Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

Well i pulled my CP pistons out of my block because apparently they had a design flaw on the older ones on the intake valve relief, so i brought them down on the side.
Now my question..
Who uses a stretch guage when installing rod bolts and who uses a torque wrench?
I used the moly lube on the ARP 2000 3/8 rod bolts and torqued them to 43 ft lbs with my torque wrench but now i am having second thoughts on using a stretch guage...
What are your thoughts?

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

ARP Lube, and the spec for that lube


/

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

I torque em... ---- all that fancy ----.

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

Torquing them has worked fine for me. Call the manufacturer and they will tell you a torque spec for the bolt, good enough for me.

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

If you think about it measuring the torque relies on translating rotational force to the force stretching the bolt through the ramp of the bolt threads (holding force). Measuring the stretch of the bolt itself you can calculate the holding force of the bolt directly based on the strength of the steel. There is less room for error measuring the stretch of the bolt, but theoretically you can get the same place either way.

Just make sure to limit the error possible with measuring torque by cleaning the threads and using the recommended lube. Any type of extra friction from dirt and ---- will require more torque to twist the bolt falsely calculating your holding force higher than it is.

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

give them that last 'tat tat tat' from the impact to know youre good and torqued

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

tourqued down, and hit with a breaker bar a couple times for good measure, bling

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

When not using a stretch gauge arp recommends running through the torque sequence a few times with arp lube.

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

tthanis mr arp

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

not to thread jack but i just reinstalled some without the lube...how big of a problem could this cause? what should i do?

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

take them out and if you don't have the arp moly lube then atleast use some kind of moly lube

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

I used a stretch gauge.

They are like 40 bucks you cheap bastards.

:P

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

I'm pretty ---- about putting that ---- together, and I just use a torque wrench. but like jago said its very important to make sure the threads are super clean and a good coating of the correct lube applied. I use Gn moly paste which is basically arp lube.

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

what is the signifacance of the lube? just the more accurate torque reading?

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

I just assumed the lube acted to distribute the load evenly to the threads since liquids are incompressible (in general).

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

I just explained the lube above, to give an accurate and predictable amount of torque caused by friction of the screw turning.

when you turn a screw, some of the force you are putting on the threads (incline plane) are acting against friction, some of the force is translated into holding power. (remember high school trig clas sin cos tan anyone?) The less friction, the more force is translating into holding force and the more accurate and reproducable reading you will get.

Re: Builders: ARP 3/8 Stretch Guage vs. Torque wrench
 

Stretch gauge...

Sorry, but if you are that worried about getting the correct amount of fastener preload, then that is the most accurate way to measure it.