7 chances of being wrong for each of the 4 rods.
If you STILL have them all free spinning, then you probably won this round.
Punchmark them all permanently.
Have an adult beverage.
Hope it lives once you fire it off.

HTH

KyleSJ6033

So you polished each why? If anything you should be filing them to all the same weight for a more balanced motor. But each cap will have lock tabs for the bearings to sit in. the rod itself will have one and the cap will have another in a different spot. These actually hold the bearing in place so they dont spin around. These are important to get right tho. The only fix without trial and error is to get them all machined back to alignment. Even then there is a possibility that one of them gets over machined. The rods wear a specific way on the crankshaft. Same as the rods sit a certain way in the cylinder wall. I am willing to send you a set of y7 rods if that helps you any. I think they are the same length. I will be taking them out of my car this week either way. Im putting H beam rods in mine and the factory ones are not damaged. The only reason Im replacing them is Im putting the others in so I can crank up my boost some more. I will also have the factory pistons on them which are 75mm.