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Re: A couple of engine rebuild questions

Subject: Re: A couple of engine rebuild questions
by rayquayle on 2011/1/27 1:42:08

Quote:

rklessdriver wrote:
Ray
I would HIGHLY suggest you measure the bolt stretch.

The tool from ARP or BHJ is only $150.00-$200.00 and is $$$ well spent.

I can guarentee that short 7/16 ARP 8740 bolt will not stretch the proper amount using a TQ wrench....

There is a good reason Scat changed those rods 2 years ago from 3/8th ARP 2000 bolts to the 7/16 bolt - because people were building oval track engine right on the 550HP power rating and using TQ wrenches.... Those rod bolts were breaking and scattering motors everywhere. The ARP 2000 bolt is VERY sensitive to proper stretch for proper clamp load.....

The 7/16 ARP 8740 bolt is more forgiving but I can tell you as short as it is.... I'd bet the TQ rating is 70-75 lbs....

I would like you to read this. It pretty well covers the peril of using TQ wrenches on a critical fastner like a high performance rod bolt.

http://www.campbellenterprises.com/co ... tretch-assembly-specs.php

I'll also offer my apologies for the thread drift and subsequent Hijack.
Will

OK Will, very good info. I actually have an ARP stretch gauge and intended to use it, but in the past I'd always had new bolts that I'd measure relaxed, right out of the box then torque to the specified stretch. I was unsure what to do with pre torqued bolts that come with new rods. I guess I didn't get what you were saying in the last post. Must've gotten distracted when you said anal!

So what I want to do is measure the length as they come from Scat torqued in the rod and then torque to the same length when I reassemble. Sound right? Thanks again for all the help.

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