Valve Stem Protrusion; Knucks, Pans, and Shovels

Harleys are very rebuildable, and I would go so far as to venture that they may be among the most commonly rebuilt (using the term "rebuilt"somewhat loosely) of any engine family in existence. Such a supposition is somewhat bold, given the minuscule number of Harleys compared to the vast oceans of, say, small block Chevys. But face it, which engine is more likely to wind up in a scrap yard when it is in need of major repair?

Given that, along with the often less than spectacular life span of a top end rebuild on Knuckles, Pans, Shovels and Sportsters, many if not most have seen multiple valve jobs over the decades. Naturally with each valve job performed, the valves will seat a little deeper in the head. The method of gauging how much deeper is via the valve stem protrusion specification. Valve stem protrusion is one of those specs that is sometimes overlooked and to some extent misunderstood when dealing with Harley heads.

At issue are a several things. In no particular order; valve spring installed height, shrouding of the valve in the chamber, compression ratio, and finally rocker arm geometry. Having less than the minimum can lead to the devastating result of your valve springs reaching coil bind while your cam is still trying to lift the valves higher. Not a good situation and can usually be summed up as 'broken parts."  On the opposite end of the spectrum is the Panhead that looks as though the pan covers have been bashed out with a ball peen hammer (because they have indeed been bashed out with a ball peen hammer) so that the valve spring collars would not hit them.

Shrouding of the valve in the chamber from the valve being too deep is fairly easily remedied by a judicious modification of the chamber during the process of a valve job, though this too can overdone resulting in issues down the road when new seats are installed.  Along with deep valve seats comes a reduction in compression ratio (aggravated via de-shrouding) by making the chamber larger.  That may or may not be an issue depending on a number of factors.

Valve train geometry is also at issue, but I will attempt to address that later in the post.

To examine this subject I would like to start in the middle and work our way forward in time before going back to the beginning - that beginning being the Knucklehead.

On page 75 of the Harley Davidson Panhead Service Manual - 1948-1957 Rigid, we find what seems to be first official mention of the specification (at least that I can find).

The spec, which the drawing refers to as "Valve Seat Tolerance" is pretty self explanatory. It is the distance from the tip of the valve stem to top surface of the collar of the valve guide. The illustration also shows a gauge which was available for those lacking precise measuring tools or for quick checks. The gauge is simply a cylinder that straddles the guide. The "step" at the top of the gauge indicates minimum and maximum height; if the tip of the stem falls between the top and bottom of the notch, the stem protrusion is within spec.

The 1978-1/2 to 1984 FL/FX 1200/1340 4 Speed Service Manual (note the title may not be growing in length but it certainly is in use of numbers) shows the same illustration (page 3-18) for 1979 and earlier, but it might be worth noting that it offers a different illustration and spec for 1980 and later.

The difference, at least in part, is due to the changeover to valve guide seals. Earlier heads, both Pan and Shovel, only required a machined pad that was at least the diameter of the valve guide collar to locate the guide since the lower spring collar rested on the collar of the guide. The addition of seals made it necessary to rest the lower spring collar directly on the head to provide room for the seal, so the machined portion of the spring pocket was increased to the diameter of the lower spring collar.

Late vs Early

At first glance one might assume that the different spec is due to taking the measurement to a different surface, since it is now from the tip of the valve to the surface that the bottom of the guide collar seats against. And maybe that's the case, however, things don't seem to quite add up. If the collar on the guide is nominally .100" thick, then all is well. Add .100" to the early 1.500" to 1.545" spec and you come up with the '80 and later spec of 1.600 to 1.645". Ignoring the '80-'81 guides that used a .075" snap ring instead of having a guide with an integral collar, there is still the question of the gaskets that were under the guide collar on earlier motors. I had to look pretty close to even find the part number (18196-51) for this gasket in a Harley parts book since it does not appear in any later copies, though I have a small collection of them left over from top end kits. Measuring a random sample of these showed that they ranged in thickness from about .030" to .040". The James Gaskets catalog lists them as .031" thick with the application being 1951 to 1978.

Hmmm,... so with a window of only .045" in minimum and maximum stem protrusion, we find a variance of at least .030" just in whether or not a gasket was installed under the guide when rebuilding. And what about '48 to '50 Pans and '79 Shovels? Won't they show up as nearly at maximum protrusion right from the factory? And what does that mean when considering '80 and up which certainly never used the gasket? Now the .100" difference in stem protrusion spec doesn't add up so neatly because you have an "effective" guide collar thickness of .130" (collar + gasket) for many years.

Add all of this together and I think its safe to conclude that stem protrusion specification is probably not something will "make or break" your valve job unless you wander too far afield. My guess is that the spec was added after the fact as a guideline for mechanics rather than a part of the original design parameters of the Motor Company.

And if all doesn't throw enough margin of error into the equation, then consider this. If the Motor Company's stem protrusion specs theoretically provide correct valve train geometry (and that is a gigantic stretch given shops such as Baisley High Performance have presumably made a fair chunk of money over the years from their service of correcting Harley rocker arm geometry), then that still means that when you increase valve lift via a performance cam, you have also changed the stem protrusion numbers which should theoretically retain correct geometry.

Here is basically how it works. If you were to draw one imaginary line through your pushrod and another through the rocker arm's ball socket to the center of the rocker shaft, when your cam is at one half of its lift, the line should form a 90 degree angle. Likewise, an imaginary line from the center of the rocker shaft to the pad of the arm should also form a 90 degree angle with the centerline of the valve stem at that same half lift point. That way at zero lift the line through your rocker arm should be the same amount below 90 degrees as it is above 90 degrees at full lift. But that means that if you increase the lift of the valve with no other changes, then the angle with the valve closed will remain the same , but the 90 degree relationship between pushrod and rocker will no longer be at 1/2 lift. To get back to the theoretically correct valve train geometry you would need to lengthen the valve by an amount equal to 1/2 the increase in lift. Or, you could get the same effect by sinking the valve that amount. And guess which is easier and more cost effective, sinking the valve or having a custom valve manufactured?

All of that is to say that with a performance cam, the theoretically correct stem protrusion increases at a rate of half the increase in valve lift. In practice this also has the added benefit on a Harley of providing the increased valve to valve clearance during overlap (commonly referred to as Top Dead Center lift) which is needed for those performance cams.

Now, with all that to digest, I'll pause briefly before continuing with the question of valve stem protrusion on a Knucklehead.  Stay tuned.

Shovelheads Again

Unfortunately I was unable to get pictures to load for this post -  sorry - that would have made it much easier to follow and understand the material presented here.


It is not uncommon for me to receive a question in the comments section of my blog posts.  Sometimes it is an easy answer, but other times it requires a little more... and that may lead to a whole new post.  Such is the case here.  I recently  received the following in the comments section  of an older post:


 I'm interested in building a big bore shovel and have toyed with some do it yourself porting...there's some interesting views from the nightrider web site: How to Build a High Performance Shovelhead Engine.  I don't have a flow bench so was contemplating just smoothing out intake harsh edges and general polishing in lieu of redesign? Appreciate your thoughts if you care to comment...




First of all, a thank you to Dave for asking a very good question.  Probably most wrenches who worked in a dealership in the 1980's or before will recognize the sheets copied on the nightrider site.  I don't remember if they handed them out at the factory service school when I attended, or if my set was passed down to me from a previous attendee.  Either way, this info has been out there for a long, long time.  For reader's convenience I scanned my copies and attempted to place them her in the text, but to no avail.  Apparently the man behind the curtain at "Blogger" is too busy conquering the world to keep the picture uploading feature working at the moment. 







The material on shaping the intake ports presented therein (figures 5 and 6 in the link) has probably been the basis for a number of porting jobs.  However, before you drag out your TIG welder, consider this: if executed properly, this modification will indeed increase performance by way of greater flow.  Executed poorly, however the port modifications described can result in a net loss of performance. 






Unfortunately the difference between well executed and poorly executed can be very difficult to ascertain without the aid of a flow bench.  The reason is that the modification to the floor of the port leading to the valve seat (commonly called the short side radius) is one of the areas of a port that has the most potential for gain in airflow, but is also the most sensitive to shape.  The fact is, this area is one of the worst features of a stock Shovel head casting and also the most difficult to "fix."  It cannot be optimized by grinding; the problem is there is already not enough material there.  What is really needed is more material - just like this old performance paper suggests.








Stop!  I already warned you to hold up on dragging out the welder!  If you are going to start welding, you also may want to consider this; you will also need the ability to machine your heads for new valve seats.  Here is the reason.  If you look at Figure 6 in the link, you  will notice a dimension labeled 1.64 DIA. This smaller dimension just under the valve seat is commonly called the "choke" or venturi.  Let's stick with calling it the choke since there is also a similar situation in your carburetor also called a venturi.  And just to keep things on the up and up, I should mention that in porting discussions another choke is often mentioned, that being the place in the port that has the smallest cross sectional area other than the one just below the valve seat.  Of course that leads me to feel the need to point out that there is a 3rd item in the intake tract called a choke, which of course is in the carb and used for starting.  You can completely ignore that one!  So to sum up, there are 3 chokes and 2 venturi, but the only ones we are concerned with for this discussion are in the head.




This choke dimension (the one just under the valve seat - remember?), or more precisely the relationship of this dimension to the valve head diameter,  has an important relationship to airflow past the valve.  Now the nominal head diameter of a Shovel intake valve is 1.937 (1-15/16) often referred to as 1.94.  The 1.64 dimension means that this modification is calling for the choke to be just less than 85% of the valve size.  While it is easy enough to see where this 85% figure came from, putting my stamp of approval on it is a little harder.  The early SuperFlow  flow bench instruction books show a diagram of the ideal intake port area and shape and show the 85% relationship.  The key word there is ideal.  The only less ideal port shape than the Shovelhead which comes to mind are the tortuous switchbacks in the Knuckle/Pan intake tract.




Be that as it may, if you were to take your ordinary everyday Shovel head and measure the inner diameter of the valve seat insert, you may be surprised (or not) to find a number like 1.820".  Now if you do a little reverse engineering you will find that gives a choke percentage of almost 94% (1.820 divided by 1.937).   Now 94% is a far cry from 85%, but it gets worse (at least form the 85% perspective).  When  you were measuring intake seat insert, did you notice that it  that it really didn't line up with the aluminum of the port very well?  You aren't that observant?  Go back and look.  I'll wait....




Okay, visualizing the direction the mixture must travel, what do you think all of those 90 degree corners will do for your air flow?  What do you mean you left the head out in the shop?




So what you could do is remove the valve seat inserts, weld in all the areas shown in the drawing (and you may as well do something with the equally offensive exhaust port while you are at it) machine for new seats that have both a larger outer diameter and a smaller inner diameter, grind the port to match the diagram and do a valve job.  Piece of cake, right?  Oh... and before you decide to take a shortcut using some sort of porting epoxy, don't even consider leaving it hanging out over the seat insert as shown in the diagram.  It's life expectancy in an air cooled engine on the street will be far less than you like.





But, that is not to say there is no hope for you do-it-yourselfers.  First of all let's go back to that 85% choke figure.  It's probably a decent ratio for an exhaust valve, and maybe even for the situation in the diagram, but are you really going to spend the time and money trying to duplicate it?  Many, if not most cylinder head porters will tell you (if they are willing to tell you anything) that a good rule of thumb is to make the choke 90% of the intake valve diameter.  I have heard some of the very best say that you may sometimes need to go as high as 91% but absolutely no higher.  At least part of the reason is easy enough to visualized.  Air likes to turn in maximum increments of 15 degrees (which explains the angles used on a valve job) but it needs a little length for each of those angles - about .060" is enough.  But on a stock shovel seat insert with its I.D. at 94% of the valve, how much room is left on the inside for a 60 degree once the 45 degree angle is cut (or ground)?  Little to none, that's how much; and forget about adding a 75 degree angle.  Not much help in turning that air!




It is often said that one of the biggest factors in performance is the valve job.  But for the reasons stated above, I say: "Not on a stock Shovel!" On a stock Shovel about all the valve job can do is make a seal.  Sadly there is no material present to put good valve job on to help get that air turned.  Want to change that?  Put in a 2 inch intake valve.




Simple as it is, it improves several things.  First of all, suddenly there is enough meat left in the seat insert to add a couple more angles under the 45 degree seat.  Now your valve job can be a little more conducive to flow that the simple on/off spigot it was before.  Plus, now your choke percentage is a far more reasonable 91%.
 


As to the actual valve job, if you remember the 15 degree airflow rule of thumb, it becomes fairly obvious.  Just make sure that the outer edge of your 45 degree seat coincides with the outer edge of your valve.  That will leave the maximum room below that 45 for your 60 degree, 75 degree, and in the unlikely event that the I.D. of your seat insert is too small, a 90 degree.



Once you have an actual performance valve job in place, Dave's instinct to just smooth out the harsh edges is about right.  The turn that the floor of the port makes just before the valve (called the short side or short turn radius) is always a major offender on Shovel heads.  If the seat insert does not line up with the aluminum of the port in this area, don't be afraid to do a little grinding on said insert as part of putting a radius on this turn.  If you are more ambitious, get yourself a set of inside calipers and work at keeping the cross sectional area constant from the port opening to the short side radius.  And don't forget, if you want both heads to flow the same amount, you will want that cross section constant from front head to rear head also.




Finally, one disclaimer:  You don't get something for nothing. A 2 inch intake valve is heavier than a 1.94.  If your valve springs were marginal before, they are even less likely to provide good valve control with a heavier valve.  That's not too hard or expensive to take care of.  A bigger concern may be valve to valve clearance.  All things being equal, a .060" larger intake valve will be .030" closer to the exhaust valve when they pass each other during overlap.  The hotter the cam you have, the more likely that you will have issues.  If you decide to go with 2 inch intakes, you should check this whether it be via a full blown mock up on the engine or a bench check using the TDC lifts listed for your cam.


Of course that brings up at least one more question.  Is it possible to get a good flowing Shovel intake port without going to a 2 inch intake?  The answer is that you most definitely can.  With the aid of a flow bench many (myself included) have been doing it for many years.  But to do so one needs to make up for that poor seat shape somewhere, and that "somewhere" is most easily found via a flow bench.

Shovelhead Hydraulics

Now, now, now ...those are not swear words, though many mechanic has used them in a tone that would imply that they are.

Introduced in 1953 to replace the ill fated Panhead "hydraulic in the top of the pushrod",  certainly the 17920-53A was an big improvement since in 30+ years of wrenching I have yet to see its predecessor in working condition.  I did actually meet a man once who claimed that he had a working set in his motor, but I could not verify that he was not either deaf or a liar.  But I digress...

So, what is the first thing to do when you find yourself with noisy hydraulic lifters?  Adjust them of course.  And if that doesn't work, you adjust them again ....and yet again.  After one finally realizes that further adjustment is little more than wishful thinking bordering on the vain repetition of the prayers of the heathen, then what?

Now, we have all seen Shovelhead hydraulic lifters that function flawlessly; quiet and trouble free.  Common sense would tell us that for the most part this would be the norm, after all, the factory used them for over 30 years.  Somehow, though, it is the ones that are noisy that stick in our memory.  To be fair, a number of those that seem to be problematic are not to blame themselves, but take on the role of scape goat for other engine parts. 

Low oil pressure is the first logical root cause to examine before condemning the hydraulic unit.  Most who have been around Shovelheads for any time know to keep an eye on the tappet screen, since all the oil to the lifters must pass through it (hence its name).  Debris plugging this small screen can definitely make for some noisy hydraulics, though the type of debris and the amount of time it took to accumulate may also indicate larger problems.  Remember, the tappet screen is downstream from the gauge or sender, so you could have a good oil pressure reading, but still not enough pressure at the lifter. 

The oil pump itself could also be the culprit, but there again, excess wear could itself be a symptom of worn out parts serving up a metallic oil soup.   And then there are the bushings....  Oil pressure will seek the easiest path to relieve itself.  Fortunately there are only a few bushings in a Shovelhead motor that are subject to pressure, those being the pinion bushing and the rocker bushings.  Now  lifter noise in later Shovels with the multi stage oil pumps should not be affected much by loose clearance between the pinion shaft and bushing, since the pump is designed such that it must build pressure against the top end (hydraulic lifters and rocker arms) before the pressure relief valve opens enough to supply oil to the bottom end via the pinion bushing.  However, badly worn rocker bushings could still bleed off enough pressure to effectively disable the hydraulic lifters. 

But what if you have good oil pressure, the rest of your engine is in good shape, and you still have noisy hydraulics?  Well, maybe it's time to revisit that adjustment one last time.

First of all, I prefer to bring the engine to TDC on the compression stroke for one cylinder, and adjust both lifters for that cylinder at that point.  I'll assume you can find that place in your engine's rotation.  At that point the '59 to '69 FL/FLH-1200 Service Manual tells us to loosen (shorten) the pushrod until we have noticeable shake, and then extend it again until the shake is just taken up (just before it starts to compress the hydraulic unit).  From that point we are to extend the pushrod 4 full turns.  Fine.  I have use that adjustment many, many times with good results.

Now lets look at the '70 to Early '78 FL/FLH/FX/FXE/FXS-1200 Manual.  Here we find two methods.  One, called the "wet" method is identical to the one we just described from the '59-'69 Manual.  The other, called the "dry" method involves removing the hydraulics from the lifter, pulling the two halves apart, and cleaning out the oil (best accomplished with some spray brake parts cleaner or the equivalent).  With the hydraulics cleaned of oil, we are instructed to extend the pushrod past the point where the shake is removed and all the way until the hydraulic unit is bottomed out.  At this point, extending the pushrod length any further would begin to lift the valve.  Here we are instructed to shorten the pushrod by exactly 1-3/4 turns.  Again, I have used that adjustment many, many times with good results.

On to the '78-1/2 to '84 1200/1340cc 4 Speed Manual.  Here we find the old tried and true "wet" method to be missing in action.  And if that is not enough, the dry method has changed just enough to be barely noticeable (I just noticed it this summer after 30 years of valve adjustments).  Now we are to follow the same procedure as the "dry" method from the '70-'78 Manual, but instead of 1-3/4 turns up from the hydraulic being bottomed out, now it calls out 1-1/2 turns.  Hmm.  Do I need to say it?  Certainly I have used this adjustment many, many times (depending on which manual I grabbed) with good results.

But here is the interesting thing: for years I assumed that 4 turns down on a wet lifter would result in the exact same adjustment as 1-1/2 (or 1-3/4) turns up on a dry lifter.  It does not!  In fact, if it were not the for the 1-1/2 vs 1-3/4 discrepancy, I may have never realized this.  As it turns out, it takes about 8 full turns to collapse a Shovel hydraulic from its "wet" starting point to its "dry" starting point.  That means that using the "wet' adjustment method results in a hydraulic that is 4 turns up from bottomed out rather than the 1-1/2 or 1-3/4 turn up from the dry method. 

[2018 Update: If the range of adjustments listed above are not enough to convince you of the relative lack of importance as to the "exact" point in the lifter's travel, I have to add one more to the list.  While researching a totally unrelated issue I ran across this in Harley's "Shop Dope" publication from February 16, 1953.  This gives the recommended adjustment as 5 full turns down on a wet lifter.  If I count correctly, that comes to a total of four different factory settings for that lifter!]

Obviously  the wet method is much less time consuming if you have no other reason to completely remove the hydraulic units from the engine, but it looks as though extending the pushrods 8-1/4 to 8-1/2 might be in order (assuming the factory had good reason to go to a tighter adjustment in later years).  But it also becomes obvious that precise adjustment is not critical if all else is as it should be.  So next time you adjust your lifters don't sweat it if your wrench slips and you think you may have gotten a half turn off.  If its still noisy, better to spend your time investigating whether it is an engine problem or just bad lifters.

Measuring Compression Ratios

Have you ever considered what the actual compression ratio of your motor is? Are you sure that you took everything in to account or are you going by the rated compression ratio of your pistons?

The simplest way to measure the actual compression ratio of your engine is to have it assembled, at TDC, and then "oil out" (old school term for measuring the volume) the combustion chamber. But to do this you must also be able to position the engine so that the spark plug hole is at the very top of the chamber so that you don't get an air bubble trapped which would throw off the measurement. Pretty awkward to say the least!

Every other method involves measuring separate components and calculating the ratio mathematically. Here are a couple of things to consider when doing so.

• cc of a cylinder = diameter x diameter x 12.87 x height

This formula is especially handy for an old time Harley guy like me since you enter the specs in inches, and the constant (12.87) converts the answer to cubic centimeters.

• Head Volume

The normal way to cc a Shovel, Pan or Knuck head is to place a piece of Plexiglas with a small fill hole across the gasket surface. When you do this you will be measuring not only the chamber, but also the space into which the fire ring on the cylinder fits. That means that the volume that the fire ring displaces must be calculated and subtracted from the head volume. Treat the fire ring as a cylinder and use the formula above. To get the cc's of the fire ring it is only necessary to calculate once using the o.d. of the fire ring and then subtract the volume found using the i.d.

• Gasket thickness & gasket bore diameter

Think of it like another really short cylinder and use the above formula to compute the volume.

• Piston deck height

If your piston only comes within .010 of the top of the cylinder, it is just like running a .010 thicker gasket.

• Piston dome volume

This can often be found in manufacturers specs, but not always. You can grease the piston rings, install the piston into the cylinder so that the top of the dome is just below the cylinder top, and then measure the distance down to the deck of the piston. This will serve as the height inserted into our magic formula above, which allows you to use the bore diameter to compute the volume of the cylinder formed from the piston deck to the top (if it did not have a dome in it). Once you have that volume you can oil it out and subtract to get the dome volume.

• Valve stem protrusion

How far the valves were sunk into the heads from previous valve jobs. Now, if you just finished oiling out your heads, this is of no consequence in computing your actual compression ratio. But it will help explain why your compression ratio is not as high as your piston manufacturer claims. Low and behold our handy dandy little formula comes to the rescue again. If you use the valve diameter in the formula along with the amount that the valve is sunk deeper than the minimum spec as the height, you might be surprised how much compression ratio you loose.

[as an example, stock size valves in a Shovelhead when sunk .050" will increase the combustion chamber size by 4.39cc, lowering the compression ratio by about 1/3 of a point]

This is especially relevant on the older motors which usually have a lot of valve stem protrusion and the valve un-shrouding which often accompanies it. In performance applications, the valves often have to be sunk to maintain valve to valve clearance with the hotter cams that are available, so that is also something to take into account when selecting your cam and pistons.

Now perhaps you think all of this doesn't much matter on your average cruiser. Well, maybe. On the other hand, keep in mind that higher compression ratios make a more efficient engine, and thus better fuel economy and power. On the other hand too high a ratio can lead to hard starting and worse yet, pinging. Another consideration is that all cams have a compression ratio range that they will work the best in.

Book of Shame

This will be a bit of a rant, I am afraid.

About a week ago I decided to start keeping a record of parts made for Harley Davidson motorcycles that don't fit, don't work and or are just plain shoddy. Believe me (and I am sure you do if you have ever worked on Harleys for a living) this is a constant, ongoing problem in this business. Lately I have had an absolute rash of junk parts to deal with.

I have dedicated a 3 ring binder to this purpose and intend to keep a record of every part I come across that is manufactured incorrectly with the part number, application and manufacturer of the "junk part."

It was really easy to fill up about 3 pages without going very far back in time. I am sure more of the parts I have "beat my head against the wall" about over the years will come to mind and be added as time goes on.

Yesterday I had a four new entries for the book which cost me about a half a day of labor. These were parts that I paid good money for, which were incorrectly manufactured. And this was all just in one section of one motor. Usually the problem does not become evident until you are in the middle of an operation. Did I mention how frustrating this can be? Then to top it off, there are always the added problems. How many hoops will I have to jump through to return the part? Is every one of this particular part from this manufacturer defective? Is there any other source for the part? Can I make the part work with modification? How much time will I waste trying to get any kind of answer from the manufacturer? Does the manufacturer care even a little bit that they are selling junk?

Yeah, a bit of a rant, but you should hear me when the circumstances are fresh. By the way, I titled the 3 ring binder "Book of Shame"

Shovel Head Gasket Tip

Since I have been on the subject of Shovelheads lately (drag racing stories) it came into my mind to give a tip on torquing Shovel head bolts. This is a trick that was taught to me by Dick Conger over 25 years ago while I was working for him in his Harley dealership in Pueblo Colorado. If you are sharp you may note that is somewhat similar to the factory torquing sequence for Evolution head bolts, but Dick taught me this before the Evolution was even born!

I say that it is similar to the evolution torque pattern, in that it tightens down on each side of the oil drain hole first and then goes to the opposite side. The idea is to put a good tight squeeze on the drain hole first, since that is generally the source of head gasket failures on a Shovel. Of course it is far different from the Evolution sequence in respect to torque steps, as the Evo sequence is more concerned with cylinder distortion.

A little lube on the threads as well as under the head of the bolt will help keep your torque readings accurate. And don't forget, you also want to reach the torque setting of your wrench while it is still moving, because it takes more torque to start a bolt moving than it does to turn it. For that reason it helps to plan ahead so that you don't run out of room to "swing" your torque wrench just before you reach the full torque reading.

I know some will say that you don't need a torque wrench for Shovel headbolts. I even talked to a tech at S&S recently (who will remain nameless) that said he doesn't use one for Shovelheads. My only answer would be, that of the thousand or so Shovel engines I have torqued using this method, the failure rate has been zero, or very close to it. Happy wrenching!