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Measuring rod bolts accurately in there free standing length

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I’m wondering if anyone can help me..

I want to measure my ARP 2000 rod bolts accurately before first installation, so there free standing length. I can note down the lengths so when it comes to a rebuild I can measure them again (free standing) to make sure they have not been compromised/overstretched. It says if they are 0.001” longer from when they were new they will need replacing.

I’ve read a manual and it says to measure the free length of the bolts with a stretch gauge or micrometer. I don’t have a micrometer with ball end attachments so will be unable you use a micrometer to get accurate enough results. Can anyone tell me how I can use a stretch gauge to measure the free standing length of the bolts. I can’t seem to find any info on it and can’t work out in my head how I would be able do it accurately. I thought the stretch gauge can only measure stretch at a installed state?

The only way I can think of is if you set the dial gauge needle/pointer at a random point on the dial gauge and stick with that exact point every time. Then fitted the bolt and write the measurement down, as long as your stretch gauge wasn’t adjusted/dropped till the next time you measured it you could measure it again at that same point and this would tell you if the bolt has been stretched in its free standing state.

I hope that makes sense

Thanks in advance


Hey Ryan,

This is a good question. There a few answers depending on your availability of tools. You touched on this and I'd like to emphasize that a stretch gauge is a comparison tool, not a direct measuring tool. It is highly impractical to leave a stretch gauge assembled and in the exact same position...good chance of it getting bumped and loosing its zero. What you need is a standard to zero this gauge off of. Ideally this would be a stack of gauge blocks but not everyone has a set on hand. You can also use a spare rod bolt and zero your stretch gauge off of that. Given that you have a flat micrometer you can also attempt to measure over ball bearings, which sounds better in theory than practice unless you have three hands. You can also get inexpensive slide on micrometer tips that nest on your mic's flat anvil I'm sure there are a few more methods I'm not thinking of right now. Whichever way you choose it obviously needs to be repeatable, which means you need to be comfortable performing it.



Hi Ryer

Thanks for the reply.

I have a few spare rod bolts somewhere, so that seems like a good way to do it. Use a spare bolt to zero the gauge. As long as I keep and don’t lose that bolt.

I will look into some anvil tips as that seems like it’ll be the most accurate as I have vernier micrometers so I can read down to 0.001mm.