Eagle H-Beam Connecting Rods (Set of 4) for 90-97/99-04 Mazda Miata
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All Eagle H-beam rods are forged from certified 4340 chromoly steel. While a lot of companies make rods from this material, if you pay close attention, you will notice not all 4340 is the same. For instance, to be classified as "4340 steel" certain alloying elements must be present in certain percentages. AISI/SAE specifications call for 1.65% to 2.00% nickel content. While this seems like a small difference, understand that this is almost an 18% variation. 4340 steel with 1.65% nickel will act a little differently than 4340 steel with 2.00% nickel content. This is just one of many alloying elements involved in creating 4340 steel. Through extensive material testing, Eagle works closely with their foundry to achieve a much tighter tolerance of all alloying elements to their specific requirements. Along with this, the heat treatment and tempering process used is vital to producing a strong steel. While exactly what Eagle does is a closely guarded secret, all of this attention to detail results in a stronger and much more consistent material. Eagle's "4340" steel routinely tests 10-15% stronger than "typical" SAE/AISI spec 4340 steel.

Another important design feature is all Eagle H-beam rods are manufactured from a 2 piece forging. This is significant because it enhances the strength of the rod cap by orienting the "grain" of the metal with the direction of stress. The stress exerted on the cap is perpendicular to the stress on the beam. Forged metal, like wood, has a grain "flow". While wood is stronger in compression and tension when the stress is applied along the grain, it is weaker when the stress is applied perpendicular to the grain. The same is true for steel. Although not as severely different as wood, forged steel will show the same type of result. It might be minor, but several "minor" enhancements combined together result in a major improvement. Eagle also never uses "cracked cap" type of manufacturing. This is a cheap alternative to try and produce a more perfect fit between the cap and the beam. The problem is that in order for this to work, the rod material must be brittle (that's bad), and Eagle would have to make the rod as a single forging. Instead of resorting to those kind of measures to achieve a "perfect" fit - Eagle just machines the rod and cap perfectly. So much so that it is difficult to see the parting line at all! Eagle uses the state-of-the-art Sunnen Krossgrinding system to achieve perfect bore size and consistency unmatched in the industry. This system is completely computer controlled and produces perfect and repeatable results every time.

Standard Forged 4340 Steel H-Beam

Fasteners: 3/8" ARP 2000
Torque: 43 ftlbs with ARP moly lube on threads
Pin Fit: bushed
Recommended up to 900 HP

DIMENSIONS
Length: 5.233 in.
Rod Journal: 1.770 in.
Housing Bore: 1.8900 in.
Pin Size: 0.787 in.
Big End Width: 0.8580 in.
Pin End Width: 0.8580 in.
Thickness Above Pin: 0.180 lbs.
Typical Weight: 535g

Recommended Bearings: CB1453AL

NOTES:
1.6L and 1.8L "B6", "BP" engines

Identifying Marks:
CRS-5233-M