GRP L19 Rod Bolt Stretch Process

I have a Hemi with GRP Rods: Question is what process do you use to tighten your rod bolts?

I use a torque wrench (changing the settings to achieve the .0075 stretch needed for my L-19 bolts)

I have been told that a torque/angle process also works? Torque to 30lbs then add 75 degrees of rotation.

Any thoughts?

 

I'll take a shot at this as no one has yet. My rods came with L-19's from GRP. They said stretch the first few bolts properly, then if you want to speed things up use a torque wrench to match the stretched torque. Just go a little less at the start. If its off, back the bolt all the way off and go up all in one pull. Biggest thing is to check all the fasteners with the stretch guage at the end, don't rely on the torque wrench.

I guess a torque angle guage would work but just run you stretch guage over all the bolts again. Biggest thing was torque had to be brought up all in one shot, and wear gloves when handling the bolts. Never let them touch bare hands oiled or not.

Corey

 

Did this and to me was a huge waste of time - switched to MGP and 20+ runs with no issues on each set. I have paid for them all, MGP is by far the best rod out there.

Brandon Booher
NHRA TAD #323
Torque MGMT. - Owner

 

We're ignorant / lazy or both and we still get away with just using the torque wrench, but I would have to agree that stretch is the only true measure of clamping force.

I was wondering though if anybody is using ultrasonic bolt stress tools. They seem to be used in industry for pipe flange bolts and coupling bolts and I can see it being an easy method for rod bolts as well.

Something like: http://www.norbar.com/Products/tabid/54/mid/1202/view/category/category_multid/8/Default.aspx

Any thoughts / experience?

 

I agree with Brandon on this .... It may be better but all I have ever used is arp's ultra Tourque lube and a very high quality non click type digital wrench, never had problem

 

Torque Angle Method

Leon,
For teams that are checking the rod bearings every run, as most Top Alcohol teams do when they are running hard, torquing the rod bolts to a set number with the same torque wrench and bolt lube works quite well. However, for teams who go multiple runs between checking the rod bearings, a more accurate method of verifying bolt stretch is extremely important. The best way is to use a rod bolt stretch gauge, zeroing it for each rod bolt. This is a difficult, time consuming process under the car with oil dripping on you, made even worse if you are checking bearings between runs when it is hot. We spent many hours on the bench with a rod vise, stretch gauge, and torque wrench to come up with a torque angle method that produces the desired .0075" +/- .0005" of stretch with L-19 bolts. By torquing the bolts to 30 ft-lbs, then an additional 75 degrees, we are able to reproduce extremely repeatable results (this is with our torque wrench, other wrenches should be verified for repeatable results). We use ARP's bolt lube, but we have also tested with other lubes. Different lubes do make a difference, but not as much as they do when torquing to a preset number. Torque is a measurement of friction, so lubes have a significant impact on your results. Angle is a given number of degrees of rotation, which will produce more consistent results due to the thread pitch being a mechanical factor, and not a measure of friction. This method takes a bit longer than simply torquing the rod bolts, but is much quicker than trying to measure bolt stretch laying under the car. Nor rod on the planet will live with one or more bolts laying in the pan. Hope this helps

 

Thank You!

Thanks to everyone for your input!!

Leon

 

I do bottom end on Stig Neergaards top fueler here in europe. In the shop and at the races.

We only use a torque wrench and engine oil. nothing else. We snug up the bolts with the air impact set on low and then use the torque wrench. At the start of all events we check all our torque wrenches, on the digital tester in the trailer.

One thing tho. The rods and rod bolts in a top fuel don't see the kind of rpm they do in a TAD or TAFC deal. I believe that the rods in a fuel car sees much more compression load, due to the power of nitro and the crazy advance needed to run on these engines. The rods in a TAFC and a TAD see much higher rpm which i believe puts a different kind of stress on the rods and bolts. I have no proof of this, it is just me thinking.

I do it excatly the same way on my own Top sportsman style door car. It has a TFX hemi. I have had plenty of problems with the car but none caused by loose or too thight rod bolts.

 

So when you guys check your rod bearings in the pits , what do you do with a warm rod when you retorque them ?