How to Become an Indispensable Clutch Man

By Sam Logan:   It’s no secret that the modern day racing clutch has morphed into a pretty significant piece of engineering. Of course, all that became possible thanks to evolution. In short, constant increases in horsepower, ongoing trends in tire technology, nitrous oxide developments, better superchargers, and that all-important “need for speed” are responsible for wholesale changes in clutch design and application. Single-disc street-type clutches gave way to multiple-disc units, while at the same time clutch facing (or friction) materials went through a whole series of upgrades and changes over the years. You know the story – nothing stays the same in life. We thought it would be interesting to shed some light on just how these clutches operate in the intense arena of PDRA competition – namely, in the highly competitive world of Pro Nitrous and Extreme Pro Stock. In order to do that, we contacted the pros at Ram Clutches, based in Columbia, South Carolina., which seems to be the clutch of choice for many of today’s top racers. Intriguingly, most of these eighth-mile PDRA Pro Stock cars also compete in the MMPSA (Mountain Motor Pro Stock Association) championship, which run twice the distance with little or no changes to their specifications. Similarly eighth-mile PDRA Pro Nitrous cars regularly compete in quarter-mile NHRA Pro Mod events.   Clutch Basics — Pro Nitrous and Extreme Pro Stock Looking at the numbers, there is no minimum weight requirement for Pro Nitrous cars, although they typically weigh in the 2,350 to 2,400 pound range. These cars can trip the 60-foot timers in .950 to .970-seconds and run from 2.55... read more

Power Company I

Kevin Stoa Engine Build part 1 of 3. Text & phots by Sam Logan: By the end of his first year in business Kevin Stoa had built 80 race engines. A twice Super Nationals winner in IMCA Modified, Stoa formed his company in January 2009, on his fortieth birthday, in his home town of Albert Lea, Minnesota. He renovated his shop and hired two trustworthy engine builders he’d known for decades, Preston and Jerry, and KS Engineering was in business. Located near the town’s water tower, the shop curiously displays no name. In fact, callers eager to visit the establishment can stand outside the building at 117 North Newton Avenue in confused silence while inside a dynamometer races at 7,300 rpm—a masterpiece in urban sound suppression. Acclaimed race engine shops usually succeed through the aspirations of one individual, and it’s unlikely there is a single shop of any consequence that is not the lengthened shadow of one man. And so it has been with the able young Stoa. Over the past two seasons KS Engineering’s race engines have demonstrated impressive pace and durability. In 2012, on Memorial Day weekend, four different customers prevailed in four different races. By mid-season the KS order book contained reservations two months ahead. Our interest aroused, we decided to pay a visit and try to document some of the secrets of Stoa’s race engine building techniques. On the dirt ovals Stoa is a much-admired man: quiet and understated he is uncomplicated, direct, and sincere. In the workshop, he has a thorough yet pragmatic approach to his craft, and his deftness around an engine cradle... read more

Power Company II

Kevin Stoa Engine Build part 2 of 3. Text & photos by Sam Logan:   Probably the biggest fallacy about engine power output is the number that reveals its peak power. But it’s a deceit perpetuated by most of us. We run our finger down the page looking for it. The engine builder pursues it because often his job rests upon it, the car owner requires it, and the crew chief desires it—even magazine titles splash it across their covers, using it to entice greater magazine sales. The result is that the racer shopping for an engine almost always inquires of its peak power and the circle is complete: everyone engages in racing dynos.  “In the eighties,” says Keith Wilson of Wilson Manifolds, “when I ported Childress race engines, their star Dale Earnhardt Sr. never cared about peak power. Instead he spoke of feeling it in the seat and dynamometer figures were of little account, he wanted to feel the car accelerate coming off the corner.” Kevin Stoa, the accomplished IMCA Modified racer and engine builder says, “The key in making the car accelerate is to determine its most effective RPM range. If the best oval track engine builder in the world made unrivalled peak horsepower from 8,500 to 9,500rpm, his engine would be beaten every time by another that’s producing its full power from 6,500 to 7,800rpm because it accelerates faster.” Bigger induction runners, for example, will often demonstrate impressive power on the dyno, but under racing conditions they often disappoint with lackluster throttle response. “Dirt track racers make most of their overtaking maneuvers when coming off the... read more

Power Company III

Kevin Stoa Engine Build part 3 of 3. Text & photos by Sam Logan: Let’s say your 400cu in race motor operates under water, like a fluid pump, and with every two revolutions of the crankshaft it would ingest and displace 400 cubic inches of water—receiving it through its intake and discharging it through its exhaust. But when the engine operates with air, especially at high engine speeds and equipped with a small cross-sectional area in the intake ports, it will consume more than its stated displacement. By pulses and resonant tuning and inertia and air speed and all kinds of trickery, the savvy race engine builder knows the more air he can persuade to enter his cylinder the more power he will generate. Carefully, using the cylinder bore as his beginning point, he’ll usually select the largest intake valve he can fit into the combustion chamber, making sure its head is positioned at an appropriate distance from the cylinder wall. Positioning it too close to the wall creates a shrouding effect and impedes the flow of the incoming air. He’ll probably use a valve with a concave head to save weight and he’ll surely consider the optimum compression ratio. The more astute will deliberate on exploiting the advantages of squish or “quench” which accelerates the combustion process. On the compression stroke the air-fuel mixture is squished out from the flat, narrow spaces between the piston and the cylinder head and forms fast-moving jets that agitate the mixture and boost combustion speeds. Intake port volume usually isn’t regarded with as much importance as the smallest cross-sectional area, which accelerates... read more

Installing a new Street Demon

By Sam Logan. Photos by Moore Good Ink. Download text and hi-res images 1 of 2. Download text and hi-res images 2 of 2. Before the new Street Demons were first released to the public on Friday, May 25, 2012, the carburetor company dispatched twenty to thirty pre-production units to discerning carburetor critics for testing and evaluating. For this purpose Street Demons were sent all over the country—even to Australia. Tests were conducted at sea level and in the mountains, in cold and in hot conditions, in stop-go traffic and in engines with unfathomable camshaft timing—profiles contrived for noise rather than power. Some even found their way onto towing vehicles, lugging heavy trailers up hills. All testers were invited to “Have at it,” as they say and were actively encouraged to present their findings—warts and all. One of these pre-production Street Demons appeared at Automotive Service and Performance (ASAP), a hot rod tuning shop in Gainesville, Georgia. Known as the poultry capital of the world, Gainesville nestles in the Appalachian foothills on the shores of Lake Lanier about 50 miles north of Atlanta. It has an elevation of 1250 feet. ASAP’s Bobby Tow had a 1972 Dodge Dart lined-up and awaiting the fitment of the new Street Demon. The Dart, now owned by Rick Ellis, President of the North Georgia Mopar Club, is one of around 250,000 produced in 1972 and was supplied originally with a Carter two-barrel carburetor, which was replaced by an Edelbrock 600 some years ago. Now the Edelbrock is being replaced by one of the first available Street Demons. Here in this sequence of photographs... read more

More handy tuning tips for modular carburetors: Part 2

  Part 2 of 2: By Sam Logan. Download hi-res images and text here. If you ever have the chance to discuss engine tuning troubles with the legendary Jon Kaase, you’ll rejoice in his simple logic. “Most engine troubles,” declares Kaase, “are centered on spark or fuel—if it has the former it is either getting too much or too little of the latter.” In the first part of this series of Handy Tuning Tips, we asserted for the benefit of the young enthusiast that the most valuable attribute of the engine is its production of vacuum.  When the vacuum is applied to the carburetor it draws a fine mixture of air and fuel through its labyrinth of tiny drillings. When the mixture is supplemented by spark and compression the engine acquires perpetual motion. But as Kaase reminds us, the air-fuel mixture must meet the correct proportions. In Handy Tuning Tips Part I, we attempted to give the potential engine tuner a command of the fundamentals. In systematic fashion we discussed the opportunities and potential problems with the idle circuit, particularly the seemingly unending troubles with poorly adjusted transfer slots. We continued with float levels, accelerator pump shooters (nozzles), and air bleeds. We concluded with an illustration of the carburetor’s base plate and identified its leading features. Here in Part II we compare the vacuum secondary-style carburetor with the mechanical secondary model, we explore the reasons for increasing the initial ignition timing, and we examine the essentials of modular carburetor’s metering block. Debunking the myth of selecting carburetor size by formula Using a formula to select carburetor size is a dubious practice.... read more

Flywheels: Attributes that are good to know

by Archie Bosman:   Most high-performance flywheels are created in billet steel or in billet aluminum. The advantage of the billet steel over the original cast iron unit is that, though they weigh the same, usually around 32lbs, the billet steel unit is significantly stronger. Crucially, it remains free of stress cracks and, therefore, safe at high engine speeds and higher clutch clamping forces. In addition billet steel flywheels operate more effectively with modern high-performance clutch friction materials than do their cast-iron counterparts. In comparison, the billet aluminum flywheel has the decisive advantage of carrying minimal weight. Generally it rids itself of half its mass—often tipping the scales at around 16lbs. Lower mass means a lower moment of inertia, which translates to faster response; that is, faster acceleration and deceleration as well as less wheel spin.  Clutch and flywheel maker Ram of Columbia, SC construct their aluminum flywheels from 6061-T6.To avoid distortion they use a 1/4in thick steel insert as a friction surface, which mates with the clutch disc friction surface. To maintain flatness the inserts are fastened to the flywheels by 18 rivets.To overcome clutch snatch or chatter and provide minimal run-out, both steel and aluminum flywheels are Blanchard-ground. The Blanchard grinder contributes a proper friction surface and also ensures the flywheel is ground parallel to the crankshaft mounting flange. In addition, Ram counter-bores the flywheels for button-head cap screws that secure the starter gear ring to the flywheel.Nonetheless, the lightness of the flywheel must be considered in conjunction with the vehicle’s gear ratio and its overall weight. If its gearing is too high and its flywheel too... read more

Kaase’s Top Five: Jon Kaase talks engines

By Archie Bosman. Photos by Moore Good Ink: Jon Kaase’s standing was propelled to the forefront of his craft by winning the annual Engine Masters Challenge four times: 2003, ’04, ’08, and 09. But his reputation as an innovative engine builder had already been established over previous decades. Starting his career with the acclaimed Dyno Don Nicholson in 1977, Kaase was instrumental in winning the NHRA Pro Stock championship of that year. In later years he built engines for over a dozen IHRA Pro Stock championship winners. Today Kaase and his team continue to devote their time to building race engines and hot rod engines for all classes, including those with power-adders. In the following paragraphs Jon Kaase provides some insight into his top five power-plants. From his high performance small-block P-38 Windsor engines to Mountain Motor Pro Stock racing units here are some of his comments:   P-38 “The smallest one is the P-38,” says Jon. “These are cylinder heads that suit the 302 and 351 small-block Windsor engines. Initially, they attracted interest slowly, probably because our introduction was a protracted affair. But after six or nine months, sales began taking off, including many welcome orders from our Australian followers. “Now the P-38 has caught the eye of high performance car makers. In fact, we’re about to release a new shaft-style rocker layout and a revised valve cover.” The principal power gains from Kaase’s P-38, you may recall, were derived from its canted, larger diameter inlet and exhaust valves and improved port velocities. Deeper valve bowls with sweeping short turns in the intake and exhaust tracts were further... read more

The Boss Nine Kaase’s New Boss Nine hemi for street rods and street machines

By Ro McGonegal. Pictures by Moore Good Ink: Long-time Mountain Motor engine master Jon Kaase (Racing Engines, Winder, Georgia) says, “The stock Boss 429 parts were a masterpiece for their time, but slightly weak and difficult to work on. We made every effort [with the Boss Nine] to fix anything that was troublesome or failure prone.” At the end of 2007, Kaase decided to take “the plunge and build all new Boss 429 Ford retrofit heads and related parts. I was betting on the fact that there were other Boss fans and Ford enthusiasts out there that wanted these new parts as badly as I did. Although they’ve only been out for a short while, I’m happy to say that they have been well received and successful in whatever projects they have been used in.” Since build orders for the Boss 429 Mustang NASCAR homologation-specials ceased at 1,358 (859 were built in the spring of ’69; 499 more came to life as 1970 models later that summer), these units are rather scarce. Solving the cylinder block problem was easy. Kaase simply undertook the 429/460 big-block (in iron and aluminum) providing them with cylinder head oil drains in the correct location. The JKRE plan included using OE 460 head gaskets, so the deck surface of the Boss Nine heads is much thicker than the original dimension to provide the necessary clamping force. The Boss 429 was humorously under-rated at 375 horsepower while it probably made closer to 475 at the flywheel and without the parasitic drag of the accessories. The ports were huge, had poor low-speed velocity and didn’t begin to... read more