THE SHOP

Performance & Hotrod Business - Mar. '15

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52 n Performance & Hotrod Business n March 2015 HOTROD car with the unburned oil that's coming out of the exhaust." For similar reasons, hot rod professionals and DIY-ers alike need to pay close atten- tion to the ring packages that come with rotating assembly kits and crate engines. "Is the ring pack optimized for how you want to use the engine?" Jones asks. "Does it have the durability and longevity that you want? If you put in a ring package that's half the thickness of the stock rings, just because you can, then you're going to have problems. You have to make sure the parts you are buying are right for what you are doing." Ring gap can be another issue with a street-performance engine—especially with forced induction. "With a normally aspirated small-block Chevy, you could drive around all day with a ring end gap of 0.016 or 0.018, even though at running temperature that gap may have closed to just 0.002 or 0.003," Jones continues. "But if you add forced induction or nitrous—say a turbo set to 10 pounds boost, which is not uncom- mon today—that same engine may need a 0.030 end gap. So for that 1 percent of the time when you're mashing it to the floor and making big power, the ring has adequate room to grow. Because if those ring ends come together and butt, it will light up the engine faster than you can shut it down. But now, when you're just rolling down the highway to your favorite cruise spot, that 0.030 gap is going to allow a whole lot of blow-by." A simple solution is a gapless piston ring of the kind that Total Seal manufac- tures, where the gap is blocked by a sec- ondary "rail" that has a gap that is turned 180 degrees relative to the gap in the main ring. "You can gap it for the worst-case sce- nario—you can set it at 0.050—and the little thin ring still blocks off the gap in the main ring. So it still draws harder on the intake stroke, eliminates blow-by, and eliminates contamination of the oil. It's the perfect solution for street performance with a power adder." Coated For Life At the same time, steel rings with a PVD coating can significantly extend the life of an engine. "The wear-ability of those coatings is fantastic," Jones believes. "If you're old enough, you remember the days when you had 75,000 miles on your Ford or Chevy, and you said, 'man, I need to start saving my money, because this thing is near dead.' Now you aren't saying that until 275,000 miles. And that's not only because of the engine management systems; it's because of coatings, and quality oil, and how all these things act together. "We're already using chrome nitride coatings on our AP line. The old-style moly coatings were softer, and that let dirt embed in the coating. I recently spoke with a customer who builds dirt-track late- model engines, and who has completely replaced moly-coated rings with chrome- nitrided rings. And he was commenting on how good everything looks when the engines come apart. He said he had one engine in the shop that they were not even going to machine; they were going to put in fresh parts and send it out for another season of racing." "The quality of the coatings and mate- rials have improved tremendously," Meza agrees, "and the new standards they have set are the best things that could have hap- pened in these segments." McFarland notes that there are coatings available to address a vast array of issues— many of which are of little concern to the average performance enthusiast. "The most commonly used and widely beneficial coatings are those that increase overall durability. Reducing drag and therefore wear typically increases durabil- ity, along with ensuring that the piston will perform at its optimum level over the life of the engine," he says. And on the street, says Urcis, "coatings are like an insurance policy, in that you pay for them, but hope you never need to use them. Their benefits in a properly designed and tuned engine, with properly designed and machined pistons, are very hard to quantify. Usually they only help (and usually only for a short while) if there is a defect in the design of the engine or piston, or in tuning parameters of the engine." Installation & Add-Ons When installing pistons and rings, Urcis also emphasizes leaving "plenty of ring end gap. And make sure the rings are not proud of the grooves." "Make sure the entire engine and build area are clean before assembly," suggests McFarland. "Scrub down the block with hot, soapy water and a medium-bristle brush—including all the galleries. Choose a build area that will not be subject to floating debris. You would be surprised at the number of premature wear issues we see due to assemblies that were not clean." Skirt shapes and pin bores have received a lot of attention recently as part of updated piston designs. (Photo courtesy CP-Carrillo)

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