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.