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SAE J616-2008: Engine Foot Mounting Dimensions and Design Guidance
SAE J616 is a recommended practice that specifies foot mounting dimensions for engines intended for installation on subbases. Originally issued in 1957 and last revised in 1995, the standard was cancelled in July 2008 after the Powertrain Systems Group could not assemble the necessary subject matter experts for its mandatory five-year review. Despite its cancelled status, the dimensional data in J616 still represents a commonly used reference for engine foot mounting configurations on flywheel housings.
Overview of SAE J616
The standard covers both front and rear mounting brackets, providing a consistent set of dimensions for flywheel housings designated by numbers 00 through 6. The dimensions are presented in both millimeters and inches, reflecting both international and domestic design practices. The key mounting dimensions—labeled A, B, C, D, and E in Table 1—define the spacing, hole diameters, and number of bolt holes per side for each housing size.
⚠️ Important Note on Cancellation: SAE J616 was cancelled in July 2008 because the responsible committee could not convene experts for the required five-year review. Before using these dimensions in new designs, verify whether a replacement or updated standard applies, or consult the engine manufacturer for current specifications.
Key Dimensional Specifications
Table 1 provides the critical dimensions for engine foot mounting. Dimension A includes a footnote requiring the subbase to allow clearance for engine components that extend below this dimension. Tolerances are clearly specified: for dimension A, ±0.25 mm (±0.010 in); for the bolt hole diameter E, +0.30/–0.10 mm (+0.012/–0.004 in).
| Flywheel Housing No. | A (mm) | A (in) | B (mm) | B (in) | C (mm) | C (in) | D (mm) | D (in) | E Bolt Hole Dia (mm) | E Bolt Hole Dia (in) | Front Bolt Holes Each Side | Rear Bolt Holes Each Side |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 00 | 457.2 | 18.00 | 425.4 | 16.75 | 35.0 | 1.38 | 63.5 | 2.50 | 20.6 | 0.81 | 2 | 1 |
| 0 | 368.3 | 14.50 | 342.9 | 13.50 | 35.0 | 1.38 | 63.5 | 2.50 | 20.6 | 0.81 | 2 | 1 |
| 1/2 | 336.6 | 13.25 | 317.5 | 12.50 | 35.0 | 1.38 | 63.5 | 2.50 | 20.6 | 0.81 | 2 | 1 |
| 1 | 292.1 | 11.50 | 266.7 | 10.50 | 35.0 | 1.38 | 63.5 | 2.50 | 20.6 | 0.81 | 2 | 1 |
| 2 | 260.4 | 10.25 | 241.3 | 9.50 | 35.0 | 1.38 | — | — | 20.6 | 0.81 | 1 | 1 |
| 3 | 241.3 | 9.50 | 215.9 | 8.50 | 35.0 | 1.38 | — | — | 20.6 | 0.81 | 1 | 1 |
| 4 | 215.9 | 8.50 | 190.5 | 7.50 | 35.0 | 1.38 | — | — | 17.5 | 0.69 | 1 | 1 |
| 5 | 190.5 | 7.50 | 171.4 | 6.75 | 35.0 | 1.38 | — | — | 17.5 | 0.69 | 1 | 1 |
| 6 | 165.1 | 6.50 | 146.0 | 5.75 | 35.0 | 1.38 | — | — | 14.2 | 0.56 | 1 | 1 |
Note: Dimension D is not specified for housings 2 through 6. All dimensions in inches are nominal conversions; tolerances apply to mm values.
Engineering Design Insights
🛠️ Subbase Allowance for Dimension A: The footnote for dimension A explicitly states that the subbase must provide allowance for engine components which extend below this dimension. This is a critical design constraint often overlooked—ensure that oil pans, filters, or other protruding elements do not interfere with the subbase structure.
Tolerance and Fit: The tolerances for A (±0.25 mm) and bolt hole diameter E (+0.30/–0.10 mm) are relatively tight. When designing mating brackets, consider worst-case stack-ups to avoid interference or excessive play.
Bolt Hole Count Variations: Larger housings (00 through 1) feature 2 front and 1 rear bolt hole per side, while smaller housings (2 through 6) have 1 front and 1 rear. This reflects the increased load capacity of larger engines.
🔍 Design Insight: Always verify the specific flywheel housing number before selecting mounting dimensions. Using the wrong configuration—or failing to account for the subbase allowance—is a common mistake that can lead to costly redesigns.
Common Mistakes to Avoid:
- Assuming the cancelled standard is still active—check for newer references or consult the engine manufacturer.
- Confusing imperial and metric values or misapplying tolerances.
- Overlooking the subbase allowance for components extending below dimension A.
- Interchanging front and rear bolt hole counts.
Frequently Asked Questions
- Why was SAE J616 cancelled?
It was cancelled because the SAE Powertrain Systems Group could not assemble a panel of subject matter experts to conduct the required five-year review. Without expert input, the standard could not be reaffirmed or revised. - Is there a replacement standard for SAE J616?
No direct replacement was issued upon cancellation. Engineers should refer to current SAE standards such as SAE J1174 (Engine Mounting) or consult with the engine manufacturer for up-to-date mounting specifications. Some original data may still be used if verified. - What are the most critical dimensions for subbase design?
Dimension A and its subbase allowance are critical for ensuring proper clearance. Dimensions B and C determine lateral and vertical mounting locations, while bolt hole diameter E and bolt hole counts ensure secure fastening. - Can I still use SAE J616 dimensions for legacy designs?
Yes, for legacy engines that were originally designed to this standard. However, for any new design, verify dimensions directly from the engine manufacturer or a current standard to ensure compliance with modern requirements.
By understanding the details of SAE J616, engineers can avoid common pitfalls and apply sound design practices for engine foot mounting. Even as a cancelled standard, it remains a valuable reference for many existing powertrain installations.
