Engine Specs - S65/S85 Rod Bolts

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Which rod bolts are best?

A lot of people ask which connecting rod bolts are best, and which they should use.  There is no simple answer.  Factory bolts cost less but take longer to install.  Once you use them, you need to throw them away and buy new ones.  Aftermarket bolts cost significantly more (3x, 4x) than factory bolts, but they take less time to install and can be reused.

While there is no doubt aftermarket rod bolts will be higher quality and stronger than factory bolts, they also have some side-effects that most people don't realize.

Clamping force

The ability to keep the rod bore perfectly round will depend on the clamping strength of the rod bolt itself.  Believe it or not, all rod bolts when torqued to specifications do not have the same clamping force.  To keep the rod bore round will depend on keeping the rod bolts at the same clamping force.  You can assume the factory rod bolts when torqued to factory specifications will do the job correctly.  But the same can't be said for the aftermarket rod bolts as we shall see below.

Rod bore distortion

When the rod bore gets deformed, we call this rod bore distortion.  This is measured with a bore gauge at multple angles around the bore.  From these measurements we can compare the differences and create a map of the bore distortion, if any.

Factory rod bolts

Specifications: Torque procedure

Torque Angle
20 Nm 130 degrees
Remove  
20 Nm 130 degrees
Remove  
20 Nm 130 degrees


Make sure you are starting with new rod bolts.  Factory rod bolts must be replaced once used.

  1. Lubricate rod bolt threads and connecting rod cap bore holes with appropriate thread lubricant.
  2. Torque to 20-Nm, then using a torque-angle gauge tighten another 130-degrees.
  3. Remove bolts.
  4. Repeat steps 1-3
  5. Repeat steps 1, 2.

Specifications: Clamping force

  • Approximately 11000 pounds force.

Specifications: Measurements

Angle R1 R2 R3 R4 R5 R6 R7 R8
5.00 2.20495 2.20500 2.20510 2.20510 2.20500 2.20510 2.20495 2.20500
19.75 2.20500 2.20490 2.20500 2.20510 2.20500 2.20510 2.20480 2.20500
45.00 2.20500 2.20480 2.20500 2.20495 2.20500 2.20490 2.20480 2.20490
90.00 2.20520 2.20480 2.20500 2.20480 2.20520 2.20490 2.20480 2.20500
135.00 2.20520 2.20490 2.20500 2.20480 2.20510 2.20500 2.20490 2.20490
160.25 2.20510 2.20490 2.20500 2.20500 2.20510 2.20500 2.20490 2.20500
175.00 2.20500 2.20500 2.20500 2.20500 2.20500 2.20500 2.20480 2.20500

Specifications: Rod bore distortion

Measurement Angle R1 R2 R3 R4 R5 R6 R7 R8
5.00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
19.75 0.00035 0.00020 0.00027 0.00033 0.00027 0.00035 0.00040 0.00022
45.00 0.00090 0.00038 0.00062 0.00088 0.00060 0.00067 0.00072 0.00050
90.00 0.00120 0.00060 0.00087 0.00108 0.00095 0.00097 0.00102 0.00073
135.00 0.00090 0.00038 0.00062 0.00088 0.00060 0.00067 0.00072 0.00050
160.25 0.00035 0.00020 0.00027 0.00033 0.00027 0.00035 0.00040 0.00022
175.00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000


OEM-Rod-Bolt-Eccentricity.jpg

ARP-2000 rod bolts

ARP-2000 rod bolts are a step up in strength and quality from OEM factory bolts. These bolts for S65/S85 are custom made by ARP for VAC Motorsports. ARP does not manufacture and sell these bolts to the public. You can only get these through VAC Motorports.

Specifications: Torque Procedure

  • 45 ft-lbs.
  • Unlike the factory rod bolts, these may be reused.

Specifications: Clamping force

  • Approximately 8150 pounds force.

Specifications: Measurements

Measurement Angle R1 R2 R3 R4 R5 R6 R7 R8
5.00 2.20480 2.20480 2.20480 2.20475 2.20480 2.20475 2.20475 2.20485
19.75 2.20510 2.20500 2.20510 2.20510 2.20520 2.20515 2.20515 2.20500
45.00 2.20560 2.20515 2.20540 2.20560 2.20540 2.20545 2.20545 2.20530
90.00 2.20600 2.20540 2.20565 2.20580 2.20575 2.20575 2.20580 2.20560
135.00 2.20580 2.20520 2.20540 2.20560 2.20540 2.20545 2.20555 2.20545
160.25 2.20520 2.20500 2.20500 2.20500 2.20495 2.20510 2.20520 2.20520
175.00 2.20480 2.20480 2.20475 2.20470 2.20480 2.20480 2.20480 2.20490

Specifications: Rod bore distortion

Measurement Angle R1 R2 R3 R4 R5 R6 R7 R8
5.00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
19.75 0.00035 0.00020 0.00027 0.00033 0.00027 0.00035 0.00040 0.00022
45.00 0.00090 0.00038 0.00062 0.00088 0.00060 0.00067 0.00072 0.00050
90.00 0.00120 0.00060 0.00087 0.00108 0.00095 0.00097 0.00102 0.00073
135.00 0.00090 0.00038 0.00062 0.00088 0.00060 0.00067 0.00072 0.00050
160.25 0.00035 0.00020 0.00027 0.00033 0.00027 0.00035 0.00040 0.00022
175.00 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000


OEM-Rod-Bolt-Eccentricity.jpg

ARP-625 rod bolts

Torque specification

Measurements and rod bore distoration

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