Reading Connecting rod bearings

Checked connecting rod bearings last night and noticed at the edges of the bearings it appears the crank is not wearing on the bearing (approx 3/8”). No shinny spots as seen on the rest of the bearing. Bearings checked good. Rods have 11 runs on them. These are Brooks 88 rods in a 526 blown Hemi. Is this normal? Rods out of round?
TX's for any help.

 

Use a set of calipers and measure the width of the top of the bearing compared to the width of the middle. The difference in measurement equates to how much bearing smash you have. We change ours at .005. Anything less than that we just clean up the edges of the bearing and put them back in.

 

Thanks Blwnaway,

That's the way I check the bearings. 11 passes and there at .001. Had a little push out on #4 & 6. Just cleaned it up. The last set of bearings I replaced at .003 and do not remember if I had this non-shinny spot.

TX's again

 

Bearings

Are you referring to the ends of the bearings next to the parting line? If so sometimes mine don't seem to wear there either. I haven't ever bothered to measure them but it is almost like they are tapered towards the ends and because of that they don't wear there. If you find out what the issue is please let me know too. Dave Germain

 

You may have answered the question. The rods will go out of round depending on how hard you are running the engine. How many runs on the rods? I use to resize this brand of rod at 8-10 runs with a PSI. Then cycle them at ??what you feel comfortable with. Replaced ours at 23 runs.

 

Rod bearings aren't "round". They are built with more side clearance, at the parting line, then vertical clearance. The reason is forces that are put in the center of the bearing from the top of the rod under compression, and on the cap when the piston changes direction, squeeze the rod itself in at the parting line. If you imagine a "c", pushing in the the middle of it would make the top and bottom close down. A rod does the same thing. The amount horizontal clearance vs vertical clearance will vary depending on the bearing itself. In the "old" days, you would have to resize the big end of a rod on a "true" race engine with a c-clamp on the parting line of the rods, so you could increase the horizontal bearing clearance enough to keep the poor old bending rods from letting the bearing grab the crank.
shawn

 

question for Shawn

Thanks for the explanation. It certainly makes sense but it also raises another question. If my bearings aren't wearing along the parting edges does that mean I am not running the car hard enough? Dave Germain

 

No, they just dont wear there because the rod has no bearing stress side to side.