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Heat transfer through valve seats

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In designing a new race engine, or developing an existing one, the management of heat in poppet valves - and the transfer of heat from them - is only one small aspect, but it has an effect on performance and reliability. The subject of hollow poppet valves that are cooled internally through the use of sodium or a similar material has been discussed previously, both in Race Engine Technology magazine and in my RET-Monitor articles. The aim here is to transfer heat from the valve head to the...

Pushrod stiffness

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The pushrod, or overhead valve (OHV), engine has a lot to recommend it in terms of packaging, although it achieves this at the expense of much valvetrain stiffness compared to an overhead cam (OHC) mechanism. One of the least stiff members in the pushrod valvetrain is the pushrod itself. Owing mainly to space constraints, but also possibly to mass targets in a smaller regard, the pushrod is a long slender component whose stiffness can dominate the dynamic behaviour of the whole valvetrain...

Double-spring valve springs for success

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John Force Racing (JFR) is one of the most successful Funny Car teams in the history of the NHRA Full Throttle Drag Racing Series. Understanding that multiple team cars on the track results in successfully shared technology, JFR this year is competing with three drivers - John Force, Robert Hight and Mike Neff. There would have been four, but daughter Ashley Force Hood is taking the year away from competition to give birth to her first child. Neff, the crew chief who helped Gary Scelzi to...

Valve-stem texturing - snake oil or snake skin?

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The matter of ensuring that valve-stem lubrication is sufficient has two main benefits. First, any friction between stem and guide creates energy that is necessarily subtracted from crankshaft output power and converted to heat. Minimising this is clearly a desirable aim. Second, if the lubrication is sufficient, we minimise the rate of wear of the valve guide and valve. There are a number of surface treatments that aim to reduce friction and make the stem less susceptible to wear, and...

Rocker stands and shafts

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The pushrod valvetrain, while having great advantages for engine packaging, has the distinct disadvantage of not having a very direct connection between cam and valve, as is the case with overhead cam (OHC) engines. Even in the case where finger followers with roller bearings are used, the stiffness of the system is higher than is typically the case with an overhead valve (pushrod) system. As has been stated in previous RET-Monitor articles on pushrods, efforts are always being made to...