540 RAT

In order to explain everything involved with this complex issue, the write-up is extremely long. However, those keenly interested in this problem, may want to take a look anyway. Perhaps printing it out, then reading parts of it as you get a chance, might be the way to go.

I believe I have found the root cause for solid roller lifters failing prematurely in street motors. Hopefully others can benefit from this information as well, so I wanted to share my findings with like minded professionals and enthusiasts. To do that, I've sent this out to various Hotrod type magzines and web Forums. This is what I found with my particular combo, but of course your results may vary. Though I have to expect that this is likely a common issue among all engines with the same type of lifter oiling design.

I'm in the process of personally building an all aftermarket 540ci BBC. I'm using a Dart Big M std deck block, along with a Comp Cams billet solid roller cam, Crower Severe Duty solid roller lifters (using 17 needles, each with .071 diameter) with HIPPO, and Crower stainless full roller rockerarms. The cam is 266*/272* @.050, with .700" actual measured valve lift with .016 lash. Valve spring pressure is 280 lbs on the seat, and 700 lbs on the nose. I'm going through the entire engine very carefully and blueprinting everything. In the process, I made a startling discovery, which could be easy to miss. I found it when I looked through the oil passage at the front of the block, with all the pipe plugs out. The Dart block oils the lifters from the front of the block. At max lift, the 7/16 or .4375 diameter oil passage that runs through the entire lifter bank, is within .080" of being entirely shut off by the lower edge of the lifter oil band, nearly stopping the oil flow through and to the lifters down the line. In addition to mechanically blocking oil flow, you have the flowing oil dynamic issue, of the likelyhood of reverse pressure spikes as the oil passage is effectively slammed shut. This is similar to a large ocean wave slamming into a concrete sea wall, and spashing back the other way. The size of the block passage itself isn't all that important as long as it's big enough. What is important is the amount of opening that remains during the up and down motion of the oil band on the lifter. More on that below.

When I talk about lifter oil flow, I'm talking about having at least enough flow IN, to keep up with the bleedoff flowing OUT. That is the minimum flow required to maintain oil pressure. Any less flow IN, than that minimum, results in a loss of oil pressure. With insufficient flow/pressure, roller lifters have to get by with only bottom end oil splash, residual oil present and any spurting, sputtering or gurgling oil that does make it in through the passage. Roller lifters don't have the benefit of any oil wedge action holding needles and rollers apart, like bottom ends have with their concentric design and uniform clearance. So the only thing between premature lifter wear/failure, or lasting as long as we'd like, is a steady flow of pressurized oil to both lubricate and cool. We've seen noticeable improvement with pressure fed needles over the earlier type that didn't have that. This supports just how important enough oil is, though even the pressure fed needle type still don't last as long as we'd like. The load on the needles is high as lifter upward acceleration begins, and at max lift, that 700 lbs "on the nose" spring set, will put about 1200 lbs on the lifter needles, due to the rockerarm ratio involved. With my particular lifters, only 3 of those little needles are carrying that 1200 lb load at the point of contact. The lifter needles all spin the same direction of course, but since they are not caged like a wheel bearing, their side surfaces not only press against each other, but as one surface is going up, the other is going down. Without enough oil, it's easy to see how wear and/or outright galling can occur, which spells the beginning of the end of the lifter.

Some Pontiac and Chevy LS engines feed the lifters individually from the side of the lifter bores rather than in-line through all the bores in a bank. With the "individually from the side" oiling design, individual lifter position doesn't affect oil flow to the others, so there is no issue with those engines. Dart stayed with the old BBC stock "in-line through all lifters" oiling design. This old "in-line oiling" design means that the oil flow to a particular lifter in that bank, is affected by the lifters in front of it……..not good!! If you wonder why Chevy would design something that bad, the answer is, for their needs, they didn't. If I had only around .550" valve lift or less, I would have NO OIL RESTRICTION AT ALL, NONE!! So, for stock or mildly modified engines, there is no oiling problem with the in-line lifter oiling, they won't see our lifter failure issue. Only big lift, street engines have the oiling issue. Race motors are typically watched much closer, and any issues with lifters will usually be caught before anything is damaged beyond the lifter itself.

When I first came across this "blocking the oil flow" issue during my build, I thought, how could this be, wouldn't all this be figured out by now? But then, almost shutting off oil flow at max lift is just a momentary thing, right? So maybe it's not that big a deal……or is it? Not being one to just assume things are OK, I decided to look into it further in order to really know for sure. This whole pursuit became very involved and tedious, was extremely time consuming and the measurements were somewhat difficult to do with an acceptable degree of accuracy. On top of that, due to the nature of the oil passage/lifter interface being curve on curve, the math was difficult enough that hand calculations were out, so I modeled the interfaces on the computer, and had it calculate the orifice areas at many different positions. The analysis ended up being so involved that it is likely beyond what the typical professional or enthusiast would care to pursue. More below on simpler suggestions.

I started out by considering the orifice area in square inches, that was needed at the front of a bank, to support the bleedoff of the 8 lifters behind it, vs what I actually had. Then the next lifter interface in, and the bleedoff of the 7 lifters behind it, etc, etc, until I had accounted for the whole lifter bank. I also accounted for the oil restricted zone overlaps due to firing order, so as to not add them in seperately, which would skew the results. The bleedoff I'm referring to, is of course from lifter to bore clearance, the needle bearing feed passage diameter, leakage at the end of the pushrod from lash, and the oil squirting out of the rocker arm up top. In my paticular case, the rocker arms are counterbored at the pushrod socket, so oil never stops flowing out of them, no matter what the angle is between the pushrod and rocker. Good for oiling valve springs and rockers, but not so good in terms of bleedoff. Then I determined how much the lifters would have to move down to enlarge the orifice area, in order to flow enough oil to support all the bleedoff, and the crank angle involved with that. My lifter to lifter bore clearance is .0015", more clearance would put you in worse shape due to even more bleedoff. I have one .024" needle feed hole in each lifter, more holes would put you in worse shape, again because of additional bleedoff. And I have .700" valve lift as mentioned above, more lift would put you in worse shape, because of closing off the passage even more of the time. Its all about the amount bleeding off vs the amount that can feed in. Ultimately I came up with individual crankshaft degree ranges where the oil flow restrictions could not support the bleedoff taking place. Then I added up all those seperate ranges for a total number of crankshaft degrees where I had the problem.

In the end, I found that I didn't have enough open oil passage to support all the lifters in the bank, about 360* out of 720* for a complete cycle. In other words, I had a serious oil flow restriction happening about a whopping 50% of the time. That result prompted me to double check all my analysis, to make sure that number was in fact correct, which took even more time. The results were correct, so things checked out to be far worse than what that first glance might have suggested. This situation does not meet any engineering requirement, not even stock, not by a long shot. You'd expect these lifters to fail, and be surprised if they didn't. It's not a matter of "will they fail", but rather a matter of "WHEN will they fail". We've wondered WHY these things don't last long enough, and that oil restriction is the answer, at least on my combo. And it's undoubtedly the answer on other combo's as well. The problem is so obvious with my engine, that it doesn't take an advanced degree in Mechanical Engineering to see it. Considering the adverse conditions these lifters operate in, it's amazing they last as long as they do. If they failed because of inferior material, we would expect failures to be more a specific manufacturer issue, and a more uniform failure across a whole engine, but we don't see that. In fact, we see failures from every brand of roller lifter out there, no matter who makes them or what they cost. In addition to that, restricted oil to the lifters means restricted oil up top. So, while this oil restriction problem is in the process of deteriorating the lifters, it's also reducing the life of the valve springs because of the reduced oil flow over them, which they depend on for cooling. So, it's a double whammy situation.

It's a situation of fix it now, or fix it later, but I WILL have to fix it. If I don't do anything to improve the problem, it is like playing Russian Roulette with my engine. The sensible thing is to fix it now, while I'm in the process of building the engine in the first place. So, with the block back from the machine shop, and already cleaned, the question is, what is the most workable way to proceed? The best way to fix the problem with the block I have, would be to do some plumbing in the lifter valley. Joining all the lifter bores together with a common oil pipe, would do the trick. But that brings with it, a certain amount of complexity, and potential for leakage and/or breakage while in use. Using a somewhat simpler method of plumbing, and simply tying both ends of lifter bank together would also do the job fairly well, but brings with it the same concerns. I prefer the KISS principle, so I decided to modify the oil band (the center area of the lifter that is smaller diameter) on the lifters themselves, which is much simpler.

To modify the lifter's oil bands, I ground a .100" chamfer on the lower edge, front AND back, at the interface of the lifter and oil passage. And also a .150" chamfer on the upper edge, front AND back, also at the interface of the lifter and oil passage. The lower chamfer still leaves about .200" overlap between the lifter body and block, at the lowest position of the lifter. This maintains lifter support in the bore as well as oil pressure. If the chamfer were too low, you'd be down below the edge of the lifter bore, and you'd not only lose lifter support in the bore, but you'd be blowing out oil and losing oil pressure, which would defeat what you are trying to do in the first place.

After the mods, I ran the complete analysis again to see how much I had been able to improve the oiling situation. The results now showed that my oil restriction occurs about 150* out of 720* for a complete cycle, or about 20% of the time. That was the best I could do with lifter mods alone. Still not ideal of course, but going from inadequate oiling 50% of the time, to only 20% of the time, is a HUGE improvement. In addition to that, the chamfers on the lifters smooth the oil flow into and out of the individual lifter bores, by tapering open and tapering closed. In so doing, they reduce the likelihood of those reverse pressure spikes mentioned above, which can occur when the original lifter oil band edges almost instantly slam off the oil flow. When you factor in that additional improvement, then the modification is likely even BETTER than what the 20% vs 50% might suggest.

So, I'm confident that with the big improvement the lifter modification made, when combined with two other aspects that I feel are critical, the lifters will finally have the reliability we've been looking for. I believe the two other critical aspects are:

1. ELIMINATION OF THE OIL FILTER BYPASS -
Because even minor damage to a roller needle can ultimately result in failure of the lifter, it is critical to prevent any debris, no matter how small, from ever getting to that needle area. In order to do that, you need to ensure that the oil filter is never allowed to bypass. Oil filter bypass valves, whether in the block or in the filter itself, are actually quite simple in concept. They open when there is typically around 9.5-10 (but that can vary, depending on the particular filter) psi delta across them. In other words, if a condition exists where temps, viscosity, oil flow from the pump, and oil filter restriction are combined such that the filter entry side see's, say for example 40 psi, but the filter exit side see's 30 psi or less, the valve opens and now you are pumping unfiltered oil. Any number of scenarios can bring that about. Of course the first thing that comes to mind is cold oil on start-up, but enough rpm (which increases the pressure against the filter, at least up to relief valve pressure) for the viscosity being used, combined with a restrictive enough filter (one of those fine 10-15 micron types for ex), and it's easy to see how you can bypass even at normal operating temperature. It's a scary thing, to think about how much bypassing is actually going on, because you can't see it on the oil pressure gauge.

To avoid all that, I'm using an oil filter bypass eliminator adapter, a Moroso 2qt high flow (moderate restriction) Racing oil filter which has no bypass in it (many oil filters do, even though they aren't advertised as having one, you have to carefully check to be sure), so as to avoid any significant pressue drop through the filter, and one or two Filtermags. This set-up will flow plenty of always filtered oil, while filtering out even the smallest particles.

2. USE A NON-CAVITATING OIL PUMP -
By design, conventional stock type spur gear oil pumps, will cavitate at certain rpms, whether stock or modified. At high rpm, the twelve individual spur gear teeth are simply opening and closing too quickly to completely fill the small segments between the teeth, creating gas bubbles that result in cavitation. Spur gear pumps have over seven times as many pumping pulses as a gerotor oil pump, at any given rpm. When a spur gear pump cavitates, the LIQUID oil being pumped can drop by as much as 70 or 80%, leaving it pumping mostly FOAMY oil, which is the last thing we need for our lifters that already have inadequate oiling. On top of that, shock waves from the cavitation, is what causes pickup tubes to break and housings to crack.

The solution here is to simply use a gerotor oil pump. By design, it's larger, slower, smoother "bites" of liquid prevent bubbles from forming, so it can never cavitate. This means the gerotor oil pump will pump liquid oil 100% of the time, and this all liquid flow will obviously benefit the rest of the engine as well. It's been my experience that gerotor pumps generate significantly more oil pressure at idle and at lower rpm than what spur gear pumps can muster, which is another big plus for our lifters. This is perhaps the final piece of the puzzle to increasing the life of our solid roller lifters. I'm using a Titan Sportsman gerotor oil pump, which is more expensive than a conventional pump, but I think it's cheap insurance for an expensive engine.

SIMPLE SUGGESTIONS FOR CHECKING YOUR OWN ENGINE:
Based on what I found with my engine, I can offer some simple suggestions for checking your own engine. This simplified method won't be as precise as doing the full exhaustive and time consuming analysis I went through, but it can get you close enough to decide if you should consider doing modifications. The single most important thing is to check how much lifter oil passage is still open at full lift. You'll of course need to have at least one lifter out of it's bore to do this. With a lifter out, roll the engine over until that lobe is at full lift in that bore. Now you want to measure the distance from the top of the lobe to the top of the block's oil passage that goes through the whole lifter bank. Using a scale and a flashlight will come to mind, but due to parallax error, you won't get accurate enough numbers to rely on. What works quite well, is to use a notepad's cardboard backing and cut out a simple measurement gauge with scissors, until it exactly touches the TOP of the oil passage while sitting on the nose of the cam. You may have to trim it a few times or even make a second one to get it right, but it isn't that difficult to do. Once done, simply measure it with a dial caliper and you have your distance. Then set your lifter on a flat surface and measure it from the bottom of the roller, up to the LOWER edge of the oil band on the lifter. If the lifter measurement is less than the lobe to passage top measurement, then you have some oil passage open at full lift. If you have bleedoff clearances fairly close to mine listed above, and if you have about .225" or more open at the top of the passage, then you should have no oil restriction and you're good to go as is. If you have less than that open at the top of the passage, if you have larger bleedoff clearances or more needle feed passages than I do, then you might want to consider making some modifications to improve oil flow in your own engine.

Hopefully this write-up has been helpful in giving others something to consider with their own builds. And maybe we can put solid roller lifter failures behind us once and for all.

540 RAT

Durango_Boy

Wow...great work.

Question: Does this problem occur in small block engines with after market roller lifters or is it more common with after market big blocks with after market lifters?

burners

Excellent work. You have obviously spent a huge amount of time working the problem. Have you talked to Dart? I would think they would be interested as well. They must not encounter similar failures on their Pro Stock engines due to the short duration of operation. I would still expect it to be an issue and they should be interested in such information.

Durango_Boy

Can you post some of the diagrams or images you created?

Ironcross

But solid roller camshafts are really for race applications. My experience is only in drag racing and based on only a 8000 RPM limit there are approximately 135 revolutions per second. Therefore those engines are only used for much less than a total of a thousand RPM`s in a full bore operation. Then torn down and inspected. Would you not think the extreme pressure of the valve springs continuous use to keep the lifter traveling over the cam profile correctly but used on a street or circuit application also contribuite to the failures and not merely oil problems?

norvalwilhelm

427hotrod/Jim warned me of this problem at the start of my 540 build up. I only have .630 lift and after looking into this I decided that I probably could get away with this restriction.
He suggested that I feed oil with a seperate oil line to the back of the block so oil is fed in both directions. I wish now that I wasn't so far along with the buildup when he suggested that.
I would go this route and redirect oil from right above the oil filter to the lifter passage in the back of the block. It would be a simple way to feed oil front and back.

turtlevette

How about going to dry sump?

Little Mouse

Seems like chrysler put a oil passage way along side all the lifters
and took oil off the center cam bearing to oil the shaft rockers.
they also did not use a gear oil pump on big blocks.

MotorHead

Mine live with no pressure fed oiling to the rollers at all, they don't have a hole or slot designed in. THey rely soley of the oil being flung around in bottom of the motor. Maybe this method of oiling the lifter/cam is underrated. I run oil restrictors in the galleys. I don't have a windage tray, I don't let the motor idle for more than 30 seconds. I have over 25,000 street driven miles on it now

Ironcross

If thats not a gear pump on my Chryslers what do you call it? Plus I use a dry sump and all that does is keep most of the oil out of the pan.

Durango_Boy

So if you're at a long light you slip it into 'N' and wind her up?

427Hotrod

Wow...Rick......great writeup!!

Since we've been chatting and e-mailing about this for the better part of a year now, I've seen the detailed analysis that you put into all of this. Trust me folks...he's done his homework!

While I had often thought about the restriction of the GM design (and most others), and considered various methods to improve it, I hadn't come close to looking at it to the detail Rick did. Once he got started he was like a man driven and he was able to quantify his thoughts with his math ability (he's an aerospace engineer) and analytical ability.

We may not have agreed on every point during all of this, but there is no doubt what you've outlined is definitely a solid foundation for a reliable oiling system...MUCH improved over what most of us are running around with for sure. I believe my ultimate deal will be to plumb the lines in the lifter valley next time mine is apart along with some trough to help hold oil. Hopefully all of this will keep these things alive a little longer. If not..flat tappets may be back in my future someday!

I haven't done any measuring on a small block to see what you end up with actually for *orifice* size when lifter is at max. Might be fun for someone to do and report back.

But I can guarantee you Motorhead that you are among the extremely fortunate to still have the same rollers in there after 25k miles. Good luck! That's a pretty healthy cam you have there too. I think G-kull had one last a pretty good while too. Maybe it's more prevalent on big blocks.

From looking at it all, it sure would have been nice if the Darts or Merlins would have just moved that lifter galley over to the side of the bores. Would have eliminated this as being a possible failure point.

Again, great work Rick and thanks for sharing it with all of us!!




JIM

MotorHead

Yes kinda funny because the guy in the Camry next to me thinks I want to race, but I gotta do it and do you think he knows the real reason I am revving the motor ?

427hotrod, I did have brinnelling on the roller of one lifter on the last inspection, so I replaced them all even though the other 15 were in pristine condition, it was a little over 25k miles

427Hotrod

I think you got your money's worth!!


JIM

calwldlife

I think I have seen oil systems that "pipe" between lifter sets.
You write up is logical, well expressed.

ZL1powr

Very nice piece of work. I am in the middle of building an aluminum 565 with a Brodix block. I assume the same issue exists with that block so this info is very timely.

jackson

That’s nice attention to detail & great work there sir.
IIRC, I addressed similar issue in a reply to a much earlier post … where I referenced lifter “waistband” and a lifter with a wasp-waisted band (kinda like an hourglass) made by Johnson for Joe Gibbs Racing (that's a flat lifter not roller).

Our circle track motors’ cams have a lift rule so we don’t have that alignment issue. However, I’m planning a motor for another app that may have band-to-galley alignment issue.

Here’s what I’m considering as a fix: With a die-grinder, lightly chamfer-radius the top & bottom of hole/lifter bore just as galley enters the lifter bore … in much the same way as crank journals' oil holes are chamfered. So ... the hole at side of lifter bore becomes oval and longer ... that's a total of 64 individual "cuts". What do you folks think of that approach???

632C2

Excellent write-up! Very informative and much appreciated by all of us.

Of course, now the hard part begins - real world testing. Please keep us posted as the miles pile up.

Steve

burners

Incidentally, who did you talk to in the Hot Rod magazine world? I can think of a few editors that would be very interested in this. I don't know if they would publish it but they would be interested.

ML67

Excellent write-up Rick. Well thought out and well written. Your side job as a technical writer is calling!

As we’ve discussed previously, I too have some reservations about this solving the roller lifter needle bearing issue. I would expect there to be some locality to the problem, ie cylinder nos. 1 & 2 lifters predominantly failing. From your analysis, there should be no (or significantly reduced) failures due to interrupted oil supply in LS, Pontiac and other engines using individual lifter oiling. I don’t believe this to be the case.

Second, I’ve always suspected the needle bearings have a finite life due to the extreme loading – even with “perfect” oiling.

Third, it is my understanding that oil filter bypass valves are used primarily to protect the filter media from pushing thru the center tube, and to a lesser extent protect the canister and seal from blowing out. While I agree unfiltered oil flowing at cold startup and other conditions through the bypass is undesirable; unfiltered oil flowing undetected 100% of the time through the filter due to media blow–through is worse IMO.

Fourth, you claim with lift under 0.550” you would have no lifter oil supply issues, this to me would suggest that hydraulic rollers with > 0.550” lift would be subject to the same oil supply interruption as their solid roller brethren. Even accounting for the reduced spring forces used in a hydraulic roller application, I’d expect to see *some* lifter failures if this were the case. I haven’t heard of any hydraulic roller lifter needle bearing failures. Looking at it another way I’d be curious how a solid roller lifter used with a cam < 0.550” lift, run with springs artificially adjusted to similar levels as for a .700” lift cam, would fare vs. a roller in a .700” lift application.

What do you think about the benefit of an oil accumulator to address startup – particularly for an intermittent use car? Would you expect lifters of otherwise identical design that have different width relief bands, to exhibit longer or shorter lifetime accordingly?

Again as we’ve discussed previously, don’t take my comments in the wrong light. Excellent write-up and well thought out. You have reduced the problem into manageable subsystems and used critical thinking and sound engineering principles to suggest logical solutions to each system. Thanks for posting. Now get that beast built and generate some real world data!