Mystery--Shims on V6 rods???

In cleaning up my V6 rods and pistons I found #3 and 4 had a .001 brass shim under the rod bearing on the cap side. What the heck---first time the engine has been torn down, everything is standard in size. Did the factory do this?? Should I put the shim back in? Help

 

I would say that yes no matter what you think, the motor has been torn down. That is a fix I have seen old timers do on tractor motors and such. There is no way that the factory did this as they only have tools on hand to do the job they are assigned and having shim stock lay around for that would be a big no no.

 

Yeah, it's an old-time fix. Andy Granatelli (in his book) talks about shimming rods when he worked in a shop in the 30s or 40s - that's the only place I've heard of it. I agree with Mike - nobody would do that in a modern factory setting.

 

the shim is to tighten up a loose bearing . you only use a shim or you could also sand the cap to tighten it too. just a few thousand of inch. on the cap you first remove the bolts and place on a flat table to hone it by using wet or dry sandpaper.

 

Thanks guys!! A little more info---the shim stock does not look like it was cut by hand, very stright and square cuts just like it was made for it. Usually, you don't see that quality of work comeing out of someones back yard. If it was done in a machine shop---the question is then WHY when all they had to do is mill the ends of the cap. I mic the shim and its .001 of an inch. The bearings didn't have any funny wear patterns. If I take a little off the cap, it would seem that it wouldn't take much to shave off 1/1000 of an inch.

So, if I understand this correctly----the bearing insert without the shim will have .001 too much gap between the two bearings when bolted together. By placing the shim in place, it brings the bearing up tight agaist the other bearing--which in turn, provides the correct tolerance on the crank.

 

This was a common practice amongst shade-tree mechs (40's-50's) when we used babbit inserts. You placed the shim in the cap, inserted babbit, held tight with fingers and trimmed shim stock with exacto knife. Wala perfect cut. Looked factory. We would also grind down caps using valve grinding compound on glass and rotate cap in a figure eight lapping and over lapping to get both ends equal. Worked very good. It is time consuming but what the heck, back then we had plenty of time..