Rod Bearing Misalignment

['76 911S 3.0]

I'm in the process of putting my engine back (3.0 ltr) together and noticed an issue with the rod bearing alignment between the cap and the rod. For reference, these are GT3 STD Rod Bearings. I have installed the bearings that were originally in the engine and they align the in the same manner as these. Is there something I am missing here?

The rods have been resized and balanced with ARP rod bolts installed...





TIA for any insight.

-Jayson

[jpnovak]

Is the cap on backwards?

[T77911S]

flip the cap so the tabs are on opposite sides

['76 911S 3.0]

Cap is installed with the numbers on the same side as they were when they were removed from the engine but I'll triple check to make sure I put them together properly.

['76 911S 3.0]

Flipping the cap so that the tabs are on the opposite sides gets the bearings to line up perfectly. However, the thrust surface of the rod is misaligned and the numbers are now on opposing sides of the rod.

[john walker's workshop]

never put any bearing tabs on opposite sides!

['76 911S 3.0]

Originally Posted by john walker's workshop

never put any bearing tabs on opposite sides!

Agreed! I'm just dumbfounded to the fitment of these bearings, especially since the original bearings fit the same way!

[Hil911]

Agreed - looks weird!

How wide is the crank pin onto which they must fit? The edges of those bearings have to centre the big end. If the bearings are too narrow when aligned but fit when they are stepped, as you show, then presumably the offset is correct! It wouldn't be right to have lateral play, I think.

Or am I misinterpreting where the thrust edges are?

['76 911S 3.0]

I just confirmed with the engine builder at 911 Design in Monteclaire, CA that these bearings do in fact sit with an offset in the rods in the earlier engines. For whatever reason, Porsche designed these rod bearings to fit in such a manner and he told me there is no cause for concern.

Hil911, the thrust edges I was referring to are on the physical sides of the rods. When the caps are installed incorrectly, the thrust edges do not align and create an offset where only one side of the rod (either the cap or the rod) would ride on the thrust surface rather than the entire big end.

Hope this acts as a reference to anyone building their engine in the future!