Did you know Super Late Model fan belts slip twice on every lap?

Did you know Super Late Model fan belts slip twice on every lap?

By Fergus Ogilvy: To prove or disprove it, simply examine the coating on the water pump and crank pulleys. If the coating on the working surfaces has vanished, the belt is slipping—probably chronically. Most Super Late Models, in common with IMCA Modifieds, encounter belt slippage every lap as the engine instantly decelerates on each straightaway, resulting in fan deceleration from around 7,800 to 3,500rpm—a tumultuous event that erupts during a period of one to two seconds. Pump and pulley maker KRC knew that replacing the GM 4-blade fan was unrealistic, but a more effective belt arrangement might resolve the problem. So they collaborated with belt manufacturer Continental, which has resulted in a new 10-rib belt and pulley assembly (PN: KIT16122600) that offers 100 percent more surface contact than previously available. Importantly, the new 10-rib belt is constructed with Kevlar cords and unlike the Gatorback, dispenses with the familiar cross-cut in the interest of greater belt strength. “Driving the fan has not been the problem,” says KRC’s Ken Roper, “slowing it down in an instant is the cause of belt slippage and belt stretch. The deceleration forces are usually more than a five- or six-rib serpentine belt system can control. Belt slippage and belt stretch are the most prominent causes of belt replacement.” Installation of the new 10-rib assembly is also an enlightening process. The crank pulley features a rectangular slot at its center and works in conjunction with an R-lok mechanism. The R-lok is a concentric, triangular interlocking innovation that accommodates a pulley, or a stack of pulleys that operate precisely on a common center. For further instructions and...
Flatness: How gas ports and flat ring grooves succeed with lightweight racing rings

Flatness: How gas ports and flat ring grooves succeed with lightweight racing rings

By Sam Logan: A great many modern drag racing engines are equipped with lightweight piston rings. These rings require combustion pressures delivered through gas ports to achieve complete ring seal. Horizontal gas ports are used in oval track racing pistons to avoid carbon ingress while vertical gas ports are the preserve of the drag racing engine. In either case, the gas ports direct pressure downward and behind the ring to seal the ring to the bottom surface of the ring groove and also to force it outward and seal its thin outer perimeter face to the cylinder wall. To achieve this, it is essential to decide the correct diameter of gas port and to allocate the correct number of gas ports and to equally space them around the piston. Harnessing gas volume and evenness of pressure to a flat ring groove and flat piston ring accomplishes cylinder seal. “So, the number of gas ports, times their diameter creates a volume number,” explains Gibtec’s Robbie Giebas. “On smaller pistons we reduce the diameter of the gas ports and increase their number. To prevent flutter, pressure must be evenly dispersed around the ring. “Also the advent of flatter rings and ring grooves means you can run tighter ring-to-groove tolerances—often as close as 0.0004in to 0.0005in. A decade ago tolerances were significantly greater, probably twice this amount.” Having functional gas ports and perfectly flat rings and ring grooves—with tolerances of 0.00005in to 0.0001in—promote effective ring sealing. But also this sequence of events relies on the fact that every action is the product of a previous action.   Gibtec Pistons (PRI Booth #501)...
ProMedia Events Announces Chevrolet Performance Challenge Series 2016 Schedule

ProMedia Events Announces Chevrolet Performance Challenge Series 2016 Schedule

Santa Ana, CA (November 17, 2015) – Home of the NMCA Muscle Car Nationals drag racing series and the “World’s Fastest Street Cars”, ProMedia Events is pleased to announce the 2016 schedule for the Chevrolet Performance Challenge Series. This all-GM series features purpose-built race cars and street-legal cars equipped with Chevrolet LS and modern LT powerplants such as 5th Gen Camaros, C5 Corvettes, Z28 Camaros, late-model Firebirds and GTOs. With 2016 marking the 10th Anniversary of the original LSX Shootout, the four events on schedule for the Chevrolet Performance Challenge Series are the place to be for all racers and enthusiasts of late-model GM-equipped vehicles. “We are thrilled to bring another year of exciting, side-by-side all-GM drag racing to our fans and racers,” said Rollie Miller, ProMedia National Event Director. “This series includes some of the best engineered LSX-powered race cars in the country. They’re events that Chevrolet fans don’t want to miss. The Chevrolet Performance Challenge Series will run at the following events in 2016. Each event features classes for all levels of participants including Drag Radial, Real Street, Chevrolet Performance Stock, Street King, Rumble and True Street:     June 3-5, 2016 5th Annual Chevrolet Performance Nationals Presented by Scoggin-Dickey Parts Center Atlanta Dragway – Commerce, Georgia   June 23-26, 2016 15th Annual NMCA All-American Nationals Featuring the 10th Annual Chevrolet Performance LSX Shootout Lucas Oil Raceway at Indianapolis – Indianapolis, Indiana   August 25-28, 2016 15th Annual NMCA World Street Finals Summit Motorsports Park – Norwalk, Ohio   September 9-11, 2016 7th Annual Holley LS Fest Beech Bend Raceway Park – Bowling Green, Kentucky   Since...
NHRA rule changes introduce new era of Pro Stock optimism

NHRA rule changes introduce new era of Pro Stock optimism

By Titus Bloom: NHRA’s Pro Stock drag racing class is a magnet for those enchanted by naturally aspirated race engines—it’s another name for engineering excellence. Not for them the recipe of forced induction or easier routes to greater power. Now the 2016 rule changes adopted for Pro Stock will shortly sweep aside several significant long-held traditions in an attempt to modernize the acclaimed 500cu in formula and conserve its resources. So we asked Robbie Giebas of Gibtec Pistons about the state of play so far. Giebas, who has been at the heart of the game, making racing pistons for Pro Stock engines since 2003 and an early advocate for billet designs, acknowledged that piston work will soon begin. But to get a broader perspective of developments currently being pursued, he directed us to Bob Reinhardt, head of MadCap Racing Engines of Lakewood, Colorado. “The principal differences in Pro Stock for 2016 are not difficult to understand,” says Reinhardt, “the carburetors and hood scoop have been abandoned in favor of electronic fuel injection and a less prominent air collection system. Most importantly engine speeds have been reduced to a maximum of 10,500rpm.” For the longer term health of the division, NHRA’s new rules might save some competitors from themselves. With each passing year, tens of thousands of dollars were spent on testing the latest carburetor tweak and, clearly, next year’s rules will end this expenditure forthwith. And also, specifying a throttle body, multi-point injectors, ECU, and even the exact location of the injectors in the runners will avert further expensive development. You know how this goes—lured by Formula One technology...
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