TECH5 is a regular feature where EngineLabs asks industry leaders five technical questions. This week’s guest is Keith Jones, tech specialist with Total Seal Piston Rings.
EngineLabs: Self-tuning EFI systems are quite popular now, but is there a concern for breaking in a new engine with such a system?
Jones: Most important is that it not be overly rich during the break-in period. This is a very common issue with aftermarket EFI & carbs alike. It’s very important to get a proper air/fuel ratio as fast as possible. The newer systems do perform this fairly quick and are generally not a problem, but at the same time the end user needs to be sure it is correct. Overly rich fuel systems can “fuel wash” the cylinder, and the worst time for this is on a fresh engine.
EngineLabs: Why is there a need for different viscosity break-in oils?
Jones: This is more about the given application. We set bearing clearances differently, depending on the application, and these differences can cause the user to need to use thinner or thicker oil. An example would be an NHRA Pro Stock engine. These are spec’d to use very light “0” weight oils as we don’t want to eat up power trying move the heavier oil. If one were trying to break it in with say a 50wt oil, it may cause bearing damage as the clearances it is set to use may not allow that heavier oil to get to the places it needs to be. Another consideration is the size of the ring. When we use very thin, very light drag rings — like our .7mm rings that we see used in high-end applications like NASCAR and Pro Stock — we need to use a lighter oil. These are very low-drag rings and don’t like heavy oils, such as straight 50wt.
EngineLabs: Describe what happens during an improper break-in?
Jones: What do we consider improper break-in? Are the rings are okay but the cylinder is bad, or is it the other way around? Improper break-in can be a situation where the ring is worn or damaged due to a lack of lubrication to the part usually caused by a fuel wash situation or a tune up that is way off base. The other side is a blow-by or oil-control issue, this is generally a cylinder issue either not straight and round, or cylinder finish is just way off. This generally doesn’t hurt the ring they are doing the best job they can in a bad situation. I’ve seen many engines re-honed to “get it right” and same rings re-installed and it sealed right up.
EngineLabs: What applications are best suited for a 2-ring package, and why?
Jones: Few, These are generally high-rpm, short stroke dry-sump type applications like F1 and similar. The 2nd ring is a dual-purpose ring; it not only helps reduce blow by it is also an oil scraper. When we remove that extra assistance from the scenario everything has to be perfect as we are now asking the top ring to do all the ring sealing and the oil ring to do all the oil control. This can be accomplished but leaves very little area to deviate from perfection — meaning perfect cylinder finish and bore geometry, right amount of piston rock, just the right amount of oil delivery to the cylinder and so on. When we have the 2nd ring in play, it gives us a wider margin for error and allows a builder that may not have that perfect scenario to have a well-sealed engine with a minimal amount of additional friction added. And in some cases, there may minimal benefit. The 2nd ring can add 1-2 pounds tension, depending on its size. But when running in a 2-ring platform, we may have to raise the oil ring tension 3-5 pounds to dry it up. So did we really reduce the friction with the 2-ring setup?
EngineLabs: Heard any great ring stories lately?
Jones: Recently got a call from a well-known builder with a 555ci Super Comp engine who put a new set of the exact same rings that he’d been using all along. Calls me up and says the engine is down 40 horsepower and there’s 8 CFM of blowby. We talked about honing, and break-in and everything’s right on. Then he tells me it was the same piston and that’s when the light went off. When re-ringing an engine, rings and piston grooves are like what camshaft and lifters do to each other. This is a sealing surface. I suggested getting some gauge pins and checking the top ring groove. Turns out the ring groove looked perfect to the naked eye but actually had about .0005-inch taper in the bottom of the land. He was putting a fresh ring with parallel sides into a groove worn only .0005, and now the ring is trying to seal on this little back area of the ring and out front it’s flopping around like a teeter-totter. The builder got a new set of pistons, used those same rings, didn’t touch the cylinder walls — got 1.5 CFM blowby and picked up 40 horsepower. Moral of the story: on rebuilds you have to really check the piston ring lands with gauge pins. The issue is that the groove doesn’t wear even; it ends up like a wedge.