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Lifters - flat versus roller

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In the RET magazine Focus article on pushrod valvetrains (issue 45, March/April 2010), we looked at the effect of flat tappets in limiting the lift velocity of a direct-acting cam on a lifter. The limitation is exactly the same as that in direct-acting overhead camshaft engines. Textbooks on the subject tell us that the distance of the cam-to-lifter contact from the axis of a flat tappet is proportional to the lift velocity of the cam profile. The exact relationship is shown in...

Does size matter?

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How much valve spring does an engine tuner need to propel 8000 hp down a 1000 ft dragstrip? Is it best to use titanium, or is steel sufficient? And are two springs best, or should there be three? For Bob Vandergriff Jr's C&J Energy Services National Hot Rod Association Top Fuel dragster, this year competing full-time in the Full Throttle Drag Racing Series of 22 events, the choices are predicated on a change to the set-up configuration for the 2011 season. Working to gain reliability...

Heat transfer

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With the dominance of four-stroke engines in racing, and the near-monopoly that poppet valves have in such engines, it is little surprise that these parts have become well developed. While most racing is still based on naturally aspirated engines, it is likely that a much greater proportion of race engines in future will be turbocharged, following the continuing trend in series production engines toward smaller boosted power units. There are compelling reasons for doing this; not only is...