re-torque Pan-Heads

[chuck58pan]

does anyone have any special tools/tachniques for re-torque heads. I was given a # fo r kent-moore offset tool, only availavle through harley (Iimagine it is pricey) to be used w.a turned -down socket. it seem to me that a 3/8breaker would work. i have not as yet attempted to fit anything and i don't remember wha t i used to remove them. i guess if you had heat you could bend some square rod basically that is what the tool is minus the buttons to hold the socket fast. any thoughts? thanks, Chuck

[TimmyV]

here's what I used...http://www.mcmaster.com/#torque-wrench-adapters/=6ukcz3

[chuck58pan]

thanks Timmy v,for that. as uusual i have difficulty expressing my thought. it appears to me that getiing in at the head -bolts is going to be tight. I do need a torque=adapter though. Mc Master and I became close friends when i was going through the rolling=chasis assembly. nothig like needing something and finding it at your door the next day. thanks,
chuck

[Bill Golightly]

Don't forget to adjust the torque setting to compensate for the additional arm length.

[TimmyV]

If you keep the torque wrench at 90* to the adapter there is no difference in torque. If you have to use the torque wrench straight out, multiply the length (14" center to center in my case ) of the torque wrench by the length (2" center to center ) of the adapter & lessen the torque value by that much (28% in this case ). It is a tight fit on a Panhead but it can be done.

[Cotten]

TimmyV's tip is the key to torquing heads and cylinders in the chassis, with no math required.

No one adapter will reach everything, although a common obstruction wrench placed upon the torquewrench at 90 degrees reaches most of them. Two are shown at the bottom here:

torqtool.jpg

With a cheap torsion wrench that has a drive pointing up as well as down, the obstruction wrench can be applied in four different 90 degree positions, for working the handle around crashbars, etc. A 9/16" box-end usually fits the 1/2" square drive to allow the 5/8" end to be appliedt o cylinder base nuts, and a 5/8" allen socket allows the obstruction wrench to be reversed for 9/16" headbolts.

Reaching the base nut behind the timer usually requires some disassembly, unless you make a wrench to reach it:

CYLWRNCH.jpg

Accuracy of final torque spec is not nearly as important as getting them all even.

...Cotten

[awander]

If you have to use the torque wrench straight out, multiply the length (14" center to center in my case ) of the torque wrench by the length (2" center to center ) of the adapter & lessen the torque value by that much (28% in this case ).

Hi TimmyV, respectfully, I think your math is off.


Torque is the distance from the center of the rotation, multiplied by the amount of tangential force applied at that distance.

If you take a torque wrench that is 14" long, and you are reading, say, 140 in-lbs, that means you are applying 10 lbs of force to the handle.(140 in-lbs/14"=10lbs).

If you now increase the length of the wrench, by using a 2" adapter, to 16", the torque seen by the fastener(when the wrench reads 140 in-lbs) will be 10lbs * 16in, which equals 160 in-lbs.

To figure out how much to reducethe wrench reading by, you would need to divide the length of the torque wrench alone(14", in this example) by the length of the torque wrench + the length of the adapter(16" in this example), and multiply the desired actual torque by that number. That would be 14/16=7/8=0.875, so using the same numbers as above, if you wanted to torque the fastener to 140 in-lbs, you would look for a reading on the wrench of 140*0.875=122.5 in-lbs.

Checking the math, when the wrench reads 122.5 in-lbs, you will be applying 122.5in-lbs/14"=8.75 lbs of force atthe handle. Multiplying that by the actual length of teh torque arm, 16", gives us 8.75lbs*16in=140 in-lbs.


If I did it the way you described, I would instead take 28% off of the desired 140 in-lb torque, which would give me 0.72*140in-lbs=100.8in-lbs wrench reading. That would mean that I was applying 100.8in-lbs/14"=7.2lb of force at the wrench handle. Multiplying the 7.2lb force by the 16" length would give only 7.2lb*16"=115.2 in-lbs. This figure is about 17% too low.


Now, I won;t argue that it is important to have teh exact torque sopecs, or even that my torque wrench is more accurate than that. I don;t really know those answers, but I do think that we should be calculating things correctly, and also understanding why they are calculated that way.

[chuck58pan]

Cotten, handsome set of wrenches,adds credence to the old saying "necessity is the Mother of invention". Andy " what i'm sayin " is i'll have to read your example many times over to get it and i only have some wacky inch pound torque wrench: i had anticipated just feeling them all tight but less then sqeaky-tight .seeing those bends sets me of on another quest for an oxy/acetilene set-up. as alway's this group is the best intentioned, most well informed group that anyone aspiring to own and maintain these classics could hope for. thanks again, Chuck

[Cotten]

There's an easy way to avoid all mathematical errors, folks.

Like TimmyV said before he made it complicated,
Wrenches put together to make a right angle don't change the torque reading.

And a degree or two, plus flex of the extension, aren't really significant. The benefit of getting them all equal, and avoiding callous overtorques, far outweighs the accuracy difference between a Harbor Freight torsion wrench and a mega-bucks Snap-on glory stick.

Straight extensions have limited range of application, thus apparently require a calculator to get on different headbolts when working with the motor in the chassis.
The double-bend obstruction wrenches are not only more applicable,
they are cheaper!

headtorq.jpg

....Cotten
PS: For those who must consider angled adapters, please remember:
Connected wrenches that form an obtuse angle multiply the reading;
acute angles divide the reading.

That's why ninety degrees is zero change.

[beets]

here's what I used...http://www.mcmaster.com/#torque-wrench-adapters/=6ukcz3

Snap-on also makes one like this for double the price.