It is always nice to have a look at the failed components prior to taking a stand on the possible root cause of a failure. As long as I don’t have any skin in outcome, I’m comfortable going out on a limb with this one.
The short answer is that IMHO, the camshaft and tappet failure began with a failure of the bearing in the tappet roller. There is an outside chance that a foreign object somehow became lodged, seizing the roller, but that is a stretch. It is my sense that the tappet roller from your machine isn’t squared off like one pictured because the square roller was run longer in a failed state. I recommend that you take into consideration that both Harley-Davidson and Jim’s Machining have changed the material (H-D) and construction (Jim’s) of the lifter in order to resolve issues with failed rollers in high performance Twin Cam applications. If you still have your lifters, it is a simple matter to drill off the end of the axle pins to remove them and visually inspect the bearings, rollers and races.
The long answer is that prior to the mid 1980’s it was not at all uncommon for a tappet roller bearing to fail, sometimes resulting in a squared off roller. This failure always destroyed the camshaft, sending pieces of motor mulch to the bottom of the gearcase. IMHO the tappet roller was easily the weakest link in the late Shovels and early EVO’s. Machines built prior to ’73 had other components competing for the title of “Weakest Link”.
Reliability issues with the early tappets resulted from a tolerance stack-up in the tappet body and the roller’s inner bearing race. It appears that manufacturing the inner bearing race with an axle pin parallel to the bearing surface was a significant challenge. The separate inner bearing race was eliminated in the later EVO lifter, and the axle pin was utilized for the inner race. The result of eliminating the separate inner race was dramatic, and now this failure is practically unheard of in stock and mild performance applications. This is remarkable when you consider the number of machines in service during that period relative to today. I bring this history up to point out that there was a time when the failure that you experienced was commonplace, and that the issue was resolved with a redesign of the tappet roller.
Today the issue with the Twin Cam tappet rollers in modified machinery is the result of increased load. The load is generated from the big valve springs, aggressive cam profiles and high engine speeds. Once again the focus at H-D and Jim’s is on the tappet roller. H-D no longer sources their Screamin’ Eagle lifters from Jim’s and Jim’s modified their lifters to include pressurized lubrication of the tappet roller bearing.
After the meltdown in the camchest of my ’02 gear driven 113” Twin Cam, I discarded my Screamin’ Eagle/Jim’s lifters and installed a set of Feuling lifters which I ran for a couple of hundred miles. After depositing the Feuling’s in the landfill, I dropped in a set of OEM lifters and haven’t looked back.
My recommendation, Hoist is to put the machine back together with your existing crankcase, either the stock OEM lifter, H-D Screamin’ Eagle lifter or the Jim’s lifter with pressure fed tappet roller lubrication. I urge you to run removable pushrods and remove and perform an external inspection of the lifters at 5,000 miles. At no more than 10,000 miles I recommend removing the lifters and disassembling the rollers to perform a visual inspection of the needle bearings and races. If the rollers pass the visual inspection I would buy another set of the same lifter, install them and relax a little.
As I mentioned earlier, I am running OEM lifters in my 113, and I have another big engine that will run the Jim’s Power Glide 2’s; at least until I see a reason to change them. I will go through the same inspection ritual on my personal machinery that I recommended for you.
Regarding Alan from Fueling explaining that the camshaft centers of their camplate do not line up with the centers in the H-D crankcase. That seems to me a little like saying “the sky is occasionally blue”; of course they don’t line up. It is unlikely that Fueling uses the same technical plan or Blueprint that Harley-Davidson uses. Does H-D share their technical drawings/Blueprints with Feuling? Maybe Feuling based their Prints on a Twin Cam engine that they acquired; if so, was that engine manufactured somewhere close to H-D’s Print specification, or near and possibly beyond the tolerance limit(s)? The issue is aftermarket fitment 101 and whether H-D shares intellectual property with Fueling. My sense is that H-D does not, and if that is true then it is unlikely that there is a high degree of relative precision when comparing the various center points on Feuling’s camplate with the same points on H-D’s crankcases.
Consider the complexity of the manufacturing process with EVO’s and earlier machines with removable tappet blocks. Also consider the high number of variables that must be controlled during the manufacturing process in order to produce consistent, precision alignment of the gearcase components in these early machines. It is my sense that relative to the EVO, precision alignment in the Twin Cam’s camchest is a non issue.
The attachment’s four images are:
Top Left - separate inner bearing race used on the early EVO tappet rollers. Shovelhead and earlier are the same except smaller roller OD.
Bottom Left – late style EVO without separate inner race.
Center - early EVO lifter with inner race in full fail mode.
Right – just for grins, a tappet roller from an early Knuckle which didn’t use needle bearings.
As always this is just my humble opinion.
djkak
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