Connecting rod concerns?

[steve murdoch icoa #5322]

Found some of the answers i needed but this is new to me.

I understand there are A, B, C, D rods. The letters and numbers being stamped on the side.
Are there also #1, #2, and #3 of each letter?

I understand it is best to have the same letter rods in each engine.
Is it imperative? Is this because of weight or does it have to do with bearings/journals?
Can all letters be used in each year engine?

What are these other markings cast on the side and bottom of the rods about?

[daves79x]

The weight code is extremely important. The shop manual lists in detail what weight code rods can go together, but I like to use all the same letter. I double-check each one by weighing them. There is a lot of difference in weight between the letter codes. The numbers are the journal size and what you use, along with the crank journal code, to determine what size (color) bearings to use. The other markings you show mean nothing.

Dave

[steve murdoch icoa #5322]

Thanks for that info, Dave.
I had seen the chart in the manual but didn't have it sorted out.

A guy local to me called looking for a D3 rod. The only spares i have are B.
In a previous post i read you said to replace the one removed with the same code.
He actually hydro-locked #4 on '82. I had only heard of #1 blowing up on the early '79s. I should have taken a photo of the rod.
The piston had only some very light scuffing on the inside of the skirt.