Power Limit of RB26 Rods?

[DoughBoy]

The HKS rod is for an RB26, the bent rod is out of an SR20, the rod with the piston on it is from an RB26 - tore down the motor over the weekend.

The few RB25 rods that I have seen break at the 'neck' area just where it contours down to the beam of the rod - high revs being the cause.

[Sydneykid]

Hi guys, time to get out the verniers and measure them up. That'll settle it once and for all.

[DoughBoy]

Uh ok.. well I got out the measuring tape... you sure you don't want to go first Sydneykid?

[Parag0n]

Hahaha, Doughboy has a dirty mind

[B-Man]

I'd like to know the answer to this - hmmm very interesting....

[GTRgeoff]

It's clear these are two different rods, and unfortunately it confirms mine are the inferior R25 rods.

Some notes on the visual differences and the structural implications. Areas are marked A and B.

At area A the 26 rod (the unmarked image) has a much beefier lug area around the head of the bolt, which gives greater support to the most significant difference at Area B, where the 26 rod starts to taper out toward the rod bolt much higher up the rod length. This is significant because the inertial mass further away from the crank adds up and can cause permanent deformation or complete failure so has been countered by adding more and more material further away from the piston. So instead of more mass all along the rod, it has been added little by little where it is needed most. If a constant size rod were to snap due to inertia from mass toward the free end, it would obviously snap toward the constrained end.

In addition the tapering gives significant columnar stability due to compressive forces.

All of this adds up making this rod far more capable in terms of high power and high rpm application...DAMMIT!!!