Scared Flat Breaking in a Cam
Tom Keyes; Redding, CA: I am going to start my next project this summer: a ’32 DeSoto three-window coupe with a ’56 first-gen 354 Hemi, a four-speed trans, a Heidts IFS, and a Jag IRS. After reading your article on breaking in a flat-tappet cam (Aug. ’11), I have some questions. I’ve been in the hot rod hobby for more than 45 years and have never had a problem breaking in a cam before, so you scared me! My motor will have 10:1 forged pistons, mildly ported stock heads, a Hot Heads 2x4 tunnel-ram manifold, zoomie street headers with baffles, and a Hot Heads hydraulic flat-tappet cam rated at 0.485-inch lift and 280 degrees duration. Horsepower will be in the 350 to 400 range. Your article says there is a problem with today’s modern oils and “cam lobe failures in engines running aggressive flat-tappet hydraulic camshafts.” Just what is considered an “aggressive” hydraulic camshaft? The way I read the article, I assume only hydraulic cams have this problem, as you refer to hydraulic cams, not solid lifter cams. Is this the case, and if so, why? And about additives, do I just add a can or bottle to SM- or SN-rated oils with each oil change after the first 100 miles on the break-in oil? Thanks for your advice.
While in Santa Barbara shooting pictures of Christian France’s Coyote Fox, Staffer John McGann stopped by the Santa Barbara County Sheriffs’ Department headquarters for this photo op. The mechanics in the county garage were interested in the car’s transformation in the years since it left their care. A couple of the deputies asked if John could do the same to their cars, too.
Breaking in a cam
When I first read your letter, Tom, I thought, Wow, I didn’t mean to scare anybody.
But then it occurred to me that perhaps a little fear is a good thing, because it increases awareness of a potential problem. You bring up some excellent points that were not included in the story. Most important, the lubrication issue both from breaking in a cam and continuous-use standpoint is applicable to any flat- tappet camshaft/lifter system. What we’re talking about is what engineers call a sliding follower, as opposed to a roller follower like a roller lifter. It makes sense that sliding followers or flat-tappet cams create significantly greater sheer and heat, especially when additional load is created. This additional load comes from higher valvespring pressures used in a performance engine. Before 1993, the levels of phosphorous and zinc (commonly referred to as ZDDP) were unregulated and were in the range of 1,800 parts per million (ppm). With the American Petroleum Institute (API) SM in 2006 and the current SN standard, the maximum phosphorous was reduced first to 850 ppm and now to 800 ppm. API testing of stock, production, flat-tappet engines saw no significant wear problems, but these test engines used both very mild cam lobe profiles and (more important) very conservative (weak) valvespring pressures.
The problem with the API SM oil is that it clearly won’t stand up to an “aggressive” cam design and requires higher spring pressures. I used this term only because it is a difficult area to define. But let’s just say if you are using even a mild street cam with only 10 or 20 percent higher-than-stock spring pressures, the engine is entering a potential problem area–even after a successful break-in procedure. Let’s use some basic numbers. A stock small-block Chevy flat-tappet cam uses seat (valve closed) spring pressures of between 80 and 90 pounds with open pressure of roughly 250 pounds. At these loads, current API SN engine oil has sufficient ZDDP levels to prevent excessive wear. I’ve been using SM oil in my flat-tappet camshaft ’93 350ci GMC pickup for the last five years without a problem. The engine now has more than 120,000 miles and runs as well as it did when I first purchased it, but if I were to measure the valvespring load on the seat (valve closed), I doubt there would be more than 75 pounds of load. A strong performance cam can see an increase in seat pressure to 110 pounds and open pressure of maybe 300 pounds. Plus, a performance cam lobe is designed to quickly accelerate the lifter and generate more lift. This reduces the total contact area between the lobe and the lifter. This reduction in the contact area means the load increases dramatically. Phosphorous and zinc are high-pressure, antiwear lubricants. These additives are self- sacrificing, which means over time the additives are depleted. One reason oil needs to be changed is so these additives can be replaced. During our research, we found an additive product called ZDDPlus (ZDDPlus.com). The ZDDPlus product is a small, 4-ounce bottle of concentrated zinc and phosphorous designed to be used with between 4 and 6 quarts of off-the-shelf SM or SN engine oil that will raise the phosphorous level of the engine oil to pre-2004 levels. On the company’s website, we found several technical papers, one of which showed the results of an independent test with an engine that began with a phosphorous level of 1,800 ppm. After the equivalent of 2,000 miles of street driving, the phosphorous level dropped to roughly 600 ppm. While the results could be different for other engines, it’s clear the trend is that even after just 1,000 miles of driving, the levels had dropped by more than 50 percent. This information was found in ZDDPlus’ Tech Brief Number 8 on page 3.
One area I didn’t get into with the story (because it was becoming too long!) was oil additives. The oil companies tell you that you should not add anything to their oil because of possible “additive clash” issues. However, in the case of the ZDD additive, it appears you are merely doing what the oil companies used to do before the change to the API SM standard. This will probably draw criticism from oil chemists, but I sense that even a poorly blended additive is better than nothing. ZDDPlus claims it is completely compatible with all current SM/SN-base stock oils, including synthetics. On ZDDPlus.com, you will find an absolute treasure trove of technical papers that might take the better part of a day to read and digest. I’ve read barely half the papers and am impressed with the research that went into the presentations. The cost of one bottle of ZDDPlus is around $10, which, for a 5-quart oil change, just about doubles the cost of the oil from $10 ($2 each) to $20.00, but this is really cheap insurance, and you don’t have to chase around for boutique or race oil from mail-order houses, where it can cost $5 or more per quart along with a shipping charge. There is a lot more to this story if you really want to get into some technical information about oil, viscosity, base stocks, oil testing, and much more. It’s also important to reiterate that ZDDPlus is intended for vehicles without catalytic converters, as high-zinc and phosphorous levels in the oil will contribute to contaminating a catalytic converter.
So to alleviate your fears about running a flat-tappet camshaft and prevent you from chasing after a hydraulic roller application just for lubrication reasons, I’d say once you have successfully broken in your flat-tappet camshaft by using a high-quality break-in oil from one of the companies we tested in our story, you could use an off-the-shelf API SN oil along with a bottle of ZDDPlus and more than likely your engine will be protected with sufficient levels of zinc and phosphorous. This is not the only solution, but it appears to be one of the most cost efficient.
ConocoPhillips (Kendall); Houston, TX; 877/445-9198; KendallMotorOil.com
ZDDPlus; Burlington NC;336/ 229-5554; ZDDPlus.com