From 1995 to early 2012, I had a 406 SBC with a Lunati solid roller setup that ran flawlessly. The main bearings finally gave up so I built a 434. This engine used a Comp solid roller that ate the lifters twice. After a few disasters with this one and a failed block, I bought a new Dart block and went the 427 route.
I’ve always used Rotella 15w40 due to the higher zinc which I thought was better for cushioning bearing surfaces. Now with roughly 10,000 miles on the 427, this one has crapped a lifter. My question is are the lifters just not made with the quality of their predecessors? Valve lash was checked religiously. All the ones I’ve run were needle bearing style. Any advice would help helpful.
G.M.
It would be difficult for me to make any kind of an accurate evaluation of the problems you have been having except for one point that you made in your email. I do know that diesel engine oil is not a good high performance lubricant. While the oil does provide a level of ZDDP—later formulations of diesel engine oil such as CK-4 have removed much of what was a higher concentration of zinc and phosphorous. What’s worse is that diesel oil contains very high concentrations of detergents to clean soot from the engine. What most enthusiasts don’t know is that detergents actually strip away the ZDDP protective layer so you have a bad situation where the ZDDP level is significantly lower in modern diesel oil while the detergents are higher. This is not a good combination.
We looked up the Rotella 15w40 and found on the internet that the ZDDP levels are indeed higher than normal CK-4 diesel oil at 1,200 ppm. This is good, but the bad news is that the calcium levels come in around 2,300 ppm. These are very high levels that tend to counteract the ZDDP. The most recent information from our friend Lake Speed, Jr. is that balancing these ZDDP and calcium levels wll produce far superior results.
GM discovered that the culprit with much of its problems with low speed pre-ignition was high concentrations of calcium which is used as a detergent. New API engine oils now have drastically lowered or eliminated calcium as a detergent and combined with even 800 ppm levels of ZDDP offer improved wear protection because of this balance between lowering calcium levels and decent levels of ZDDP. So you should be able to see that using a diesel oil with high calcium levels is not helping with protecting the high load presented with a roller camshaft and roller lifter.
You would be much better off using dedicated race oil like Valvoline VR1, Lucas Hot Rod and Classic, Driven Racing Oil, or Summit Racing Performance Oil. These lubricants increase the ZDDP content while lowering the detergent levels. This will mean you will need to change the oil more often but it’s far better than replacing lifters. You might also look into lifter bore clearance as a factor although that’s probably not an issue with the Dart block but still worth investigating—if nothing else, it eliminates this as a variable.
When your lifter failed, did the needles escape or was there a different form of failure? If the problem is the interface between the lifter wheel and the cam itself – that sounds like a lubrication issue – rather than a materials failure. There’s a lot of talk on the internet about “Chinesium” in regard to poor metallurgy but no one has produced any real facts. My thinking is that these accusations could be engine builders deflecting blame. My opinion is that these failures have more to do with poor engine building techniques or poor choices in lubricants.
I’m not specifically saying this was your fault but rather that I see most failures with flat tappet and roller cams can be traced to a series of errors on the part of the engine builder or tuner. To this point, I would strongly suggest breaking in your next engine with dedicated break-in oil from a reputable company like from Driven Racing. A good break-in oil will offer just the right amount of ZDDP along with zero detergents. Too much zinc can actually cause harm by increasing the acidity level of the oil.
Another question would be what valve spring loads are you using? High spring loads combined with poor lubrication will also cause a failure that looks like poor metallurgy. Another abusive technique is allowing the engine to sit on the rev limiter on the starting line in drag racing. That popping sound from the exhaust means the lifters are bouncing on the lobe which will kill a set of lifter roller bearings in mere moments. Roller bearings are highly susceptible to impact loads that create a tiny flat spot on one needle bearing. This prevents the needle from turning—and failure is then imminent.
We’ve seen good engines kill roller lifters. This happened to a friend with a professionally-built small-block Chevy with quality roller lifters. The engine was equipped with high spring pressures and even with good oil, a mechanical roller lifter still failed. Usually you can catch the failure before it happens by checking lash. As you mentioned, you were watching the lash carefully. This tends to point to a quick failure which could be any number of things.
You might consider using a roller lifter equipped with bushings instead of roller bearings. These lifters are generally more expensive but one advantage is that if you experience some kind of failure, this won’t push those tiny roller bearings all through the engine. You’ve already experienced this so you know how much damage these little roller can cause. Most enthusiasts don’t realize that these tiny needle bearings can get caught in between the piston and the cylinder wall causing all kinds of nasty damage to the cylinder wall.
One item worth mentioning is that using a bushing style lifter requires much more diligence with changing oil more often as these bushing are very sensitive to fuel contamination or dirt in the oil. But they do work well and just might save your next engine.
Again, these answers are highly speculative but hopefully these may help. Used oil analysis is another tool you can use to help diagnose problems. SpeedDiagostix is a good company to work with. Lake Speed, Jr. owns and runs the company. He’s a wealth of information on lubrication.
“Another abusive technique is allowing the engine to sit on the rev limiter on the starting line in drag racing. That popping sound from the exhaust means the lifters are bouncing on the lobe which will kill a set of lifter roller bearings in mere moments.”
How does cutting spark to random cylinders or pulling ignition timing affect the springs or lifters?
Now, I *have* seen a valvespring-based rev limiter before (SBC, stock 100K-mile springs, Comp 280 Magnum). It would go to 5,500 and sound exactly like a 2-step. But that’s not the same thing.