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Piston strength wins races

pistonsThe colours may have changed from red to blue (Budweiser to Copart) at Kenny Bernstein Racing, but the objective never alters. The objective is to build bullet-proof engines that can go down the 1000-foot dragstrip quicker and faster than the car in the other lane.

For co-crew chiefs Rob Flynn, Mike Guger and Todd Smith (who came over from Don Prudhomme's Snake Racing after that outfit closed operations at the end of the 2009 season), the objective is to fit the strongest piston available.

"I don't think we want to make the piston lighter; we need to make it stronger more than anything so that it supports our crankshaft," Flynn confirmed. "We want it to maintain its shape," and running close to 8000 horsepower doesn't help a piston's service life.

The Bernstein trust works with both Venolia and JE pistons, depending on the application. "Everybody's combination is a little bit different but with most combinations, you usually have to watch the No. 3 piston. In the nitro motor, the piston is just not strong enough. You don't get much life out of it, so we have them in for 1-2 runs per piston, but No. 3 is susceptible [to failure] because of the distribution of air and fuel," added Smith. "Still, you can't necessarily build a specific piston to deal with strength for that hole, because you don't want to mess up your balance. That's the hardest running one, for us anyway."

Flynn acknowledged the team has "scuffing in the skirts sometimes, and you do have problems with cracking ring lands. That's just a by-product of the pressures that we put into the cylinder." Guger added, "It sinks the dome. We use a flat-top piston and we sink the domes with all of our pressure."

Even if the manufacturers - who furnish aluminium forged material for these pistons - make the part thicker, it doesn't help. "You can add material and still sink it," Flynn told me. "I think if you make it too thick, you'd lose some of the heat properties that you want to keep in the chamber."

"It's a fine line really," Smith noted. "Many piston manufacturers will play with the forging that is specific to them. We just try to relay to them what we see or what we need and they'll go about it accordingly."

Flynn said he gives his primary manufacturer a specific piston to copy "and they made it the way their material works with our ring configuration and our compression height. We have a different compression height - everybody's a little bit different," he said. "What we are doing is different than what others have and we don't worry too much about what the other guys are doing. We just do our own thing," which is the way the entire paddock operations in NHRA Top Fuel racing.

Thus far in the season, the Bernstein gang has had trouble going rounds - until Gainesville, when they made it as far as the quarterfinals. Flynn, Guger and Smith can see the changes they've made are starting to pay some dividends.

Fig. 1 - Kenny Bernstein Racing is looking for strength in its pistons, not light weight

Words and photo by Anne Proffit

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