BBC solid roller lifter failures - a root cause analysis
Like everyone else who is interested in BBC solid roller lifter failures, I wondered just what is really causing all these failures. Everyone talks about the problem, and some have ideas how we can make them live as long as possible. But at the end of the day, most all of them are going to fail, no matter what you do to try to help them, at a time/mileage that most of us consider premature. Yes, there are some reports of long lives, but that is mostly luck of the draw and not something that you can count on with any regularity.
As far as I know, no one has ever done an actual root cause failure analysis on these lifters to see what is really going on. So, in an effort to preserve my own nearly finished 540, I decided that if I wanted that info, I'd have to do it myself. So, I thought I'd post my findings for others who might be interested as well. I managed to get my hands on failed std diameter .842 solid roller lifters from 3 different BBC's. I would have liked a wider sampling, but these 3 motors spanned the spectrum from relatively mild to relatively wild. The specs are:
1. 408ci BBC, 243*/249* at .050, .663"/.655" lift, .018/.020 lash, 210/567 lbs spring pressure, Chevron Delo 15W40, Isky Redzone lifters failed at 3,000 nearly all street miles.
2. 540ci BBC, 266*/272* at .050, .678"/.688" lift, .016 lash, 260/650 lbs spring pressure, Redline 20W50, Crower HIPPO's failed at 5,000 nearly all street miles.
3. 632ci BBC, 277*/292* at .050, .848"/.824" lift, .026/.028 lash, 325/875 lbs spring pressure, Mobil 1, Redline, and Royal Purple Racing 20W50, Crower HIPPO's failed after 1 1/2 years. Mileage and driving style not documented.
So, I took them apart one at a time for careful analysis. I figured to get to the bottom of it all, if needed, I'd also Rockwell test the parts and send them to a metallurgy lab for detailed analysis. As it turns out, no matter what the cam, lash, springs, or oil used, they all suffered from the exact same mode of failure, in the form of extensive surface pitting on the axles and needles, which is also called spalling (no indication of an oiling problem such as galling was found at all). The axles were the worst in all cases, which make sense, since they are softer, which allows for the swaging at their ends which holds them in place. All this pitting is caused by metal surface fatigue failure. And this is brought on by the part being overloaded for its size, which sends the stresses of the metal so high, that its fatigue life is lowered to an unacceptable level. Since this failure was totally obvious, much like a bullet wound through the head, the cost and hassle of further analysis was not necessary. That being the case, there is essentially no defense against this fatigue failure with .842 lifters. They are just too small for the job we ask of them. If they are made bigger, and of course some are available a bit bigger (though they may not really be big enough for acceptable fatigue life), then the stresses can be lowered, thus increasing fatigue life. Using .842 lifters is just convenient for use in existing lifter bores, but this size is not what engineers would design from a clean sheet of paper, or a blank computer screen, for an application such as this. All most can do is closely monitor things to see when they start to go. And hope you can replace them before they take the engine with them. The other thing that was very bothersome about all 3 sets of failed lifters, is the fact that the roller OD's all showed the same fatigue failure pitting. Some had totally failed, and some were just beginning to fail. And with all different oils, cams and spring pressures being used, showing the same problem, there is really no defense against fatigue failure here either. This failure is actually worse than a needle/axle failure, because with close monitoring, you can usually catch the needle/axle failure before it takes anything else out. But with a roller OD failure, by the time you see it show up in terms of extra lash, it is almost guaranteed to have already taken the cam lobe with it, and perhaps even more. Not a very comforting thought.
Since I now see that the needle-type solid roller lifters for BBC's are basically hopeless, I pulled the new Crower HIPPO's out of my as yet un-fired brand new 540, and replaced them with newer Isky EZX bushing-type roller lifters, since they are more or less the only game in town for that type design. By all accounts that I've come across, these EZX's are much more durable than the needle-types, with respect to the needle/axle problem. So I'll give them a try, even though I really don't like some of their other design aspects. I suppose overall, they can't be any worse than the needle-types, and will hopefully be much better. But, unless those EZX's have better material being used for the rollers, than the basic Redzones, then they also can only last as long as the roller OD's, no matter how well the bushing/axles hold up.
For those who might be interested, here are some things I came across when installing those Isky EZX's in my Dart Big M block with its Comp Cams billet custom solid roller cam:
1. The diameter was larger than Isky told me they would be, thus reducing the lifter to bore clearance to less than I'd really like, but the motor was built already at this point, so honing the bores was not an option. It should be OK, but it is at the minimum, so it does concern me a bit.
2. The pushrod seats were about .040 higher than were the seats in my previous Crower HIPPO's, so I had to get another set of shorter pushrods to maintain the rocker geometry that I had ever so carefully setup with my AFR 335cc CNC heads. So, that cost me even more money, even though Isky told me there would be no change in that regard.
3. Isky's so-called high pressure bushing oiling holes are horizontal holes just above the axle, in the front to back direction, and do not get oil through a passage from the pressurized oil band up above like the Crowers and other lifters do. These Isky bushing/axle oiling holes hang below my lifter bores when on the base circle, where they get no oil at all half the time. Those oil holes will see some oil when they are up in the lifter bores, where there is some oil pressure, though restricted by the amount of lifter to bore clearance available. And they will also see a shot of actual pressurized oil during the relatively brief time (maybe 90* camshaft, give or take), when the holes reach the block's lifter oil galley at max lift. But the way the bushing/axle gets most of its oil, most of the time, is because there are oil holes above the roller, shooting oil onto the OD of the roller. The spinning rollers will throw the oil off and outward just like water off a spinning tire in the rain, but it hits the underside of the lifter body, and then comes back down the sides of the rollers onto the axle, where it can sort of work its way into the actual bushing/axle interface. Overall, I don't like this poor oiling design. Though it does apparently work well enough to get by. But, having the bushing/axle area get consistent fulltime oil directly from the oil band like other lifters do, would be far superior.
4. The lower thrust surface below the large oil band, is really way too short. It doesn't wrap somewhat around the roller like the Crower HIPPO's do, which is a much better design altogether. Some of the Isky's I took apart, showed excessive wear on that shorter thrust surface below that oil band. This is also an inferior design aspect that I don't like.
5. The precision outer diameter surfaces of the lifters were not machined high enough, which I didn't expect to have to look for originally, and so I had 3 lifters stick in their bores. All they had to do was machine about another .100 higher, and it would be no issue. My original Crowers were machined correctly, but the Isky's were not.
6. The one good thing I found with the EZX's is that the large pressurized oil band is lower than they were on my previous Crower HIPPO's, so they don't try to restrict oil flowing through the lifter oil galley like the Crowers would at max lift.
All in all, I was not very happy with my $1,000.00 Isky purchase. But considering the solid roller lifters available, they apparently are the lesser of evils. So, I'm crossing my fingers and hoping that they will hold up better than the rest. I guess guys like us who insist on running solid rollers on the street are a bit crazy………..