Saturday, March 12, 2011

Get torqued!!

Ok, this will be a bit lengthy, but will be well worth your time. Especially if you have the scars on your knuckles to prove that you wrench on Shovel and Pan engines in the frame. I've figured out a few tricks over the years that simplify the task of getting proper torque on the hard to reach head bolts which will help you get more life out of your head gaskets (which is probably why your heads were off in the first place). First off, I always wire brush the head bolts and chase the threaded holes in the head with a tap before assembly. This insures that I get full torque on the bolt and that some of my final torque is not being taken up by interference between the bolt and the head due to dirt or corrosion or damaged threads ect. After I've cleaned up the threads, I install the heads and new gaskets and run the bolts into the heads finger tight. I then install the intake with two piece clamps (no o-rings) to acheive proper alignment of the heads to the intake. This will allow a good seal when doing final installation of your intake and carburator. If you are still using stock type band clamps, throw them in the trash (the only place they dont produce intake leaks) and get a set of brass two piece clamps.

Here comes the fun part! See that crazy looking apparatus on the lift? Thats my torque wrench and an "S" shaped torque extension. Torque extensions are pretty straight forward to use. There is a formula that looks something like this:
(ELxT)/(EL+TE)=AT  Now dont freak out, thats not as tough as it looks. If i can figure this out, anyone can. Basically you have to adjust the torque to compensate for the added length of the torque extension. That's where the formula comes in. It breaks down like so, EL is the effective length of the torque wrench measured from the center of the drive to the center of the handle with the wrench set to your desired finished torque before adjustment. I was lookin for 65 ft lbs of torqe, so that's where I set the wrench. A quick measurement tells me that my "effective length" = 17.5". "T" represents torque. This is the full torque you're looking for before adjusting for the extension. As I said before, mine was 65 ft lbs. So the first part of our equasion is 17.5 x 65 = 1137.5

Next we need to add TE to our established EL. TE simply stands for torque extension. My "S" wrench (snap on PN SBXM1415) is 6.625" from center to center. Adding that to the 17.5" EL gives us a length of 24.125" for our wrench and extension. Ok, remember that 1137.5 number we came up with earlier? Divide that by the 24.125" and we have our new torque wrench setting with extension or "adjusted torque"; 47.15 ft lbs.
I usually drop the .15 and torque my heads to an even 47 ft lbs.

That fancy "S" wrench I'm using as a torque extension is actually a 14-15mm combination boxed end wrench. The 15mm end will fit nicely on the 1/2" drive of the torque wrench while the 14mm will fit nicely on the 9/16" hex on the head bolts.The nifty "S" shape is what allows easy access to the hard to reach areas that MR's Harley and Davidson decided to stuff nearly unreachable head bolts into! Also, as you are torquing the bolts, be sure to keep in a straight line the handle, drive unit, and center of the 14mm wrench. As in don't rotate the wrench way off to one side or the other as this will not yeild acurate torque results.

The great thing about this formula is it works with all different lengths of wrenches and extensions. Just do the math according to what you have. And the last thing i would encourage, is to write all this down in the margins of your workshop manual as to not forget it. Afterall, you ride a shovelhead. Chances are you will need this information again.


  1. easily one of the best write ups and tech Iv'e seen on this out there. Great Job.

  2. Thanks Dan! I really hope someone gets some use out of this stuff. Just tryin to do my part to keep these old bikes out of the shop and on the road where they belong!