What is the pressure on the lifter face?
Thanks for the detailed breakdown. Have you researched the design and tech behind medium and heavy duty diesels' lifters? They have been solid rollers for several decades. I have not looked into them in particular (just ran them for 28 years), but would suspect the reason for their million-mile longevity is 1) size. Every part in these engines is large, "overbuilt" relative to gas engines. 2) mild cam slopes. 3) low RPM operation. 4) Relative to size diesel-to-gas, the spring pressure is proportionally less. However what is NOT less is the injector cam lobe pressure, on the engines which use the camshaft to drive the injector. (Detroit Diesel). Particularly the electronic generation beginning in '89, where injection pressures were significantly increased for efficiency and emissions. The switch to overhead cam coincided with the increased injection pressures, probably by necessity. Can't remember the stat on the injector lobe roller-solid lifter and roller-rocker pressure, but it's in the several thousands of PSI. And the ramp (opening rate) is shorter but steeper than a valve lobe. The cam lobe and lifter roller tip which drives the injector is over an inch wide on the DD 60 series engines, and the roller is made of ceramic.Failure Data from a Bushing type Solid Roller Lifter
Let me say right up front, that this write-up is in no way slamming ISKY’ EZ Roll bushing type solid roller lifters. On the contrary, this info will show how well they hold up, considering that ANY solid roller lifter is a maintenance item that will need to be replaced regularly.
Here’s a little background info on solid roller lifters in general. Keeping an eye out for any lash changes, as well as regular removal and inspection is basically the standard recommendation for running solid roller lifters. But, the problem is, that ultimately may not save your engine. Here’s why, the root cause of their failure is metal surface fatigue failure from all the jackhammer pounding they take from not following the carefully designed cam lobe ramps, when they bounce around within the lash slop. They are not forced to ride nicely on the lobes like hydraulic lifters are. And since solid roller lifters don’t always directly ride on a lobe, the opening/closing lobe ramp design goes right out the window, and the roller gets smacked by the lobe, or smacks down on the lobe, depending on if it is rising of falling. The larger the lash, the worse this is. Eventually, this repeated over and over jackhammer pounding takes it toll, and metal surface fatigue failure bites you. You can’t predict it, you can only see it once it begins. And to add insult to injury, you could inspect your lifters one day when they look and feel just fine, and the next day they can suffer metal fatigue failure and things go south.
Bushing type solid roller lifters are way more durable than the needle type, because the needles only make a very tiny line contact (thus extremely high psi loading values are seen), so they are severely overloaded in this application. Plus, in .842 lifters, only the bottom 3 needles take all the load. They are just a failure waiting to happen.
But, the bushing type lifters provide a far larger surface contact (thus they see far lower psi loading values). ISKY says their EZ Roll bushing type solid roller lifters provide a 350% higher load rating than comparable needle type solid roller lifters. However, even the bushing lifters are not immune to failure. The bushing type lifters are subject to roller OD metal fatigue failure, but the needle lifters are subject to “BOTH” needle and roller OD metal fatigue failure.
And this brings us to the subject of this write-up. A car Forum member contacted me about a solid roller lifter that had failed in his engine. He knew I had performed root cause failure analysis on a few sets of failed needle type solid roller lifters, a few years back. So, he sent me his bad bushing type solid roller lifter for failure analysis.
He runs a 467ci Mark IV BBC in his street Hotrod, that see’s a lot of “spirited driving”. The rev limiter is set to 6800 rpm, though the most common normal rpm seen is in the 3000 to 3500 range. his cam specs are 243*/249* duration at .050 tappet lift, 112 LSA, and .668 lift. Lash is .008 cold, .014 hot with aluminum heads. Spring pressures are 210 lbs on the seat, and 525 lbs open. His solid roller lifters are .842 diameter ISKY EZ Roll bushing type.
He doesn’t let it idle. As soon as it fires, he starts driving although not too heavy on the gas until it warms up. He also pre-heats it on chilly mornings with an oil pan heater and a block heater. He also uses an Amsoil pre-luber. And he has been using Valvoline 10W-30 with a can of Moly Slip E added with each oil change, at approximately 1500-2000 miles. Valve lash gets checked a couple of times a summer, as does spring pressure. He put 25,000 miles on these lifters when he had this lifter failure that took out the associated lobe, and the debris from all that also opened up the lifter bore. The whole thing required an engine rebuild. Not fun, to say the least.
Here are the results of my analysis:
The remaining good lifter of the pair, for comparison:
Roller OD looked fine, and OD = .7500
Bushing ID looked fine, and ID = .3200
Axle looked fine, and OD = .3176 to .3179, with average = .31775
Bushing/axle clearance = .0021 to .0024, with average = .00225
***
Failed lifter:
Roller OD was completely destroyed from a text book case of metal surface fatigue failure, which is exhibited by flaking and pitting called spalling. The OD = .5870 to .6178, with average = .6024, so about .150 worth of diameter had flaked and crumbled off, thus destroying the associated lobe in the process.
Bushing ID generally looked alright, but there were signs of debris having worked through the clearance, causing wear and some scratches. The ID = .3223 to .3230, with average = .32265.
Axle looked fine, and OD = .3173 to .3182, with average = .31775
Bushing/axle clearance = .0041 to .0057, with average = .0049
BOTTOM LINE:
He did quite well with these ISKY EZ Roll lifters in terms of how many miles they lasted, even though it ended up causing a rebuild. Solid roller lifters in general, are a fairly poor design, because, as mentioned above, they are subject to the non-stop jackhammer pounding as the lifters bounce around within their lash slop. They get pounded because they cannot faithfully follow the lobe’s opening and closing ramps. Eventually, the pounding takes its toll, and the unavoidable metal surface fatigue failure results.
And for the record, NOTHING you do with oil or oil additives will make any difference here, because oil has absolutely nothing to do with this type of failure. Idling also has NO affect on this failure either. Idling generates the lowest loading and pounding these lifters will ever see, because the valve train acceleration is at its lowest value during idling.
This problem is simply a fact of the Physics involved, and cannot be avoided with this design. So, there is no absolutely safe plan when it comes to running solid roller lifters. They can fail at seemingly any amount of time or mileage. All you can do is replace solid roller lifters with fresh ones at an interval before metal surface fatigue failure results, which may take out your engine as well. What that interval is, is the million dollar question, for which there is no clear absolute answer. Everyone has to make their own judgment call on that. Words to live by – you can never replace solid roller lifters too often…
Correct. In the later part of my trucking days when the Quik-Change oil shops came on the scene, began paying the extra few bucks for oil analysis. Long-and-short of it, changed filters every 10,000 miles (about 220 hours) and Rotella conventional oil was still at 30% necessary detergents at 60,000 miles. Went from "by the book" 10,000 mile oil change interval to 60,000- 75,000 miles. Granted this was on a clean-burning Detroit 60 Series Electronic Control engine. Greyhound has had a 100,000 mile oil change schedule forever, as well as some of the large trucking companies.I have an issue with the statement, "No motor oil can ever go 20,000 miles". (I know I cut off the important part), I drove a company truck that we never changed the oil. Only added to when needed, if we ever checked it all. Just add a lil gear oil so it stunk real bad when full, when you didn't smell it anymore, add a quart or two.