Engine Specs - S65/S85 Rod Bolts
Contents
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.
- Lubricate rod bolt threads and connecting rod cap bore holes with appropriate thread lubricant.
- Torque to 20-Nm, then using a torque-angle gauge tighten another 130-degrees.
- Remove bolts.
- Repeat steps 1-3
- Repeat steps 1, 2.
Specifications: Clamping force
Approximately 11000 pounds forceTorque specification
Specifications: Measurements
| Angle | R1 | R2 | R3 | R4 | R5 | R6 | R7 | R8 |
| 5.00 | 2.20490 | 2.20495 | 2.20520 | 2.20500 | 2.20510 | 2.20510 | 2.20515 | 2.20510 |
| 19.75 | 2.20490 | 2.20500 | 2.20510 | 2.20500 | 2.20500 | 2.20520 | 2.20510 | 2.20510 |
| 45.00 | 2.20500 | 2.20510 | 2.20515 | 2.20520 | 2.20500 | 2.20500 | 2.20500 | 2.20520 |
| 90.00 | 2.20510 | 2.20530 | 2.20515 | 2.20540 | 2.20515 | 2.20510 | 2.20515 | 2.20520 |
| 135.00 | 2.20500 | 2.20520 | 2.20520 | 2.20520 | 2.20510 | 2.20515 | 2.20500 | 2.20520 |
| 160.25 | 2.20500 | 2.20510 | 2.20520 | 2.20500 | 2.20520 | 2.20520 | 2.20510 | 2.20515 |
| 175.00 | 2.20500 | 2.20500 | 2.20520 | 2.20500 | 2.20520 | 2.20530 | 2.20510 | 2.20515 |
