All engines use camshafts to control the timing of the valves opening and closing. That is, all but the rotory engine. This is where the scam starts to take effect. Overhead Cams have been around as long as the engine itself. So it had Overhead Cams, no big deal. What has always been played up is the number of valves. The number and location of the cam shaft(s) has little to do with how much air can enter and exit the cylinder head. It's the valves and overall design of the head that determines this. So why is it that every ad over the last several years brags about Overhead cams?

It's nothing new for companies to use buzz words to attract buyers. Often times these words have strong appeal for a few years then eventually fade out with the use of a new word. I'm sure you will remember the terms Auto Reverse and Stereo. At one time these were terms everyone looked for. Now almost all of the respected products have these features, so it's not that big a deal. Unfortunately, the term Overhead Cam may become one of these terms that becomes obsolete simply because all engines would become this type, sort of like Stereo. Until then it will continue to be a misleading term that is far over used.

As with everything, there are good and bad aspects in the use of Overhead Cams. On the good side they offer the "potential" for higher performance. I must stress the term "potential" because if this potential isn't used it's no better than if it weren't used. The potential performance gains can be increased rpm range, greater efficiency, and more overall power. The increased efficiency and higher rpm comes from the fact that there are fewer moving valve train parts, and thus less moving mass. Without the use of Overhead Cams, an engine must use pushrods. These pushrods offer increased valve train mass and instability. This isn't to say that pushrods can't work well, just that they have limits. The increased power from Overhead cams comes from the ability to control more valves. Most modern small displacement performance engines use "dual" Overhead Cams that typically control four valves per cylinder. Without a doubt, a four valve per cylinder head will have the ability to flow more than a two valve head of the same design. Again, most of this is potential and almost all of the performance comes from the addition of more valves per cylinder, and not simply the use of the Overhead cams.

With the good must come the bad. The down sides of the overhead cam design are increased and awkward maintenance, occasional larger size, and all too often higher costs. Maintenance can be a huge issue. Anyone with an Overhead Cam engine will know what I'm talking about. They typically need work every 50,000 to 60,000 miles. I'm not saying that they need major work, just routine maintenance. This can involve timing belt / chain replacement and valve train adjustment. Unfortunately if these things aren't done on time they can (and too often do) cause serious and costly engine failure. For the Overhead crowd, this will be a relatively costly repair. Most pushrod motors on the other hand, are very forgiving and can often go for well over 100,000 miles before they need only a timing chain replacement. For the pushrod crowd this will typically be a cheap fix. Most Overhead cam engines are very difficult to work on. Much of this comes from their occasionally larger size. A lot of this also comes from the way engines are simply cramped in most modern cars. Most Overhead cam engines cost more to produce than pushrod engines. Some of this comes from the higher complexity and sensitivity of these engines. Some of it comes from lower production numbers. Even if none of these down sides existed, if the potential of the Overhead cam isn't used it will be of no use.

The best place get an idea of how much potential is in an Overhead Cam engine is in Formula 1 racing. These cars are the highest form of automotive technology available. Their small displacement Overhead Cam engines can rev to over 17,000 rpm and make over 800 horse power. This is truly amazing performance, especially from less than three liters. At the same time, the pushrod engine should not be overlooked. In Indy car racing (CART, not IRL) the Buick pushrod V-6 has been doing battle with the highest technology Overhead cam engines from Mercedes, Ford / Cosworth, Chevy, Infinity, Oldsmobile, and Honda. Over the years, the fastest most powerful engine to be in the Indy 500 was the little pushrod engine. It wasn't technology that was setting records, it was the shear power of a well designed engine. Other examples of pushrod power can be found in the world's most powerful engines found in Drag Racing. These pushrod powerhouses can produce well over 6000 hp. They don't spin too much over 9000 rpm, but their absolute power can't be matched by any current Overhead cam engines. So again, the potential is just that, potential. There is a lot to be said for a good design, regardless of how much Technology goes into it.

A perfect example of lost potential in an Overhead cam engine is found in Ford's new 4.6 liter engine - that is when compared to the 5.0 liter pushrod engine it replaced. The comparison between the two engines must start with their size. The Ford 5.0 was often considered a "large" small block engine. Often when people would put together old Ford street rods, they would use Chevy engines because they were shorter. This being said, the new 4.6, even though it's smaller in displacement, is much larger in physical size. This new engine just barely fits in the cars that the old 5.0 easily fit into. This makes both maintenance and upgrading much more difficult, if at all possible, but more on that later. This large overall size must also be difficult to design around, which makes me wonder how these things happen in the first place.

One of the most important issues between the two engines is their performance. The new engine is said to be efficient and high revving. I guess they never really brag about the actual power anymore. The old 5.0 made understandably more power, but not by much. While this "rated" power is almost the same, the actual feel of the two engines is somewhat different. Even though everyone brags about the high rpm power of the 4.6, the 5.0 is typically much faster. On the Dyno, though, the truth that the 4.6 doesn't really make power into higher rpm's any more than the old 5.0 did actually comes out. Throw on some aftermarket parts and the differences increase. For far less money, the 5.0 is a much more powerful engine.

Now we are back to the upgradeability. Obviously the old 5.0 has far greater aftermarket support. It's been around for a really long time. The thing to notice though is the fact that most of the 5.0's support has come in the last few years. The 4.6 has now been around for a few years now and has little to no support, unless all you want is an air filter and an exhaust system. The lack of support for the 4.6 isn't limited to aftermarket either, Ford itself has done very little for their new engine. The lack of interest goes all the way to the track. No one uses the 4.6 for any type of racing. Ford does win races, but with the old pushrod and not the Overhead cam. There is said to be a lot of potential in the Cobra "dual" Overhead cam engine, but again, no one wants to look for it, especially at it's high price. If there is potential, it may never be found. The 5.0 on the other hand continues to amaze people with many street cars well over 500 hp, and many race cars well over 1000 hp. Without a doubt, the Ford 5.0 is now the most supported aftermarket engine, and will probably stay that way for a long time.

In the end, the SOHC 4.6 has gained neither mileage nor power. It costs more to produce, maintain, and upgrade. Simply put, there are no advantages to this engine. The engine it replaced was very well accepted. So why was the 4.6 built? It was a very poor decision for Ford to stop using the old pushrod engine. If they had stepped up production on their Cobra pushrod engine they would have had a cheaper, more powerful, user friendly, and reliable engine. It would have fit more cars and people (owners) would have been much happier. The 4.6 is the perfect example of lost potential and a poor design, mostly due to lack of testing prior to its release. Customers should not have been the ones to do Ford's testing. I personally blame the automotive industry and especially magazines like Motor Trend for these new low performance engines. If you read the reviews of these new cars you will easily see what I mean. "We love the new engine. It was about time Ford got up to date." In my opinion, it's no longer a performance issue but instead a technology issue.

It's a shame because I feel it will eventually mean the end of the factory Hot Rod. If you look at Dodge you will see just what I'm talking about. Dodge used to make a lot of powerful cars that people could afford. Now the only thing they have to offer is the Viper. Not only can very few afford one, but there are few made and little aftermarket support. What happened to their Hot Rods? Well, it appears they turned into Foreign designed front wheel drive grocery getters. While these cars are fine under their original Mitsubishi label, it's the loss of their pushrod rear wheel drive Hot Rods that is a true loss. It's a shame because we are soon to lose Ford to this same problem. Ford admits they want to eventually change all of their cars over to front wheel drive and Overhead cams. No more Mustang or Thunderbird, at least not as we know them. So much for tradition and common sense. Why hasn't the unbelievable success of the Fox body (5.0) Mustang and it's connection with the aftermarket proven to the automakers just exactly what people really want is beyond me.

While I may have gotten off course, the main point of this whole thing is to show that the use of the Overhead cam is no guarantee of performance. It is all too often an indicator of an auto maker going in the wrong direction just to keep up with its competition and to please the wrong people. Good press is looked at much better today than good performance. Until people begin to speak up, the auto makers will continue to go in the wrong direction and, in the end, we will all lose. A quick trip to ANY local dealership will prove that cars are no longer designed to be what people want to buy, but what auto makers want to build. Look at the interiors. Cup holders are always there, but usually can't hold any drinks. Again, all that they are after are buzz words and not real solutions. It only takes a little bit of thought, but hopefully people will start to notice - and speak up.