Summit Racing Rod Bolt Stretch Gauge Review

[Gordo2]

I just finished installing my ARP rod bolts using the Summit Racing stretch gauge. Figured I would provide a review on the tool since I couldn't seem to find any info detailing the pro's and con's or use on 911 engines.

This is the gauge I purchased from Summit:



Pro's

- The complete gauge was ~$60 from Summit; about $100 less than the gold standard, ARP rod bolt stretch gauge.

- The tool accomplished the job. I'm confident that the Summit gauge provided reasonably accurate stretch measurements.

- The pins fit into the ARP bolt dimples well. I found that I could press/hold the bottom pin into the bolt and move the top pin (attached to the dial indicator) around the dimple on the bolt head to find the shortest possible measurement.

I guess that's it - an unfortunately short list of the pro's...

Con's

- The instructions are worthless, nuff said on that one.

- Assembly wasn't bad, but the damn thing has 3 different sized allen head bolts. One of the allen heads seemed to be metric and nothing fit the other 2 (and I have sets of both metric and standard allen keys). Have the Chinese created their own allen head sizes



- The tool is difficult to manage. The spring on the dial gauge is too weak allow it to remain hung from a rod bolt horizontally and if you try to attach the gauge vertically/ upright (dial above the bolt), you will find the weight of the gauge fully compresses the spring/dial. As such, your best bet is to hold the gauge horizontally on the bolt.

Due to the weak dial gauge spring, getting accurate measurements pretty much requires both hands. The idea of keeping a box end wrench on the bolt as you torque/stretch to length is totally out of the question with this one.



- The dial gauge has an odd protrusion on the back. I guess you could use this to hang the gauge from a tool rack or something, but it does a much better job of getting in the way - limiting options for how you can attach the stretch gauge to the bolt.



The Bottom Line

Would I buy it again - possibly, but only because I believe installing rod bolts to a stretch length is more accurate and provides greater rod bolt durability/rod end durability than a single torque spec provides.
Couple this with the fact that it relatively inexpensive - which is important when you are buying what is for most DIY builders, a one time use tool.

Had I known the tool was going to be the A$$ pain that it was, I might have considered buying the ARP rod stretch gauge and selling it when I was done.

So there you have it.

Gordo

[Tom '74 911]

Great review and info. Thanks for taking the time!
Tom

[jhg41977]

Possibly a dumb question but why not hang the gauge upside down vertical?

[Jcslocum]

The mount on the back is to fix the gauge to a mag block or a flex arm to do many different measurements with the same gauge.

You're not supposed to hold the gauge on there while tightening the nut. For this application, you are using the mic to load verify after torquing. They give a range and you check them once you have torqued and then touch up if needed.

You measure or try to, in the same spot each time and take 3 measurements and then average them for the final. Getting good measurements is hard and takes some practice and skill. Even on large bolts/studs you would think it's easy....

Looks like you have it all in hand and are doing very good work. I'm enjoying the build very much. Keep the posts and info coming!!!!

[Gordo2]

Originally Posted by jhg41977

Possibly a dumb question but why not hang the gauge upside down vertical?

Not a dumb question at all - I tried every possible mounting configuration figuring something had to be easier...

This may be difficult to picture, but you can only attach the stretch gauge one way - with the dial at the big end of the rod. If you try to attach it with the dial toward the small end of the rod, the dial and/or the gauge assembly contacts connecting rod, making it impossible to mount the gauge on the bolt this way.

As such - if you tried to mount the Summit gauge vertically, with the dial hanging down and the bottom of the too mounted to the top of the bolt (so the gauge spring wasn't compressed under it's own weight), the connecting rod would also be hanging down - making it so you couldn't mount the gauge.

At first, I thought this was just a poor design of the Summit gauge, but it looks like the ARP gauge is the same - as far as mounting so the gauge is on the big end goes. Every picture I pulled up showed the ARP tool mounted with the gauge on the big end - an example:



Meanwhile, in this picture you will notice that the gauge is semi-vertical - which is only possible because the ARP gauge has a dial gauge spring that is strong enough to support the weight of the tool and still take the measurement.

If I tried to position the Summit gauge similar to how the ARP gauge is pictured, the weight of the tool assembly would max the dial gauge out.

My best shot at an explanation - hope it helps.

Note in response to Jon's comment: "You're not supposed to hold the gauge on there while tightening the nut."
The ARP gauge clearly allows you to do so and I found a bunch of instructions on the web describing the process.

The process I used was:
- Zero the gauge on the un-tensioned/un-torqued bolt
- Remove the gauge
- Torque to 38 ft-lbs (a torque that I found most of the bolts started to creep toward their stretch spec).
- Add 1-2 ft-lbs to the torque wrench and re-torque.
- Re-measure and repeat, sometimes at .5 ft-lb increments to get to the required stretch length.

Thanks for the feedback folks.
Gordo

[Jeff Alton]

The ARP gauge in the pic above doesn't look like the ones we have. Ours have the billet frame. The dial indicator looks the same and it is high tension which allows it to remain in place while you stretch the bolt. We have another stretch gauge from a parts warehouse that doesn't have the required tension. It sits in the drawer and collects dust...

[shbop]

By using a combination wrench, you can leave the gauge on the fastener as you stretch the bolt the proper amount. I can't imagine having done this, if I had to remove and re-install the gauge as I stretched each bolt.

[boyt911sc]

Originally Posted by Gordo2

Not a dumb question at all - I tried every possible mounting configuration figuring something had to be easier...

This may be difficult to picture, but you can only attach the stretch gauge one way - with the dial at the big end of the rod. If you try to attach it with the dial toward the small end of the rod, the dial and/or the gauge assembly contacts connecting rod, making it impossible to mount the gauge on the bolt this way.

As such - if you tried to mount the Summit gauge vertically, with the dial hanging down and the bottom of the too mounted to the top of the bolt (so the gauge spring wasn't compressed under it's own weight), the connecting rod would also be hanging down - making it so you couldn't mount the gauge.

At first, I thought this was just a poor design of the Summit gauge, but it looks like the ARP gauge is the same - as far as mounting so the gauge is on the big end goes. Every picture I pulled up showed the ARP tool mounted with the gauge on the big end - an example:



Meanwhile, in this picture you will notice that the gauge is semi-vertical - which is only possible because the ARP gauge has a dial gauge spring that is strong enough to support the weight of the tool and still take the measurement.

If I tried to position the Summit gauge similar to how the ARP gauge is pictured, the weight of the tool assembly would max the dial gauge out.

My best shot at an explanation - hope it helps.

Note in response to Jon's comment: "You're not supposed to hold the gauge on there while tightening the nut."
The ARP gauge clearly allows you to do so and I found a bunch of instructions on the web describing the process.

The process I used was:
- Zero the gauge on the un-tensioned/un-torqued bolt
- Remove the gauge
- Torque to 38 ft-lbs (a torque that I found most of the bolts started to creep toward their stretch spec).
- Add 1-2 ft-lbs to the torque wrench and re-torque.
- Re-measure and repeat, sometimes at .5 ft-lb increments to get to the required stretch length.

Thanks for the feedback folks.
Gordo

Gordo,

I only did two (2) engines so far with ARP rod bolts using the stretch and torque method combo. Both times my data were very tight and reproducible. The difference between our technique was that I used a control bolt (point) as ZERO point. Then took three (3) readings on each rod bolts (with ID #). Install them in sequence, with ARP lubricant, and applied the torque. Measure the con rod bolt per rod three (3) times and tabulate. Proceed to the next connecting rod and so on. After doing 2 con rods, the stretch gauge was rechecked using the control bolt to determine any change in the setting. The reliability of your measurement depends a lot on the quality and accuracy of the dial indicator you used.

Re-setting the dial indicator each time you measure a con rod bolt like you did would introduce a variable (negligible or not). Does the dial indicator go back to set-point 10 times out of 10 or less? How do you know or verify that the stretch gauge has not been affected during usage? So having control or standard is needed for a good metrology.

Tony

[peppy]

Here is a picture of the one I used from JEGS. This one seams a bit more like the ARP one.



I also did not remove the gauge to tighten the bolts.

[Gordo2]

Originally Posted by peppy

Here is a picture of the one I used from JEGS. This one seams a bit more like the ARP one.



I also did not remove the gauge to tighten the bolts.

Beautiful - wishing I would have bought the Jegs Stretch gauge instead of the Summit. Looks like it is ~ $80.

A couple of notes from your picture of the Jegs rod bolt stretch gauge:

- Shows that with the right gauge, you can have the dial at either the big or the small end of the connecting rod (which I can't do with my Summit Stretch gauge).

- Shows the Jegs stretch gauge dial has enough spring tension to remain on the bolt without holding it in place - allowing you to tighten the bolt while the stretch gauge remains attached.

- Shows how most online procedures recommend stretching rod bolts: with the gauge attached, a box end wrench on the nut - torque until you get to the desired length.


In part, I bought the Summit tool because it looked just like the more expensive (~$240) ARP stretch gauge tool that I posted in the previous picture.

------------------------------

Reply to shbop's post "I can't imagine having done this, if I had to remove and re-install the gauge as I stretched each bolt".

Exactly - a PITA. Unfortunately, I didn't figure out any other option with the Summit tool.

Gordo

[Gordo2]

Originally Posted by boyt911sc

...I used a control bolt (point) as ZERO point. Then took three (3) readings on each rod bolts (with ID #). ... After doing 2 con rods, the stretch gauge was rechecked using the control bolt to determine any change in the setting.

The reliability of your measurement depends a lot on the quality and accuracy of the dial indicator you used.

Re-setting the dial indicator each time you measure a con rod bolt like you did would introduce a variable (negligible or not). Does the dial indicator go back to set-point 10 times out of 10 or less? How do you know or verify that the stretch gauge has not been affected during usage? So having control or standard is needed for a good metrology.
Tony

Tony,

I think what's most important is consistency of process - how you take the measurements.

On the other hand, your measurements assume that each rod bolt is the exact same length from the manufacturer - which isn't necessarily the case, as discussed here:

Measuring ARP Rod Bolt Stretch - Micrometer vs. Stretch Gauge

My rod bolt lengths varied by some small amount (though in the linked post I said they were the same length as measured from the dimples - there was in fact minor deviations), therefore I zero'd the gauge for each bolt and stretched to 0.01".

"Metrology" - don't know where you are, but the weather sucked here .

All good,

Thanks, Gordo

[Walt Fricke]

I've used Raceware and ARP rod bolts with a Summit (or Summit style) gauge. The bolts were always slightly different lengths, but I didn't really care if my initial setting of the gauge was all that accurate - I used micrometer setting rods, and those have flat ends so they are iffy for setting an anvil ended instrument, no? But the indicated stretch is more like a percentage of relaxed length, and small changes in the initial set of the gauge aren't going to affect the process, are they? Measure bolt relaxed and write it down (easiest if you have a laptop there and enter it into a spread sheet, which will do the math telling you what you are shooting for), torque, measure and see how much longer it is, torque a bit more depending on how far off you are, repeat until in the range specified.

For some reason it never occurred to me to tighten the nut with the gauge in place. Perhaps because the spring in the indicator wasn't strong enough. Although dial indicators are inexpensive, and I've fitted several different ones in my stretch gauge.

Or perhaps because I needed the extra length of the torque wrench with a socket at the 50+ lbs/ft level.

So it was measure, remove, retighten, replace, measure, retighten.

I didn't think to measure 3x and average. Is there that much variation in how the anvils fit the dimples? I'd just wiggle around until I got the smallest reading, which I took to be the one where the anvils were best seated in the dimples, and use that.

It would be nice to torque watching the gauge needle move until it was where you wanted, and call it good, though. Sort of like how you can set the older style 911 cams. If I had a shop I am sure I'd want to be more efficient than I am.

[burgermeister]

I own a JEGS stretch gage. Mine does not have sufficient tension to stay in place by itself. Also, the round "ball" point on the indicator side is a poor fit in the bolt dimples.

I fixed this by buying a HF point set, which has a short 60deg (I think) conical point that fits the dimples nicely. Or you could turn one if you have a lathe. A trip to the hardware store yielded a suitable washer, to be captured between the point and the indicator shaft, and an appropriate spring. I simply unscrewed the ball point, added the spring & washer & screwed in the cone point. Now there is sufficient tension to hold everything in place.

If you squish some 1/2" (I think; maybe it was 3/4") EMT in a vise it makes a great handle for the standard box wrench, which is a bit short for 50 ft*lb of torque.

I'd take a picture, but a friend has my rebuild tools for the winter.

[boyt911sc]

Originally Posted by Gordo2

Tony,

I think what's most important is consistency of process - how you take the measurements.

On the other hand, your measurements assume that each rod bolt is the exact same length from the manufacturer - which isn't necessarily the case, as discussed here:

Measuring ARP Rod Bolt Stretch - Micrometer vs. Stretch Gauge

My rod bolt lengths varied by some small amount (though in the linked post I said they were the same length as measured from the dimples - there was in fact minor deviations), therefore I zero'd the gauge for each bolt and stretched to 0.01".

"Metrology" - don't know where you are, but the weather sucked here .

All good,

Thanks, Gordo

Gordo,

Each connecting con rod was measured multiple times and recorded. Installed, torqued, and measured again multiple times. The difference in length is the 'stretch'. I never assumed the con rods were identical in length. Where did you get that idea?

Tony

[Gordo2]

Originally Posted by boyt911sc

Gordo,

Each connecting con rod was measured multiple times and recorded. Installed, torqued, and measured again multiple times. The difference in length is the 'stretch'. I never assumed the con rods were identical in length. Where did you get that idea?

Tony

Tony,

Your reply doesn't really sound like the same discussion

When you refer to connecting rod - do you mean connecting rod bolts (& associated lengths)?

In response, I'm going to assume you mean connecting rod bolts:

You originally posted "I used a control bolt (point) as ZERO point" - which I understood as - one rod bolt was placed in the stretch gauge; the gauge was zero'd and then you measured the amount that each rod bolt stretched (as you torqued them) as compared to your original rod bolt. In other words, you used one bolt as a standard and based the stretch length on this one bolt.

Not saying this is wrong; just confirming your process and basis for how you determined the amount of stretch per rod bolt.

If I'm understanding correctly, my issue with this method was that I found the original rod bolts have slightly different lengths (as compared with both micrometer and when placed in my stretch gauge). As such each connecting rod bolt needed to be initially zero'd on the stretch gauge and then torqued/stretched to the ARP recommended spec.

Thanks, Gordo