Although the North American passenger car market still uses overhead valve (pushrod) valvetrains, they are very much out of vogue in the rest of the world. While big-capacity, lazy, low-revving engines are common in the US, where gasoline is relatively inexpensive, small-capacity, higher-revving engines are used where gasoline is more costly. Small engines power small cars, and these require less fuel. Higher-revving engines are a challenge for the valvetrain, and the overhead cam engines...
Modern race engines place very harsh demands on valve seats for a number of reasons, all of which are concerned with extracting the absolute maximum from the engine. In comparison to a passenger car engine, as an example, racing seats are expected to deal with a greater amount of heat transfer per unit volume, higher temperatures, greater stresses on valve seating and higher seating velocities. We expect to run thin seat areas in order to improve gas flow characteristics at a given valve...
Some engine components are generally ‘out of the limelight’ as far as coverage in motorsport publications are concerned. Race Engine Technology magazine and these RET-Monitor articles tend to cover most items in detail, so you can find articles covering the most minor of components. Valve locks (collets, or cotters if you prefer) and lash caps (valve shims) are among those we cover, and are among the smallest and lightest parts in a race engine. Like me, you may be surprised to...
In race engines that contain them, the valve spring is the most highly stressed component. In the best springs, the materials, heat treatments, hardening processes, manufacturing techniques and surface treatments combine to allow them to operate at incredible levels of stress. If they are of the best quality, correctly installed and operating within calculated limits then valve springs are very reliable; they fail because they are either over-stressed due to driver error (over-revs on down...
Pushrod engines are ‘old hat’, an anachronism in these modern times, but while the rest of the world has moved on and adopted the overhead camshaft, the users of big V8 engines have remained loyal to the old tech. That is probably an opinion shared by many engineers who have never had any dealings with pushrod valvetrains. The fact is that there are countries – the US and Australia for example – where cheap gasoline makes daily motoring with a big engine...