The engine you spent a month carefully assembling has just fired and is running great while you carefully monitor oil pressure and break in the flat-tappet camshaft. The feeling of euphoria that washed over you when the engine lit for the first time is soon followed by a crushing low. You followed all the proper procedures for breaking in that cam, but something’s not right. The engine runs sluggishly and a testdrive reveals a disturbing lack of power. A quick investigation reveals that the cam is dead—suffering from round lobe syndrome. That’s about the same time your friends all found someplace else to go, your wife or girlfriend hightailed it to her mother’s, and even your dog has suddenly disappeared. You are alone with your dead cam and looking for somebody to blame.
If it’s any consolation, we’ve been there, too. The 400 small-block Chevy budget engine that slouched its way through the May issue (“How To Build a 400ci SBC Torque Monster for $2,500!”) lathed 14 of its 16 lobes within minutes of fire-up and left us with a lump of iron that had to be rebuilt a second time with all-new bearings. This led us to pay more attention to the details required to make a flat-tappet camshaft engine live these days, because lubricants are changing faster than Charlie Sheen rants on TMZ. This story is as much about lubricants and what works and what doesn’t as it is about camshafts and lifters.
First, we’ll go through the basic procedure for how to ensure a flat-tappet camshaft will survive its first 20 minutes of life, since that’s when these new parts are most vulnerable. Then we’ll get into evaluating a whole new world of lubricants and how it’s probably a mistake to buy mom-and-pop oil for your old-school flat-tappet engine in this brave new roller cam world. We’ll even break down the latest changes in oil and how those numbers are scarier than getting a registered letter from the IRS.
Cam Break-In Basics
In terms of cam break-in we’ve learned some twists on an old story. In the old days, the drill began with coating the camshaft with that black moly grease. Today you’ll notice that most camshaft manufacturers are using a more viscous liquid. The new liquid performs the same job with fewer negative qualities. The next step in the break-in procedure was to preconfigure the engine with proper static timing and fuel in the carburetor, pressure-lube the engine within a couple of hours of startup for best lubrication, and ensure the engine started immediately upon cranking. This is critical because excessive engine cranking wipes the lube off the lobes before the engine starts. Perhaps the most important step in the break-in process is to bring the engine immediately up to a minimum of 2,500 rpm or more. This is vital because most V8 pushrod engine camshafts are not pressure-lubed. Instead, the cam relies on splash oiling brought up from crankshaft movement. A higher engine speed for the first 20 minutes ensures plenty of oil reaches the camshaft. Another tip is to vary the engine speed throughout the initial 20-minute session to ensure that random splash oiling reaches all 16 cam lobes. Of course, it almost goes without saying that the engine temperature and oil pressure are within specs during this crucial break-in time.
All of the above has been covered in detail in stories that date back over three decades and has probably achieved near rite-of-passage status among car crafters. While most enthusiasts are aware of the significant changes in oil, what has received much less attention is the importance of using moderate spring pressures to ensure proper life span. For example, we used a set of typical Z28-style valvesprings in our most recent small-block. They measured 130 pounds on the seat, and that may have contributed to killing the camshaft. During our postmortem investigation, many engine builders said this seat pressure, combined with the open pressures of around 350 pounds, might have been borderline excessive for break-in. These same engine builders now avoid seat pressures above 100 pounds and prefer springs of around 80 pounds on the seat. This reduces the load on the lifter and enhances the potential that the cam will survive. Another engine builder suggested that if the flat-tappet lobes are centered in the lifter bores it can contribute to reducing lifter spin, which will also kill lifters.
It’s All About Oil
While flat-tappet cams and materials haven’t changed much in the last 10 years, engine oil and other lubricants have mutated rapidly as the demands for improved power, emissions, fuel economy, and extended drain intervals have continued to escalate. Most car crafters are aware that OE demands for a reduction of zinc and phosphorous additives (commonly referred to as ZDDP, which is the abbreviation for zinc dialkyldithiophosphates*). Zinc and phosphorous are used as antiwear additives with calcium, sodium, and magnesium considered detergents, while molybdenum and boron are friction modifiers. The demands for lower concentrations of ZDDP occurred because it is inevitable that portions of oil vapor (including ZDDP) will easily enter the inlet system via the PCV system. Once combusted, the ZDDP eventually coats the precious metals in the catalytic converter, reducing its efficiency. The OEs requested a reduction in pre-1993 levels of 1,200 parts per million (ppm) of zinc and phosphorous to 800 ppm. The American Petroleum Institute (API) responded with the SM category that has recently evolved into the SN standard oil for new cars. The API SM standard almost immediately began causing cam lobe failures in engines running aggressive flat-tappet hydraulic camshafts, and it has become clear that this oil should not be used without some kind of additive during the critical break-in period. But even if a new camshaft survives initial break-in through the use of higher ZDDP content additives like GM’s Engine Oil Supplement (EOS) or Red Line’s Oil Additive, there are still long-term durability questions if the engine was treated to typical off-the-shelf API SM oil.
As a hedge against problems, many enthusiasts began using diesel oil with higher ZDDP levels. This is a solution, especially if you don’t have access to specialty or specific break-in oil. Shell (and others) offers 10W-30 Rotella T diesel oil as opposed to the more traditional thick diesel engine oils. The best solution for breaking in a new flat- tappet camshaft that involves the least risk is to use the specifically blended break-in oils from companies such as Brad Penn, Comp Cams, Edelbrock, Joe Gibbs, Lucas, and Royal Purple. Break-in oils are blended with higher concentrations of ZDDP to accommodate the severe sliding friction present with a new cam and lifters. Since high detergent levels tend to clean the zinc and phosphorous from high-wear surfaces, evidence suggests the ideal blend for a break-in oil is sufficient levels of ZDDP combined with a lower detergent concentration. This allows the zinc and phosphorous to do their job.
Once the camshaft is fully broken in, the engine still needs sufficient antiwear protection beyond what API SM and SN oils can provide. Specialty oil from Comp Cams, Edelbrock, and Joe Gibbs or race oils from Amsoil, Red Line, and Quaker State offer critical antiwear advantages over API SM or SN oils, providing additional antiwear protection for flat-tappet cams and lifters. While these boutique blended oils cost more, they also offer an important level of insurance against losing a cam. Like those old commercials used to say: “All motor oils are not alike.” Today, that statement has never been more accurate.
Oil Test Results
The following chart contains results from 10 different oil samples sent to Polaris Laboratories for additive testing. Polaris Labs offers a very affordable single sample test for $22 that will deliver not only the metals listed in the chart below but also contaminant and wear metal results that will quickly present an accurate picture of contaminant issues inside your engine. This is also a great test before buying a used engine or car. It took less than a week to obtain results.
Current API SM and SN oil limit ZDDP (zinc and phosphorous) levels to 800 ppm. While ZDDP break-in level recommendations for flat-tappet camshafts vary widely, it appears that concentrations of around 1,500 ppm or above are appropriate, and as you can see from our testing, most of the break-in oils achieve that level. Substantially higher levels of antiwear agents do not necessarily guarantee reduced wear. Once the engine is sufficiently broken in, specialty oils for flat-tappet camshafts with ZDDP levels of roughly 1,200 ppm or higher are acceptable. Note that we also tested an older Mobil 1 API SJ oil, and the zinc and phosphorous were right around 1,300 ppm. We did not include all the results that Polaris delivered, but we did list calcium, which is a detergent additive. According to Lake Speed Jr. from Joe Gibbs Racing, reducing detergent levels for break-in oil allows the zinc and phosphorous to remain in place in high-friction applications such as the interface between the camshaft and the lifter. Normal high detergent concentrations do a great job of cleaning, which unfortunately also removes portions of the protective ZDDP layer. This is why Joe Gibbs reduces the percentage of detergents in its break-in oil.
Also note that we tested both new Royal Purple break-in oil and the oil we drained from our small-block with the failed camshaft. The zinc and phosphorous levels were slightly lower than we expected, as were the levels in Brad Penn, especially when combined with higher levels of detergent. In the Royal Purple used oil sample, the phosphorous level was 920 ppm, which is only about 15 percent above SM 800 ppm standard. Conversely, the Lucas Break-In SAE 30 pegged the zinc-o-meter with a 6,400-ppm count.