If it's not true it should be. Here's a link about stretch I
just found: http://www.arp-bolts.com/pages/tech/fastener.html
-----Original Message-----
From: elliottd [mailto:elliottd@look.ca]
Sent: Tuesday, February 11, 2003 1:51 PM
To: Bill Babcock; FOT@autox.team.net
Subject: Re: Retorquing head gaskets
If you remove all the split lock washers, you must be removing about 5
pounds. That will increase your acceleration.
I heard somewhere that Colin Chapman fired a mechanic for using washers on
their Lotus 7's or 11's because of the added weight.
Don Elliott, 1958 TR3A, Montreal, Canada
----- Original Message -----
From: "Bill Babcock" <BillB@bnj.com>
To: <FOT@autox.team.net>
Sent: Tuesday, February 11, 2003 4:08 PM
Subject: RE: Retorquing head gaskets
> By the way, here's some common stretch specs for ARP bolts, along with
> a little more discussion on torque VS stretch from a website I found.
> The angle method scares the heck out of me--I don't know why. It feels
> like "tighten it down till it breaks and back off half a turn". I
> don't remember the URL, I saved it as text in my Triumph resource
> file:
>
> For any fastener to supply clamp loads high enough to keep the parts
> bolted together, it must be stretched the proper amount. Torque does
> not measure bolt stretch, it measures friction. This is why we prefer
> the stretch method or the torque and angle method for tightening rod
> bolts.
>
> To use the stretch method, measure and note the free length of each
> bolt before tightening with a stretch gauge or a micrometer with ball
> end attachments. Then, using the chart below, tighten the bolt until
> the proper stretch is achieved.
>
> The torque and angle method uses the lead of the thread to stretch the
> bolt the proper amount. To use this method, simply torque the bolts
> the amount listed in the chart below (this low amount of torque snugs
> up the bolt and removes lash). Then, using a Snap-On #TA360 torque
> angle gauge, turn the bolt the listed number of degrees.
>
> Bolt Type Recommended Stretch Torque & Angle
> 5/16 - Oliver/ARP 3.5 .0052" to .0057" 10 ft lbs + 55 deg
> 3/8 - Oliver/ARP 2000 .0052" to .0057" 25 ft lbs + 50 deg
> 3/8 - Oliver/ARP 3.5 .0057" to .0061" 25 ft lbs + 55 deg
> 7/16 - Oliver/ARP STD (Black Bolt) .0048" to .0055" 30 ft lbs + 40 deg
> 7/16 - Oliver/ARP WSB .0053" to .0058" 30 ft lbs + 40 deg 7/16 -
> Oliver/ARP 3.5 .0060" to .0065" 30 ft lbs + 50 deg
>
> As a final check to make sure no bolts were missed: Before bolting the
> oil pan on, set a torque wrench at 50 ft lbs (use a wrench set at 30
> ft lbs for 5/16" bolts), and check all rod bolts. If any bolt turns
> before reaching the preset torque, it has not been properly tightened.
> You must loosen these bolts and tighten them properly.
>
>
> -----Original Message-----
> From: Bill Babcock
> Sent: Tuesday, February 11, 2003 10:39 AM
> To: 'John Wilkins'; FOT@autox.team.net
> Subject: RE: Retorquing head gaskets
>
>
> I think everyone is on the right track. The complicating factor is how
> much everything moves. These are very strange engines. We have a cast
> iron block, steel sleeves, cast iron head, some very long and
> relatively short bolts, none of which are through-bolts. All these
> things are heated differently and cooled differently. Then we have a
> wide array of gaskets--composition, copper clad, steel clad, steel
> shim, steel shim with copper wire, and solid copper.
>
> One answer for all? I doubt it.
>
> I always retorque the heads--why wouldn't you? I'm not that committed
> a spectator, so I tend to fuss around my car in the pits. If I set the
> valves I usually torque the heads first. Every so often you find a
> bolt that has loosened a little somehow. If you use either composite
> or shim steel with a copper ring, you'll see a substantial change
> after a heat cycle. Not just once--you see it six months later.
>
> A bigger question is are the bolts dry or lubricated. That's a much
> bigger variable than the heat cycle. If you torque a bolt to it's
> published spec dry the chances of pulling out the threads or breaking
> the bolt are very low. If you use a very effective (for sliding
> friction) lubricant then the same torque will rip out the threads or
> break the bolt. I got obsessive about this issue after I broke a long
> head bolt at the base of the thread way down inside the block in the
> pits before the Monterey Historics.
>
> Most torque specs assume a motor oil lubricated bolt. If you want to
> really do it right, you need to find the stretch specification for
> each bolt you are using, lubricate it with the lube you intend to use,
> put the bolt in a fixture that will allow you to measure stretch,
> torque it to the stretch spec and read the torque value. Then always
> use that lube with that bolt.
>
> With bigger or longer bolts, motor oil or dry torquing will give
> highly variable numbers when you torque to a stretch spec. The torque
> jumps as the bolt sticks and slips. The super slick stuff supplied
> with high quality bolts is too scary to use--on a cheap bolt you'll
> exceed stretch specs way before you see any significant torque.
>
> Gear oil works okay, but I've settled on a cheap, readily available
> anti-seize compound that I use for everything. I've also gotten
> allergic to split lockwashers. Spending any time investigating bolt
> torque and stretch will convince you they are a tool of Satan. Instead
> I have big bottles of every type of locktite. I'm gradually
> eliminating lockwashers from everything.
>
> For simplicity sake I torque the long and short head bolts the same,
> even though they really do require different torques to reach spec
> stretch. With a shim steel gasket and copper wire rings with
> anti-seize on the nuts and good, hard washers (no nicks on them
> either) 65 pounds is good. After a heat cycle I remove the nuts one at
> a time, re-lube lightly, and retorque to 65.
>
> So far, so good.
>
> Sounds like too much trouble, but it only took me a couple of nights
> to make a fixture and test the bolts (I just drilled lengthwise
> through a 2" thick chunk of steel I had, put a nut and locknut on the
> bottom end of the bolts, and borrowed a big micrometer to measure
> bottom to top of the bolt at five pound increments), and retorquing
> takes about an hour.
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