Ok ... here we go again. I know theres been a problem eating lifters/lobes on the flat tappet cams but these cars came that way and there are MANY of them out there that have 100k miles on them and are still going fine.
In your opinion is it the low zinc content in the oils or the quality of the aftermarket lifters?
If you bought the GM lifters/ delphi (manufacturer of GM's lifters) and use ZDDP or racing oils that have the high zinc levels do you think they would last on the street? Is it the oils or the lifters that are causing the failures??? just your OPINIONS... thanks ! Steve
Hi Steve,
This issue has been EXTREMELY well documented and quantified, especially in the case of Delphi/GM lifter wear.
Those who buy aftermarket lifters are on their own as far as quality and life expectancy goes. This is not to say that ALL aftermarket lifters are poor quality, but we have not seen a GM/Delphi lifter which showed signs of failure or wear due to material or manufacturing defects…yet.
Those building ultimate high-power engines are well served by installing a modern roller-follower cam design, but there are many reasons that stock type flat-lifter cams and followers are still installed during a rebuild. Certain classes of racing require stock cams and lifters, and those who are keeping their GNs or GNX’s in valuable collector condition will certainly not want to butcher the engines by changing to roller followers.
GM/Delphi lifters that have failed can be broken into two groups: lifters that fail soon after break-in and lifters that fail after many miles of satisfactory service.
The lifters that have failed soon after break-in are the victim of improper cam and lifter lubrication, poor cam surface treatment by the cam manufacturer, or an improper break-in procedure. By improper break-in procedure we are referring to breaking-in with ultra-high tension springs instead of low tension break-in springs, revving too high, or using a poorly performing break-in lubricant on the cam and lifters. If you are considering building an engine with flat-lifters, please pay special attention to the assembly/break-in lubricant you use. If it has not been specifically designed for flat-lifter assembly, we suggest that you use one that is. We also suggest that in the initial oil fill, you boost the oil’s ZDDP levels to a 2000ppm of phosphorus level or higher. This will give an extra margin of anti-scuffing protection to the freshly machined wear surfaces. An excellent primer on engine break-in can be found at:
http://www.zddplus.com/TechBrief12%20-%20ZDDP%20and%20Engine%20Break-in.pdf
(In the interest of full disclosure, we are introducing our new assembly lubricant called ZPaste next week. The reason we developed this break-in lube was precisely due to these kinds of failures!)
Failures with a cam and lifter after many miles of satisfactory service are certainly almost entirely due to insufficient anti-wear agents in the oil. As you point out, these engines can go hundreds of thousands of miles without any cam or lifter wear problems, if oils with sufficient ZDDP are used. When the engines were designed in 1986-1987, they were designed to use API SF oil, which contained ZDDP leves which result in 1200ppm to 1600ppm of phosphorus. Modern API SM oils do not have sufficient anti-wear characteristics to protect either these engines nor many other high-performance flat-tappet engine lifters from wear. This has been documented many times in the TR community alone. Once the cam and lifters show wear, the only solution is to replace them. Much more information on this topic can be found by reading the Tech Briefs at:
ZDDPlus™ - ZDDP Additive for Classic Cars - Agricultural Equipment & More
(Once again, in the interest of full disclosure, two years ago we developed ZDDPlus to address exactly this issue in order to protect our own TRs, and then began selling it in response to overwhelming demand)
If you have a TR engine that still has the stock GM/Delphi lifters and is not yet showing wear, we highly suggest that you maintain a ZDDP level resulting in 1400ppm to 1800ppm range of phosphorus. We have seen MANY TR engines which are currently showing little ongoing wear with stock cams and lifters at over 150,000 miles by keeping sufficient ZDDP levels. Our suggestion is that the most cost effective way to do this is to use high-quality SM oil and add one 4-ounce bottle of ZDDPlus. Ask around and I think you will see that this is not just an advertising statement, it has saved a lot of valuable iron AND money.
