I bought a ARP stretch gauge a couple of years ago and used it on a few engines so far. Its nowhere near as easy as the old days when we just slowly torqued the rod bolts up to a given number. Since its Winter and things are slow around here what are your thoughts on a few things. After your bolts have been cycled a couple of times and are in the process of putting the engine together do you.
1. Install stretch gauge on the first bolt and torque to given stretch factor, move to second rod bold and do the same to the second bolt on the same rod. And if doing so do you think the stretch factor on the first bolt changed. I know from testing that doing it the old way of just torquing bolts when you went back and forth the torque number changed.
2. What tool do you find the easiest to use on final assembly to apply torque. Sockets are out with the stretch gauge in place. I bought a snap on crows foot and it didn't really work that great. I was thinking of buying the longest box end wrench and welding an extender on it if I have to. What tool did you guys find the easiest to slowly creep up on the stretch point?

Never used one myself just figured torque was enuff since I`ve had zero failures due to rod bolts and long before that gauge was around, torque readings alone were enuff. After hearing how some have needed to go 20+ ft lbs to get desired stretch, that too is another reason not to use one plus as you`re holding the gauge in your hand body heat becomes a factor in accurate numbers...........call me crazy.............

I bought a rod bolt stretch gauge form Comp Cams tool company, CRS I like it, I don't try to measure the stretch while torquing the bolts, I set the gauge to zero with no pressure on the bolt, one side at a time, and then apply something less than the recommend torque that the rod bolts call for, I torque the bolt on one side and remeasure it. Usually they are not as long as recommended so I increase the torque on the wrench between 2 to 5 ft. lbs. and retorque and remeasure until I get the stretch in the middle of the recommended range, IE with .0057 to .0062 recommended I shoot for .0060 It does take time but I'm happy with the results so far Make sure your gauge reads in .00010, not .0010 range. Some of the rod makers want you to stretch the bolst three times before measuring them for final stretch, I haven't seen any of them vary more than .00010 by doing that I did see 20 ft lbs differences needed to make the length the same on a set of rod bolts in a set of Oliver billet steel rods They must have mixed that set of bolts from two different rod bolt batches I wanted them to replace all of the bolts and they siad no way, it was common for them to see that much differences needed to get them within .0001 They wanted me to use the torque plus so many degrees method instead of uisng torque settings with the rod bolt stretch gauge

I don't like to "slowly" creep up on stretch. If they don't stretch enough I start over and torque in 3 steps. Even w/ the lube , I believe there is still some break-away that can goof up the final step.

Don't likem. Won't usem. IMO, too many variables to try to get an accurate reading out to 4 places - and just too close to experience a major clamping failure. I just can't put that much faith in the bolt Mfgs.

I use it just for to keep track of the bolts after i TQ the bolt to spec i measure each bolt put in my file then the next time i change bearing i can look at file and see if anything has changed and see if the bolts need changed ! i do not use it while TQ only when i am done! to have a ref.

Many times I have seen fastener stretch increase 50% just by cycling it a few times. I loosen the bolt completely (this allows the lube to be redistributed from one side of the threads to the high pressure side) and push in new lube under the bolt head. Initially and when you are getting close to the desired number it is a good idea to remove the bolt completely, clean the threads and re-apply new assembly lube. The goal is to get as much rotational energy into stretching rather than lost in head/thread friction. I dont go over the maximum recommended torque, I think they list this to avoid running the risk of over twisting the fastener.

It does take a while to get the hang of using the gauge. Also, you can affect the reading by changing or putting too much tension on the gauge. If your gauge has a needle sharp tip like mine did, rounding it slightly may help it find the center of the bolt to get a more accurate reading.

BTW, all this takes a good bit of time and I doubt most shops go to the trouble.

Interesting reading

onnecting Rod Bolt Torque Specifications

ROD BOLT STRETCH & TORQUE SPECIFICATIONS

The following information is vital for the proper connecting rod assembly installation:

STEP 1:
Your Crower connecting rods came with a connecting rod specification tag. Check the tag to find the rod bolt part number used to fasten your connecting rods. Rod bolt length listed here is the measurement from under the head to the end.
STEP 2:
Use the chart below to determine the recommended lubricant, rod bolt stretch and torque amounts.

*IMPORTANT* DO NOT EXCEED THE TORQUE AMOUNT SHOWN BELOW FOR EACH BOLT PART NUMBER AND ITS RECOMMENDED LUBRICATION (If you are using lubrication other than shown below, a stretch gauge must be used)
Connecting Rod Bolt Specification Steel Connecting Rods Titanium Connecting Rods
Part # Diameter x U.H.Length PSI Material Assembly Lubricant Bolt Stretch Torque Assembly Lube Bolt Stretch Torque
90800 7/16" x 2.000" Crower #90894 * .005"-.007" 70 ft lbs
90802 7/16" x 1.700" 20W/50 Motor Oil .004"-.006" 65 ft lbs
90803 7/16" x 1.940" 20W/50 Motor Oil .004"-.006" 65 ft lbs
90804 7/16" x 2.320" 20W/50 Motor Oil .004"-.006" 65 ft lbs
90805 3/8" x 1.920" 20W/50 Motor Oil .004"-.006" 50 ft lbs
90806 11/32" x 1.940" 20W/50 Motor Oil .004"-.006" 35 ft lbs
90807 7/16" x 2.070" 20W/50 Motor Oil .004"-.006" 65 ft lbs
90809 1/2" x 2.500" Crower #90894* .005"-.007" 95 ft lbs
90817 5/16" x 1.500" Crower #90894 * .005"-.007" 25 ft lbs Crower Lube #90897 .005"-.007" 25 ft lbs
90818 3/8" x 1.600" 220,000 H-11 Crower #90894 * .005"-.007" 45 ft lbs Crower Lube #90897 .005"-.007" 50 ft lbs
90819 3/8" x 1.600" 220,000 H-11 Crower #90894 * .004"-.006" 45 ft lbs Crower Lube #90897 .005"-.007" 50 ft lbs
90820 7/16" x 1.800" 220,000 H-11 Crower #90894 * .005"-.007" 75 ft lbs Crower Lube #90897 .005"-.007" 75 ft lbs
90821 3/8 x 1.600 220,000 ARP2000 Crower #90894* .005"-.007" 45 ft lbs Crower Lube #90897
.005"-.007"
45 ft lbs
90823 7/16" x 1.650" 220,000 H-11 Crower #90894 * .005"-.007" 75 ft lbs Crower Lube #90897 .005"-.007" 75 ft lbs
90824 5/16" x 1.500" 220,000 H-11 Crower #90894 * .005"-.007" 30 ft lbs Crower Lube #90897 .005"-.007" 35 ft lbs
90824A 5/16" x 1.500" 220,000 ARP2000 Crower #90894 * .005"-.007" 30 ft lbs Crower Lube #90897 .005"-.007" 25 ft lbs
90825 7/16" x 1.700" 220,000 H-11 Crower #90894 * .005"-.007" 75 ft lbs Crower Lube #90897 .005"-.007" 75 ft lbs
90826 7/16" x 1.540" 220,000 H-11 Crower #90894 * .005"-.007" 75 ft lbs Crower Lube #90897 .005"-.007" 75 ft lbs
90826A 7/16" x 1.550" 220,000 ARP2000 Crower #90894 * .005"-.007" 75 ft lbs Crower Lube #90987 .005"-.007" 65 ft lbs
90827 3/8" x 1.600" 220,000 H-11 Crower #90894 * .005"-.007" 45 ft lbs Crower Lube #90897 .005"-.007" 50 ft lbs
90828 3/8" x 1.600" 180,000 8740 Crower #90894 * .005"-.007" 45 ft lbs
90829 7/16" x 1.800" 180,000 8740 Crower #90894 * .005"-.007" 75 ft lbs
90830 7/16" x 1.540" 280,000 AMS Crower #90894 * .005"-.007" 95 ft lbs Crower Lube #90897 .005"-.007" 95 ft lbs
90831 7/16" x 1.700" 280,000 AMS Crower #90894 * .005"-.007" 95 ft lbs Crower Lube #90897 .005"-.007" 95 ft lbs
90832 7/16" x 1.800" 280,000 AMS Crower #90894 * .005"-.007" 95 ft lbs Crower Lube #90897 .005"-.007" 95 ft lbs
90833 7/16" x 1.650" 280,000 AMS Crower #90894 * .005"-.007" 95 ft lbs Crower Lube #90897 .005"-.007" 95 ft lbs
90842 3/8" x 1.600" 280,000 AMS Crower #90894 * .005"-.007" 65 ft lbs Crower Lube #90897 .005"-.007" 50 ft lbs
90845 5/16" x 1.500" 280,000 AMS Crower #90894 * .005"-.007" 40 ft lbs Crower Lube #90897 .005"-.007" 35 ft lbs
90846 7/16" x 1.440" 180,000 8740 20W/50 Motor Oil .005"-.007" 75 ft lbs
90847 1/4" x 1.375" 280,000 AMS Crower #90894 * .005"-.007" 275 in lbs Crower Lube #90897 .005"-.007" 240 in lbs
90848 7/16" x 1.400" 180,000 8740 Crower #90894 * .005"-.007" 75 ft lbs

* Note: Crower #90894 is ARP Ultra Torque Lubricant . Not all bolts listed are currently available.
STEP 3:
Taking the necessary precautions to protect the rod surfaces, secure the rod in a vise and leave the cap free to float. If the rod is titanium, take extra precautions to avoid damaging the plasma coating on the big end sides of the rod.
STEP 4:
Apply a liberal amount of the recommended assembly lubricant to the bolt's threads and under the head of the bolt (the underside of the bolt's head).
STEP 5:
(Use Stretch Method to determine exact torque) Since it is near impossible to use a stretch gauge when installing rods inside the motor, please use the following method to determine the exact torque that your wrench will read when the correct stretch is achieved. Using the above table, torque the rod bolts to achieve the required amount of stretch for your application. Record this torque spec as this is the exact torque spec that you will be using to install your rods in the motor.
STEP 6:
(Torquing the bolt) When tightening bolts, especially in titanium rods it is best to torque all bolts to 20% of the total required torque and then in one smooth motion torque the bolt to the final torque spec without stopping.

Torquing your rod bolts without pre-determining the required torque to achieve the correct rod bolt stretch is not recommended. However if this is the only tightening method available to you, DO NOT EXCEED THE TORQUE AMOUNT INDICATED FOR YOUR BOLTS.

NOTE: Your Crowerods are totally rebuildable. We can make most used rods like new again, replace bolts, replace bushings, resize them, respray the plasma on Titanium rods and freshen them up as needed. If you have any questions as to the durability and application of your rods or whether it is time to rebuild or replace them, please call our tech line at (619) 661-6477 or email us at rods@crower.com

I still use the old torque method on all my racing stuff, but have been using the bolt stretch method for about 30 years at work. No doubt that the stretch method is the best, but think most of you guys are worrying way to much about it, you just need to stretch the bolt the required amount, no need to worry about how many times, ect. You do want to use good lube ect so you dont damage threads trying to stretch the bolt. We have some bolts we use a special miccrometer to measure length, some a indicator setup to check lenth, and then some we use a hydrotourqe wrench and just pull bolt so many pounds, then just hand tighten the nut. I've rechchecked the hydratorqued bolts and the pounds method is allways allways right on on stretch. We mainly though use that method on studs, headbolts, main studs, main crossbolts, ect. I'd use some of this equipment at home on my car, but its all way to big. The stretch method works just fine, really the most accurate, but if you have good threads, and use the correct lube, torqueing is just fine.

A lot of the major rod bolt manufacturers no longer want to give a specific torque number anymore. Some have gone as far as taking down their websites that had them listed.

Some of you guys say you won't use a gage and thats what I thought too until I went to use a set of K1's which had no torque specs, only stretch specs.

I did mine in a vise first where it it was fairly easy to use a mic, they all came out @ 82 lbs which made it easy when I assembled it later, might not be the exact way to do it but its done.

One more thing I had two that acted funny at first but later I realized what prolly happened, they were not as tight when took them apart and the didn't want to stretch like like the others right away and that was because they were not torqued up to the stretch value which eventually worked after they were torqued up twice

Geez sorry long

Mitch

I suspect the stretch guage method is a way to compensate for all the people with crap torque wrenches or stuff that hasn't been calibrated since Christ was a corporal. 75lb/ft at ARP is different than 75lb/ft at Zeke's Race Engines,Liquor and Live Bait. S/F.....Ken M

I use a cheap stretch gauge and the torque wrench first on the bench cycling the bolts with the specified lube. Find out how many ft/lbs. it takes with YOUR torque wrench to get the stretch desired. Reapply lube and assemble noting "feel" of the wrench as you go to your predetermined torque setting. An A.R.P. or other quality bolt will be consistent enough to repeat throughout the set. The whole point is to stretch the bolt the specified amount whether it be by torque, lube wizardry,moon phase or a combination of all three.

Stretch gauges may be a pain to use on a motor, especially under the car in an emergency bearing check. But rod bolts are nothing more than a piece of steel with a given stretch rate that will repeat as long as it is never exceeded past a maximum value, which if I am not mistaken is about 33 percent more than the specs given. It is my understanding that rod bolts are just like springs, they will stretch, compress, or twist a certain amount for many cycles(sometimes millions) like they have to during use. Just goofing around in the shop one day I discovered I could stretch a rod bolt for my race rods by .0002 just with my finger tips. That to me proved the point that the spring or stretch rate is linear.
The stretch value puts them in tension at about 3/4 of their maximum strength so they have room to survive a long stressful life in the motor, yet still keep the rod caps together enough to not let the bearings distort too much or spin. I just don't see how a torque wrench can be consistently as accurate due to varying friction conditions.
Same goes for a torque plus twist method. It is more accurate than a torque wrench, but less than a stretch gauge IMHO.

Funny time for this post.

Just finished torqueing my Lentz Rods with CARR bolts. I was just going to use my micrometer. Snugged all the bolts up about 40 ft lbs. during assembly and mockup. Went back and loosened the bolts. Measured them and they were all over the map. Was ready to buy new bolts. Then found these bolts are not exact. So I wrote down each bolts length and was going to carry on. Just didn't seem to be a safe way to do it. So I bought a stretch gauge. The manufacturer showed .005-.007 stretch with no more than 58 lbs of torque. Well I did this for each bolt and found setting my wrench to 55 ft lbs was falling within these numbers. Not totally sure and never having a rod bolt failure in the past. I back each bolt off. Torqued each one to 40 ft lbs. then came back with a final torque to 55 ft lbs. This is the first set of steel rods in 20 years. And first all time with these small diameter shank 3/8 bolts.

If I design/build one of these engines new I don't suspect it will have steel rods or this tinker toy bolts.

GRP with 7/16 bolts and I feel I can't go wrong.

Leon

I have never used a bolt stretch gage in any of my engines, but want to learn more. It seems to me that if you torque the rod / bolts in a vice, then to stretch length before your final assembly the bolts would be some what stretched when unbolted and re torqued giving you a stretched bolt . Now would you stretch it again in the final engine assembly some more to the recommended stretch spec. or just torque to spec. ?