Date: Sat, 6 Nov 2004 11:41:56 -0600
Reply-To: Al and Sue Brase <albeeee@MCHSI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Al and Sue Brase <albeeee@MCHSI.COM>
Subject: Re: Torque wrench use
In-Reply-To: <5.2.0.9.2.20041106111025.00c35178@mail-hub.optonline.net>
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Well, If that is happening, I'd say there is some operator error. I was
very skeptical when I first saw the modern click type wrenches, even
more so of the ones from the Pacific rim.
Let me back up here. In 1965, when I was 16, and got my first real job,
working as a stock boy at a store downtown, I took my VERY first check
and walked across the street to Sears and picked up a shiny new
Craftsman bending beam torque wrench. (This shows you where MY values
were.) I still have it.
These bending beam torque wrenches were made by a company called
Sturtevant. together with the wrench came a nice handbook giving general
torque specs and some propaganda about their product. Basically they
said that if the beam had no damage and the pointer was centered, the
wrench would ALWAYS stay in spec.
I have no reason to disagree. I've taken care of it and its big and
little brothers and they all work just great.
EXCEPT, they are slow. And You have to be able to see the scale from a
perpendicular viewing point. Not always easy, especially when
RE-TORQUING water boxer heads.
I finally took the plunge about 5 years ago and bought a Husky from Home
Depot. Figured I'd give it a try and take it back if I didn't like it. I
like it. furthermore I compared it against my 3/8 drive Craftsman and
the torque is dead on.
I've built lots and lots of engines. Probably a few more American cast
iron anchors (a few very powerful anchors) than air cooled . But air-
cooled of all sorts, including lots of type 4's and type 1's, a few
Porsche 356 and 911 and even a couple of CORVAIRS!
I used to do the high performance small block chevys in 2 lb. steps as I
approached the spec. I sure wish I'd had one of these click type
wrenches back then when there were 34 bolts and 10 passes thru the pattern!
In using any torque wrench there are a few things to keep in mind:
1. You need to go slow enough to let the assembly move to its new
position. I read somewhere that over 50% of the torque applied goes to
friction at the interface of the bolt and the head. It is VERY important
that lube (or yellow sealer in the waterboxer) be applied to the
threads and nut face equally or some stud will not have equal tension.
Even after my wrench clicks there is some further movement in the
assembly. I just hold it there while the nut catches up. Not a long
time, maybe 1/2 to 2/3 of a second before releasing the handle. (They
don't BREAK, I do. They only move a vey small amount, maybe a degree or
two.
2. I use a few more steps than Bentley calls for. I can't remember
numbers right now, but maybe breaking down the last step into 3 steps,
more like about 2 ft lb. increments. You'd be surprised if you even
went through the pattern with the exact same setting. Usually the first
bolts in the pattern will pull down a little. Certainly no problem
going thru the last step twice.
3. I ALWAYS use the exact torque specs in the book. Unless on advice
from someone who knows more than the engineers at the factory. (In the
case of racers & high performance engines.) People who have taken a lot
of engines apart. especially engines that have failed! I've met a few
shade tree guys that thought the numbers in the book were just some
place to start from, maybe add 20 ft lb. to everything. DUH?
I am not an engineer, but I do have a bit of experience FEELING head
bolts move and indirectly from that feel, feeling head gaskets tighten/
crush.
4. This should have been #1, but it's important that any turning force
you make with the wrench be measured and only those forces. To do this
means you must put a very clean pull on the wrench and hold on to the
socket end with your other hand to keep it from being a bending force. I
nearly always use an extension. An never let any part of the beam hit
anything which would keep any of the measured force from being applied
to the fastener.
Al Brase
Tim Demarest wrote:
> As I've heard it described, it's because the studs are long, there is
> a certain amount of twist in them, so you need to *hold* the torque
> setting briefly. Since the 'break' type wrenches release immediately
> when the torque setting is reached, your heads end up under-torqued.
>
> Mind you, this is just what I've heard, I'm not an engine builder by
> trade.
>
> At 08:44 AM 11/6/2004 -0700, jimt wrote:
>
>> On 11/6/04 6:54 AM, "Vince Jahn" <vjahn4533@CHARTER.NET> wrote:
>>
>> > Hi All,
>> >
>> > I was just about ready to put my rebuild heads back on my 85 westy,
>> and was
>> > reading in the Bentley manual where it recommends not to use
>> > a "Break" type of torque wrench. Does anyone know why? I have
>> both, and
>> > would prefer using the "Break" type because I believe it's
>> > more accurate since I can dial in the 37 ft lbs.
>> >
>> > Thanks much,
>> >
>> > Vince
>> >
>
>
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