I'm relaxed, just got confused and wanted to ask.

 

I believe you are mistaken on this point. Could you explain?

It is my understanding and experience (cars, not necessarily HD's, but the same principles apply) that while a loose adjustment may cause a little more noise, there is no way it could ever cause valve float. On the other hand, if the adjustment is too tight, in a worst case scenario the valve may never completely seat and that is definitely more harmful than a little noise.

Please tell me where I'm going wrong.

Thanks.

 

Regardless of how many turns, we load the lifter, .140"-.150".
Never an issue.
Scott

 

Whew, I was staying totally out of this because the numbers being thrown around were different than all the research I've done these past 8 months on this subject.

Scott just confirmed why my numbers were not adding up.....so to speak.

The information I discovered matched Scott's regarding preload. That typical preload it is more than the .100 previously stated. Its more like .140 -.150.

When I do the math for an SE set of push rods that have 24 tpi, you come up with the following.

At 24 tpi, each thread is .04167 (rounded) of an inch; divided into 0.145 preload (mid-value from Scott's post), you get 3.479 turns.

As already been said, the number of turns though, will be different if the push rod's thread count per inch is different. Do the math.

Jim

 

There is a lot of confusion going on in this thread about lifter preload. I’m going to express my opinions. This may provide clarity for some, but also, more confusion for others. Let me also state that most of my experience comes from the automotive field, and not necessarily Harleys in particular, but hydraulic lifter function is the same whether it’s a Chevy, a Ford, a Pontiac, or a Harley.

First you have to understand the basic theory of how a hydraulic lifters functions. A hydraulic lifter uses the engine’s oil pressure to fill the cavity within the lifter. As the lifter cavity is filled, the lifter plunger rises in its bore to the point that all lash or clearance is eliminated from the valve train. Since oil is non-compressible the hydraulic lifter is essentially solid at this point – except for the bleed rate engineered into the lifter design. In the simplest of terms this is how a hydraulic lifter functions.

Next is the hydraulic lifter adjustment. In order for the lifter to perform properly and maintain zero lash in the valve train, the plunger must be set within its range of travel. This is where the term lifter “preload” comes into play. With the lifter on the cams’ base circle, adjustments are made to eliminate all lash from the valve train, and then further adjusted to compress, or preload, the plunger into the lifter body bore. On a Harley this is most often done by the use of adjustable push-rods.

Here is where my opinion comes into play. Theoretically, as long as the lifter plunger is preloaded “somewhere” within its range of travel, and it does not bottom in its bore or extend fully to its retaining clip in operation, the lifter performance, including noise, should be equal. In Harley terms, whether you preload the lifter one, two, three or four turns of the pushrod, or .040, .080, .120, or .160, it should have no bearing on performance providing the lifter is functioning properly.

Even though absolute value of the preload is not that critical in my opinion, setting the plunger near its midpoint of travel provides the most flexibility and service life and this is what I’d shoot for.

But there can be arguments made for adjusting the preload intentionally “tight” or “loose”.

If lifter pump-up at high RPM is a concern, a looser setting may be desirable. Less than adequate valve spring pressure can also contribute to lifter pump-up. Lifter pump-up can have catastrophic results such as valve to piston interference or burnt valves from holding the valve open off its seat and overheating the valve. This is the reason in an earlier post I suggested it safer to err on the side of a little loose if there is any question at all in the adjustment specification.

On the other hand, a tighter setting may be desirable if absolute maximum valve lift and duration is desired. Dependant upon the actual bleed rate of the hydraulic lifters, the valve may not open to its full advertised lift and duration. If the lifter preload is adjusted tight (close to bottoming) any loss in lift and duration can be minimized. This type of adjustment comes with the risks noted above and I doubt that I’d ever use it.

As far as lifter noise is concerned, my opinion is that the noise is much more dependant on the lifter design and manufacturing tolerances, primarily the bleed rate, than it is dependant on preload adjustment assuming that the plunger preload is set somewhere within its range of travel. If your lifters are making noise at 2 ˝ turns, tightening them another turn is most likely not going to make any difference.

I don’t consider myself an expert in this topic although I think I have a pretty basic knowledge about it, and enjoy thinking about and analyzing stuff like this. If I’ve made any glaring errors or you have differing opinions, feel free to fire back. And hopefully this helps some of you while not confusing the **** out of this topic even more.

 

These aluminum engines grow at full operating temps, while the chrome-moly(most) have a different growth rate.
Combine that with higher spring pressures on performanced-based engines, as well as higher cam lifts, and quicker cam ramp rates, and then toss in an oil that is very thin, at operating temp, and now the lifter is rapidly loosing it's ability to maintain pump-up. Fancy word for that is "hydrology".
We've chased this for years, and that is why we suggest the .140-150" load, as that is what we have found that works well.
Scott

 

No disagreement on anything in your post and I totally agree with the above statement. However, I believe you have over simplified the relationship between valve train noise and lifter design. As Scott points out, the variance in growth rate between various parts that affect valve train geometry cannot be over looked. As you have pointed out, "Primarily the bleed rate" is the heart of the matter with H-D OEM lifters. Believe me, valve train noise can be tempered by lifter preload or lack thereof as well as the viscosity of the oil being used or some combination of the two. Hence the popularity of HQ Black Ops lifter, S&S travel limiters; the new Woods lifter; Johnson HyLift; SBC lifters used in Harleys and the list of alternatives to H-D OEM lifters goes on. Most are sought after to quiet the valve train on performance oriented motors.

 

And I also mostly agree with you and Scott. Believe me, I understand there are many factors that can contribute to valve train noise although my post was primarily addressing the lifters, and even more specifically the lifters adjustment, contribution to noise.

From a theoretical perspective I just don't believe adjustment is that ctitical provided the lifter is adjusted "somewhere" within its range of travel and remains there throughout the engine's operation. Obviously if the preload was adjusted very close to the limit it may fall outside of an acceptable range as the engine temperatures change. That's not what I'm talking about.

I couldn't buy into some of the responses to my original post that in my opinion it would be better to err a little on the loose side as opposed to too tight if there was any question at all.

One of the responses even suggested that "loose" lifter adjustment could cause valve float. I simply don't see how that could be possible and belive misleading information such as that should be challenged, and corrected when warranted.

As far as noise goes from a "loose" adjustment - theoretically it shouldn't matter provided the adjustment isn't so loose that the lifter can't take up the lash in the valve train. Obviously, loose to the point of no preload is going to make quite a racket, but as long as there is some preload, any noise should not be attributed to lifter adjustment.

Again, my opinions here are theoretical in nature and do not come from actual Harley experience, but are formulated from many years of "general" mechanical and engineering experiences.

Thanks for your input.