Head bolt torque

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shaker
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Head bolt torque

#1

Post by shaker »

I have to put a head gasket on my 49 pan this winter got one that started leakin this summer , going to use the teflon fire ring , should i torque the old 54 year old heads to 65 ft lb, or maybe 50 ? what do ya thank. shaker.
Cotten
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Re: Head bolt torque

#2

Post by Cotten »

It's more important how you torque rather than to what figure you torque to, although I use 65 as well.
If you have a"clicker" wrench,.. break it in half and toss it as far as you can.
A cheapo dime-store torsion wrench is infinitely better.
The real problem is one of getting onto the bolt heads, particularly in the chassis after a few testrides. The solution is an "obstruction' wrench, which is a C-shaped double-opened end wrench available from most good suppliers, ( like http://www.mscindustrial.com/), and an adapter which is just a 5/8" Allen socket.

As long as any adapters to your wrench make a 90 degree angle, it does not change the reading appreciably. That's the trick.
And oh yeah,...ever decide why it leaked? Better grind it flat beore you install it. It is real common for the headbolt inserts to protrude from years of use.
And when you re-intstall, pressure test your intake manifold, as heat is the #1 reason for heads to warp in the first place. This makes the "fire-ring" gimmick as redundant as suspenders and a belt.

Good luck!
shaker
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Re: Head bolt torque

#3

Post by shaker »

thanks cotton, sounds like good advice i am haveing a local machine shop make me a truing plate out of a 1/2 " steel plate , going to put a pice of sand paper on it to find high spots on the heads, i have a pressure tester that i made from a old manafold extion , i saw the pic of one on indian web sight,, I was lucky that my bike still has the plumers, shaker.
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Re: Head bolt torque

#4

Post by VintageTwin »

Plumbers shaker, not plumers or plummers!
65 ft. lbs on the head bolts. Criss-cross. Sears (you can grind the Craftsman name off and write Snap-On with a tool marker, like I did. Nobody will pick up on it) makes a nice clicking torque wrench. Get three. One for 20 to 150 ft.lbs for the motor and trans sprocket, one for 10-75 ft.lbs. fer da head bolts, and da third one 25-250 inch lbs for the oil pump. A "quiver" of click wrenches. On those Pan heads..... The inserts get pulled out a little over the years from people re-torquing their heads without removing the gas tanks to loosen the top motor mount bolt from the frame. They pull the heads down and the head is fastened to the frame....somethings gotta give...and it does...them webbed in inserts in the head, that's what will "give". If you put your heads on a flat-plate and it has a measurable air gap when you run a feeler guage blade betwixt it, then have a machinist counter-sink only the inserts a tad. Do not remove aluminum material from the gasket surface. Look at the pictures of milling gone wrong in the Clymer Panhead manual. "Careful with that axe Eugene"- Robbie Roberson, The Band-1969Grinding heads to flat
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Re: Head bolt torque

#5

Post by Cotten »

I was lucky enough to get a freebie grinding stone that is 42" in diameter. I made a patio table out of it. I call it my "Polish Mill" because I run around it with a workpiece while it stays stationary. It quickly flats out the gasket surface without the rounding problem that benchtop swirling on a plate can cause,.. if you get impatient.

Meanwhile, if I had a clicker torquewrench, I'd weld it solid into a breaker bar. They never have a double drive, one up and one down, like cheapo torsion wrenches. The double drive is priceless when it comes to retorques in the chassis.
57stroker
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Re: Head bolt torque

#6

Post by 57stroker »

Before the local Snap-On dealer threw in the towel and went out of business, he showed me a new electronic torque wrench. It was only 3/8" drive, but it auto ranged from inch lbs. to 70 or so foot lbs. It buzzed your hand and beeped when it reached the torque setting. It then displayed the peak torque that was reached. It would time out, re-zero and shut its self down if you forgot to turn it off. It would torque in both directions if need be (SnapOn sells other "clickers" that will do this also) The price was only a little above the other over priced clickers they sell. (I'll wait for the import clone!) Sure was cool though
shaker
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Re: Head bolt torque

#7

Post by shaker »

I have one of those big grinding wheels, that my Dad left to me. I never thought of it, might give it a try, if my wife ain,t sold it at one of her stupid yard sales!! shaker
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Re: Head bolt torque

#8

Post by Andygears »

Years ago (many more than I would like to count) I attended aircraft school to pursue an airframe/power plant licence, and was taught very strongly that ALL clicker type torque wrenches must be recalibrated periodically. Think about the mechanism: a spring inside a bar, of known length? With a screw at the end to adjust the length, calibrated for an "average?" Spring rate at a given temperature. If any of these factors are off from: dropping, over tightening spring, cold or hot temp. ...on and on. Then the torque may be different.

Compare to a beam T-wrench: a fixed bar of known alloy has, in engineering terms, a known "Modulus of elasticity" that unless used as a hammer or otherwise dented will never change. The pointer affixed to the head will always stay straight and the scale is usually graduated smaller as the value becomes greater.

Probably don't matter for an old pan but striving for high accuracy should yield acceptable results.

Further, I agree with Cotton that bolt thread and hole thread should mate freely and smoothly before assembly otherwise torque values are meaningless. My two cents

Andygears
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