How do I know when a rod bolt needs to be replaced?

Per the chart instructions, if any rod bolt has stretched by .001 or more from its original relaxed-length measurement, it should be replaced immediately — it has gone past its yield point and is prone to failure.

When should rod bolt length be measured?

Measure each bolt in the "relaxed" (untorqued) condition prior to installing the rods and record it on the chart, then measure again at teardown for maintenance.

What tool is used to check rod bolt condition?

A stretch gage is used to measure the length of each rod bolt.

Does bolt location matter when re-measuring?

Yes — the instructions say to be careful to keep each rod bolt in the same location as the original installation.

What measurements does the chart record?

For each rod (e.g., ROD #1, #2, #5, #6) there are blanks for the INSIDE BOLT and OUTSIDE BOLT, each with 'IN' and 'OUT' fields for recording bolt lengths.

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Rod Bolt Stretch Monitoring Chart & Instructions - Connecting Rod Bolt Gauge Log

Rod Bolt Stretch Monitoring Chart, partial view with stretch-gage instructions and rod fields

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Rod bolt stretch monitoring chart showing stretch-gage instruction text alongside inside/outside bolt measurement fields.

AI caption July 2017 · Photo 25 of 138

This document is a Rod Bolt Stretch Monitoring Chart, apparently part of connecting rod or rod bolt packaging/instructions. The left column contains instructions explaining the importance of monitoring rod bolt condition using a stretch gage: before installing the rods, each bolt's length should be measured in the "relaxed" (untorqued) condition and recorded on the chart. At engine teardown for maintenance, each rod bolt is measured again, keeping each bolt in its original location. If any rod bolt has stretched by .001 inch or more from the original measurement, it must be replaced immediately because it has exceeded its yield point and is prone to failure. The visible portion of the chart provides fill-in blanks for ROD #1, ROD #2, ROD #5, and ROD #6, each with lines for an INSIDE BOLT and an OUTSIDE BOLT, and "IN" and "OUT" measurement fields for each. (Cells for other rods, e.g., #3, #4, #7, #8, are presumably on portions of the card not visible in this photo.) The document is undated and does not identify a specific vehicle make, model, or part number; it is a generic engine-building reference for tracking rod bolt stretch over the life of the engine.

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Frequently asked questions

How do I know when a rod bolt needs to be replaced?: Per the chart instructions, if any rod bolt has stretched by .001 or more from its original relaxed-length measurement, it should be replaced immediately — it has gone past its yield point and is prone to failure.
When should rod bolt length be measured?: Measure each bolt in the "relaxed" (untorqued) condition prior to installing the rods and record it on the chart, then measure again at teardown for maintenance.
What tool is used to check rod bolt condition?: A stretch gage is used to measure the length of each rod bolt.
Does bolt location matter when re-measuring?: Yes — the instructions say to be careful to keep each rod bolt in the same location as the original installation.
What measurements does the chart record?: For each rod (e.g., ROD #1, #2, #5, #6) there are blanks for the INSIDE BOLT and OUTSIDE BOLT, each with 'IN' and 'OUT' fields for recording bolt lengths.