[Jay S]

Originally Posted by unruhjonny

thanks!

to bring this back to the discussion of “rubber rods” (a new term for me!) vs earlier SD rods vs 58-62 rods…
it looks like the older stuff all the info is there;

1) what info is there to compare the (66+?)69-78 rods against the earlier ones?

2) so what might stop a person running an earlier engine with the later cast rods?

The connecting rods sometimes referred to as the rubber rods are made from 58-62. Next came the Nodular Arma steel rods 63-67 (may have went into 68) rods which had a slightly lighter I beam versus the 68 and up nodular rods. The rods from 68 and later are all close to the same except the 73-78 eliminated the lube hole in the cap to spray toward the cam. New rod bearings do not have provisions for the oiling anyway, so that is no big loss.

You can switch any of the rods around, it just affects the balancing. The rotating assembly ends up a couple percent off. Most of the extra weight on the nodular rods is at the piston end, so most of the difference in weight is cut in half on the bob weight. In other words the extra weight of the nodular rods is more on the piston end, which often times mean you can swap the rods back and forth a not notice as much difference in balancing a you might expect.