Understanding hydraulic valve lifters

Understanding hydraulic valve lifters

By: Ray T. Bohacz: I have a love-hate relationship with valve-lash adjustment. I love adjusting anything mechanical: getting my hands on it and fine tuning it to perfection. The part I dislike about lash or free play adjustment is its awkwardness and complexity. Too many components have to be removed to perform a ten-minute task. For this reason, I like engines with hydraulic valve lifters that, for the most part, require no adjustment. However, when adjustment is necessary, instead of setting lash, as you would with solid or mechanical valve lifters, a hydraulic system requires preload as there is no lash. This is usually required only when the cylinder head is being reinstalled. The need for lash or free play The camshaft is responsible for the valve’s timing and its lift as well as its duration—the periods it remains open and closed. In a cam-in-block engine, this is accomplished by the camshaft working with intermediate components: valve lifter (or tappet), pushrod, and rocker arm. With an overhead cam design, the intermediate components differ, using some style of follower in lieu of a pushrod and possibly a tappet. This discussion focuses on the hydraulic tappet employed in cam-in-block engines. It’s the profile of the camshaft lobe that determines the valve action, and that motion is first transmitted to the valve lifter and onto the pushrod and finally the rocker arm that contacts the stem of the valve. When the parts are cold, they shrink and as heat is generated they expand. For this reason, free play is required to prevent parts binding when heated. Free play is created between the...
Misunderstandings about intercoolers and carbureted superchargers

Misunderstandings about intercoolers and carbureted superchargers

By Chris Beardsley:   Unlike port fuel injection systems, carburetors have a unique advantage while operating on boosted engines without an intercooler. In carbureted applications, the air charge from the supercharger is significantly warmer than ambient air. When warmer air is forced through a carburetor, the *vaporization process is enhanced as the cool fuel mixes with it. Ever try starting your carbureted engine in the dead of winter? Now compare that to a hot August afternoon. The warmer air of the supercharger blowing through the carburetor amplifies the vaporization process. The result of superior vaporization is a cooler, denser air charge under pressure. The warmer air mixing through the carburetor does something else just before it cools. The heat acting on the fuel causes the fuel particles to disperse—a chemical explosive process that sends fuel in every direction with violent force. When this occurs at the entrance to the plenum, each intake runner is filled with a more evenly balanced mixture of fuel and air that enters the cylinders. Naturally, cylinder-to-cylinder distribution affects horsepower. For these reasons, the ample performance of carburetors incorporated in boosted projects without an intercooler is evident. Even common pump fuels generate impressive power, and increasing ignition timing can further the power potential using these principles. “But intercooling is better,” I hear you say. “What if I add one of those?” While intercoolers have their place in boosted performance, for most carbureted applications adding an intercooler works against you. It looks fantastic and its associated plumbing enriches any engine compartment. But, by directing the air charge through an intercooler to feed the carburetor, we lose...
Androwick: 17 Pro Stock wins, new circle track heads & 2-pc intake manifolds for small-blocks

Androwick: 17 Pro Stock wins, new circle track heads & 2-pc intake manifolds for small-blocks

By Archie Bosman:   The first air-flow specialist I watched at work was Mike Androwick Sr.  A Pennsylvania native, he had plied his trade successfully in Pro Stock racing with Larry Morgan before moving to North Carolina in 2005. Finding efficient air flow in intake manifolds and cylinder heads and then skillfully uniting it with well-judged valve train technology is a mysterious art. Yet these are the achievements of the Androwicks: father and son, Mike Jr. Now three seasons with Gray Motorsports, they dominated NHRA Pro Stock in 2018, winning the US Nationals at Indy, the championship title with Tanner Gray and powering Drew Skillman to third in points. Remarkably, over the past two seasons, Gray Motorsports recorded 17 wins and 10 runner-up finishes. For the most part, Mike’s Racing Heads (MRH) has operated in two prominent arenas: NHRA Pro Stock and Circle Track. The big-block-powered Super DIRT series in the northeast remains a strong market for MRH, yielding 7 track champions in 2018. This year, however, with promoter Bret Deyo initiating the Short Track Super Series (STSS), MRH has introduced new cylinder heads and intake manifolds for Chevrolet small-blocks. The heads adopt valve angles of 10, 11, and 13 degrees, and the intakes are offered as two-piece billet aluminum assemblies and available in different versions for different heads. MRH has also enjoyed increasing success in Dirt Modified and Dirt Late Model categories. Currently situated just south of the I-85 in Concord, NC, they are moving this month to new facilities 7 miles away. Find them at: Mike’s Racing Heads 10 St. Charles Ave. NE Concord, NC 28025 Mikesracingheads.com...
Goodwood victory: exploiting the potential of a V-12

Goodwood victory: exploiting the potential of a V-12

By Freddie Heaney:   On September 12, on his 67th birthday, race engine builder Bob Bartlett of V&B Engines of Chatham, Virginia, provided sufficient motive power for Joe Colasacco to win the Glover Trophy at the 2018 Goodwood Revival. Driving John Surtees’ 1964 F1 championship-winning Ferrari 1512, Colasacco drove the race of his life, defeating former Nissan works Touring Car driver Andy Middlehurst in Jim Clark’s 1963 F1 championship-winning Lotus 25. ‘We are proud to have contributed to this effort,’ wrote Bartlett, who not only built Joe’s winning engine but also supplied his cast magnesium wheels and other drivetrain parts. ‘Obviously, we were pleased to hear Middlehurst complain about his 20 HP deficit to our engine (although we don’t think it’s actually that much).’ Nonetheless, it was a crowning achievement. You can also take delight in the unique high-pitched howl of the Ferrari heard at times during race coverage. Watch the race at https://www.motorsport.com/ca/vintage/video/goodwood-revival-sunday/373338/ and fast-forward the video to 6:25:05 to see the prelude, or move along a further 12mins to enjoy the race. Two further points, first, pay attention to Belleville, Illinois racer James King driving the no. 22 Brabham BT7, the ex Dan Gurney car that won the French GP. Second, for those unfamiliar with the incomparable Goodwood Revival and its protocol, all participants and spectators are encouraged to dress in period; that is, Goodwood’s heyday from 1948 to the...