Standards
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Connecting Rod Bolts
Connecting rod bolts clamp the rod cap to the rod beam and take peak tensile load at the bottom of the firing stroke when the piston decelerates. They are the highest-stress fastener in any reciprocating engine and are widely upgraded in race builds, drag and circle-track engines, and forced-induction rebuilds because the stock OE rod bolts are sized for OE redline and OE compression ratio, not for boosted, high-RPM, or nitrous-fed operation. The 12-point head is the standard drive geometry on rod bolts because the rod-beam pocket is shallow and the twelve splines allow the very high torque-to-yield or torque-plus-angle preload procedures that race-rod bolts require.
TorqBolt manufactures connecting rod bolts in L19 race-grade alloy steel (270 ksi for top-end race), AISI 8740 chromoly heat-treated (220 ksi for heavy-duty builds), Custom 465 (260 ksi corrosion-resistant), 17-4 PH H1025 and AISI 4340 to AS9100D Rev D and ISO 9001:2015 quality systems. Each bolt head carries the struck tB manufacturer ligature plus the alloy grade marking, and every lot ships with a mill test report (MTC 3.1 standard, MTC 3.2 critical with hardness, tensile, magnetic-particle and shot-peen-after-thread-roll process inspection records).
Materials
Alloy choice is set by the spec, the service temperature, the corrosion environment, and the strength target. TorqBolt routinely produces connecting rod bolts in A286 (UNS S66286), Inconel 718, Ti-6Al-4V (Grade 5), MP35N (UNS R30035), Custom 465 stainless, AISI 8740 chromoly heat-treated, AISI 4340, 17-4 PH H1025 condition, H-11 tool steel, and L19 race-grade alloy steel.
Race-engine rod bolt context
Connecting rod bolts retain the rod cap to the rod beam at the crank journal, transmitting tension and shear under the alternating compression-tension cycle of every engine revolution. Stretch and re-torque are not optional in race-engine builds; the rod bolt is THE most stressed fastener in the bottom end. Common alloys: L19 race-grade alloy steel at 270 ksi for top-end drag and circle-track engines, MP35N at 260 ksi for high-RPM road race and rally where corrosion exposure (oil + heat + moisture) matters, and heat-treated AISI 8740 chromoly at 200 ksi for street builds where budget rules.
Companion bolts in the same engine build: main cap bolts and main studs retain the crank in the block, head studs retain the cylinder head against combustion pressure, flywheel bolts retain the flywheel against rotational mass, cam bolts retain the camshaft against valvetrain shock. All five typically share the 12-point geometry on race-engine builds for the same wrench-engagement reason. Quality systems documentation: see About TorqBolt QA-QC. For a deeper view of UNJ-3A external thread dimensions common across these bolts, see the dimensional table.
Request a Quote
RFQ to info@torqbolt.com, call +91-22-66157017, or WhatsApp +91-22-66157017. Mill test report (MTC 3.1 standard, 3.2 critical-service) ships with every lot.
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