|
|
NHRA Legal Stock Eliminator 283 Chevy - Class EngineInside a Successful NHRA Stock Eliminator Chevy September 07, 2012 By Steve Dulcich Photography by Wade Owens
|
|
On the dyno at BES, the little... On the dyno at BES, the little engine pumped out 373 hp, a very impressive number considering the small displacement and very restrictive class rules. Constant testing and trying different components is the key to gaining ground in NHRA's tough Stock Eliminator class. Building an engine for a street performance or bracket race application leaves the builder wide open in terms of parts selection, with power potential only limited by how far you are willing to go and how much you are willing to spend. In NHRA-legal class racing, such as within the ranks of Stock Eliminator, the game rules are strictly defned. The rule book will dictate major parts, from legal major castings to limitations on all manner of engine specifcations. These rules and limitations have their roots in OEM passenger car combinations, as offered by the factory, with mandated use of a variety of OEM components or their legal replacements. As such, a Stock Eliminator competitor must work within these constraints while competing for the prestige of a successful NHRA class racer. Wade Owens of Cape Girardeau, Missouri, jumped into the highly competitive world of Stock Eliminator running a 283 small-block-equipped '66 Chevelle in L/Stock Automatic. Through honing his skills and refning the small-displacement Chevrolet engine, Wade's combination has become one of the most competitive in the game. What intrigues us about the Stock class cars is the on-track performance and engine power output obtained within the strict rules constraint. A mid-11-seond Chevelle would be an accomplishment to be proud of with a big-inch small-block sporting the latest high-performance parts. What is amazing about a Stock Eliminator car like Wade's is that this level of performance is achieved with a small-displacement engine through stock small-valve OEM heads, a factory iron intake, and the tiny, virtually antique, OEM carburetor. The Bow Tie block gets a tedious... The Bow Tie block gets a tedious makeover in the lower end. Hours are spent smoothing and deburring to cut down on windage. Notice the crankcase pressure balance holes ported into the bottom of the cylinders. They allow the pressure in the cylinders to escape into the next bay, helping with the downstroke motion. How is it possible? The name of the game in NHRA Stock racing is an incredible level of refnement in getting the most out of the combination. Testing, optimizing, and thinking outside the box are the hallmarks of a successful effort in this category of racing. On the surface of it, one would be hard pressed to believe that a Stock 283 Chevy, with an actual displacement of 293 cubes, breathing through 1.72-inch intake valves, with lift restricted to a meager 0.399 inch through a stock-style valve train would pull hard to upwards of 8,000 rpm and deliver power approaching 1.3 hp per cubic inch. Wade recently had his small-block apart for a freshen-up and contacted us to see if we would be interested in having a look at what's inside. We took that opportunity and detail just what is important in making one of these combinations work. It is no small achievement to put together a competitive combination at a national level in a venue as tough as NHRA Stock Eliminator. With the help of the likes of multiple Amsoil Engine Masters Challenge champion Tony Bischoff of BES Racing and other dedicated professionals, Wade Owens has done just that. A stock GM crankshaft is required... A stock GM crankshaft is required by the strict NHRA rules. Allowed modifications are a normal balance job, a maximum stroke allowance of plus 0.015, shot-peening, and a deburr. The crankshaft in Wade's engine measures 3.013 inches and has had the balance holes welded closed for a smooth counterweight contour. Into the Class Racing Fray
Why would anyone want to run Stock Eliminator? Arguably, the most competitive class in the sportsman ranks, these racers are a special breed. In Stock, you have to use an engine and transmission that was factory available. NHRA designates how much the cars will weigh based on a horsepower factor and shipping weight. Wade Owens relates his introduction to the ranks of Stock Eliminator, "When we frst built the Chevelle, we had no idea it would make a great class car. I had some 283 parts and always liked the '66 Chevelles." Wade and his son, Alex, attended their frst race with the car in 2007. Wade tells us, "It was pretty fast right out of the box. That just stoked us up to see how fast we could really go." And fast they are. The Chevelle currently runs right on or just under the national record. "It takes a lot of work to get the car to run 1 second under the NHRA index. You have to be willing to test everything, then test some more. Sometimes our test sessions are successful, other times, not so much. Carburetors and intake manifolds are not created equal. Casting variances can mean as much as 10 hp difference. It pays to keep your best piece until you get one that shows an e.t. gain." It also pays to surround yourself with a great support team, and Wade is quick to share credit: "Guys like Tony Bischoff of BES, Michael at ICE Ignition, Jeff with Canton Products, and Dean Oliver of Deano's Carburetors have all contributed big to the Chevelle's performance." As of this writing, the car has garnered eight class wins and six No. 1 qualifying positions and has run as fast as 11.571 in L/Stock Automatic. So what's next? Wade is always contemplating ways of going quicker, "We still have plenty of things that I wonder if it will work. Alex always says it's gotta be worth something!"  NHRA also mandates the use...  NHRA also mandates the use of a spec piston. These Ross pistons are coated with a Calico CT-3 skirt coating to help reduce piston-to-wall friction. The Trend pins are stock diameter and weigh in at 80 grams. Manley small-journal rods are box stock and a welcome upgrade over the stock rod. The assembly has a minimum weight of 1,195 grams.  The rings are one of the key...  The rings are one of the key components to raising the horsepower. Wade has tried no less than six different sets of rings trying to gain an advantage. The piston's ring lands must remain stock, but the ring pack can consist of anything. A gas-ported spacer with a 1.2mm ring rides in the top, while a back-cut napier is used as a second ring. The oil rings have been set to 12 pounds of pull. This ring combination along with a perfect hone produces zero percent leakage.  The valves are supplied by...  The valves are supplied by Victory and undergo major surgery by the guys at BES. Valve diameter is constrained by the rules and measures 1.72 inches intake and 1.50 inches exhaust as used in the 283. Although Wade prefers not to divulge the back-cuts or seat angles, suffice it to say they have been flowed extensively to find a combination that gains every advantage within the rules.  PAC Racing Springs and retainers...  PAC Racing Springs and retainers sit on Comp Cams seat locators. Wade tells us these springs are very reliable and hold their load very well. He sets them up at around 200 pounds on the seat, which generates about 400 pounds over the nose.  At the time of this writing,...  At the time of this writing, Crane ball fulcrum rockers are still being used. They have been deburred, lightened, and tumbled for stress relief. Roller rockers are allowed starting in the '12 season.  Cliff Sherman provides Wade...  Cliff Sherman provides Wade with these trick lifters. They feature a tool steel foot and have been shimmed up to allow only 0.012 inch of plunge in the hydraulic mechanism. In Stock Eliminator, if your particular engine combination came with a hydraulic lifter, it must bleed oil from the oil orifice when checked by the NHRA tech.  Deck height is carefully set...  Deck height is carefully set to ensure maximum compression. Wade runs a tight 0.031-inch piston-to- head clearance. A 0.040-inch Cometic head gasket coupled with a 0.009 positive piston placement results in a 10.6:1 compression ratio.  No stone can be left unturned...  No stone can be left unturned on these engines. Perfect alignment of the cam and crank gears allows the timing chain to turn without binding. Every horsepower counts with these very restrictive rules.  In Stock Eliminator, class-legal...  In Stock Eliminator, class-legal cylinder heads and allowable modifications are severely restricted. Many hours on the flow bench time are required to optimize the castings within the confines of the rules and the limited valve lift allowed. Prep to these GM 520T castings was performed by the guys at BES Racing Engines.  Chamber modifications are...  Chamber modifications are not allowed, and for Wade's combination, the minimum volume is limited to 54.9 cc. In Stock, intake and exhaust runner modifications are also illegal. On the 283, port volume is limited to a maximum of 140 cc intake and 60 cc exhaust. Under the rule constraints, the flow numbers over 170 cfm on the intake and 140 cfm on the exhaust require considerable expertise.  A close-up of the crank scraper...  A close-up of the crank scraper reveals two pieces of sheetmetal sandwiching a strip of Teflon. These are carefully cut so the crank and rods actually rub against them. After the engine runs for a short time, it becomes a "zero" interference fit. Even with the low viscosity racing oils, this scraper arrangement still shows an improvement on the track.  A custom-made windage screen...  A custom-made windage screen is used and helps to control the hurricane that occurs inside the pan. Many different styles have been tried and several others are in the works. You have to keep trying new things to try to stay in front of the competition.  A factory, unmodified, iron...  A factory, unmodified, iron intake is required. The 283 came with a No. 457 intake, but somewhere along the way, a typo was made allowing a No. 459 intake to become legal. The No. 459 was a 300hp intake and is worth about 8 hp over the No. 457.  Michael Konstandinou of the...  Michael Konstandinou of the Australian-based ICE Ignition supplied Wade with the firepower. This is a new ignition box for 2012 and features adjustable timing curves. The crew at BES is no stranger to using ICE products. They have won all their Engine Masters Challenge championships with this style of ignition.  Probably not your first choice...  Probably not your first choice for a performance carburetor, the Rochester 4GC or 4 jet is rated at 486 cfm. The carb has been extensively reworked by Dean Oliver of Stuttgart, Arkansas, to feed the 283. It must remain stock on the bore and throttle plate size. This is one of the areas the NHRA tech officials scrutinize with a fine-toothed comb.  There are very few areas in...  There are very few areas in Stock Eliminator where you can "one-up" your competition. Any internal oil pan modifications are welcome; traps, baffles, scrapers, or trays are all permitted. You have to be willing to test constantly to see what your combination responds to. Wade tells us there is big power here if you can find it.  The oil pumps are also modified...  The oil pumps are also modified to reduce drag and friction, and Wade only uses pumps from Larry Stewart of Clinton, Mississippi. These modified pumps feature cut-down gears and a pair of anticavitation spacers. These pumps are dyno tested and have shown a solid 6hp advantage over conventional pumps. Lots of testing is required to tweak the oil pressure to the desired psi with the thin weight oils often found in Stock.  It doesn't look like a high-rpm...  It doesn't look like a high-rpm race valvetrain from this vantage point, but rest assured, it has been coaxed to release every available horsepower. This valvetrain is stable and tested to 7,700 rpm.  The latest camshaft was supplied...  The latest camshaft was supplied by John Partridge and the guys at Bullet Cams. The exact specs are top secret, but Wade does disclose that the duration measures approximately 258/260 degrees at 0.050 inch, while lift for this engine combination is rules-limited to 0.399 inch, measured at the retainer. Wade has tried the 4-7 firing order swap camshaft but found it to run identical times as a conventional cam. Some guys are using large core 50mm and 55mm camshafts, too. According to Wade, the jury is still out on whether it's worth the extra expense on a NHRA Stocker. VITAL SPECIFICATIONS:
NHRA LEGAL STOCK ELIMINATOR 283 CHEVY
BORE - 3.935 INCHES
STROKE - 3.013 INCHES
DISPLACEMENT - 293.1 CID
COMPRESSION RATIO - 10.6:1
CAMSHAFT - BULLET HYDRAULIC FLAT-TAPPET
CAM DURATION - 258/260 DEGREES AT 0.050
VALVE LIFT - 0.399 INCH
ROCKER ARMS - CRANE BALL PIVOT STAMPED STEEL
ROCKER RATIO - 1.5:1
LOBE SEPARATION - 106 DEGREES
INSTALLED CENTERLINE - 102 DEGREES
TOP RING - TOTAL SEAL 1.2MM GAPLESS
SECOND RING - TOTAL SEAL NAPIER
OIL RING - TOTAL SEAL LOW-TENSION
PISTONS - ROSS STOCK LEGAL
BLOCK - 305 GM BOW TIE
CRANKSHAFT - BULLET GM
CONNECTING RODS - MANLEY 5.7-INCH SMALL JOURNAL
CYLINDER HEADS - GM IRON NO. 520T
INTAKE VALVE DIAMETER - 1.72 INCHES
EXHAUST VALVE DIAMETER - 1.5 INCHES
INTAKE MANIFOLD - GM IRON NO. 459 DUAL-PLANE
CARBURETOR - ROCHESTER 4GC
HEADERS - DENNIS REEVES 15/8-13/4 STEP
IGNITION - ICE IGNITION
DAMPER - ATI ON THE DYNO
NHRA LEGAL STOCK ELIMINATOR 283 CHEVY
TESTED ON VP C-11 FUEL
TEST AT BES RACING ENGINES
| RPM | TQ | HP
| | 5,000 | 342 | 326 |
| 5,100 | 338 | 328 |
| 5,200 | 335 | 331 |
| 5,300 | 333 | 336 |
| 5,400 | 332 | 341 |
| 5,500 | 331 | 346 |
| 5,600 | 329 | 351 |
| 5,700 | 326 | 354 |
| 5,800 | 324 | 358 |
| 5,900 | 321 | 361 |
| 6,000 | 318 | 363 |
| 6,100 | 315 | 366 |
| 6,200 | 312 | 368 |
| 6,300 | 308 | 369 |
| 6,400 | 305 | 371 |
| 6,500 | 301 | 373 |
| 6,600 | 296 | 372 |
| 6,700 | 290 | 371 |
| 6,800 | 286 | 370 |
| 6,900 | 281 | 369 |
| 7,000 | 276 | 368 |
| 7,100 | 271 | 367 |
| 7,200 | 266 | 364 |
| 7,300 | 259 | 361 |
| 7,400 | 254 | 358 |
| 7,500 | 248 | 354 |
| 7,600 | 241 | 349 |
| 7,700 | 234 | 343 |
| 7,800 | 227 | 338 |
| 7,900 | 220 | 331 |
| 8,000 | 213 | 325 |
|
|
|