Guys:
Some months ago, I had a set of 6.200" h-beam full floating rods made up for a future 250ci inline project. I provided the manufacturer with an OEM rod as a template to be sure all the critical dimensions were correct. In doing so, I got a bit of an education about the inline rods being different in several ways from a "small" SBC rod since I too thought the V8 rod might be OK to use:
First, as CNC-Dude pointed out, the SBC rod's big end is way too narrow at 0.940" when compared to the six at 1.030. Not sure but I suspect too much oil would be lost out the sides to properly suspend the rod bearing. If that's true, bad things would happen in short order.
Second, the SBC rod's "beam" is slightly off-center between the big end (and small end?) when viewing the rod from the side. The inline six rod is precisely centered. Don't know if this would be a problem or not but I'm guessing the GM engineers designed the two rods with this difference for a reason.
Finally, since two rods share a common crank throw on the SBC, there is no chamfer on the connecting rods where the face each other, and there is a chamfer on the outsides to clear the crank pin radius. The six cylinder rod has to be chamfered on both sides. I would imagine failing to provide for clarence on both sides of the rod would result in considerable damage to both the rod and the crank.
My understanding is that failing to orient the SBC rods correctly regarding the crank pin radius and rod chamfers is one of the mistakes folks make when rebuilding small block Chevys that quickly result in a catastrophic failure.
Russ
Last edited by Russ King; 01/17/13 08:50 PM.
