What's the difference...

I was wondering what the difference is between a pushrod engine and a DOHC/SOHC engine.

There are many differences but the basic ones. In a V8, pushrod engines use one cam to control all teh valves. A SOHC uses one cam in each bank of clyinders so it has a total of two. A DOHC uses two cams per bank of cylinders so it uses a total of four cams. For the most part, pushrod engines are more effiecent than SOHC and DOHC. Pushrods are also phyically smaller than there SOHC and DOHC engines of the same displacement. If you want to know more, ask Texan.

OK, pretend I'm a kid just learning a language and try to explain it again. Also, my '02 BMW 330i uses DOHC. I'm wondering why BMW uses DOHC instead of pushrod. What are the advantages (if any) of DOHC. Thanks and bear with me. :) :) :)

Overhead cams are more efficient than pushrod engines. The reason being that OHC has fewer moving parts. Generally speaking, OHC are able to rev higher when compared to pushrod engines. Personally, I wouldn't purchase a BMW unless it had DOHC! A DOHC setup is capable of higher performance than a SOCH or pushrod engines.

Yes, I know this is a 3+ year old thread, but I'm a newb and couldn't resist.

BMW no longer uses pushrod engines in their cars because BMW is about performance and pushrods aren't. There are infinate variables, but OHCs are typically more powerfull and they can run higher RPMs. Enginerd, actually the pushrod design has fewer moving parts and is generally smaller, lighter and cheaper than an OHC equivalent. Just take a look at an old VW air-cooled engine and then a 1990+ Subaru engine. Both are flat fours, but the Subaru SOHC and DOHCs are maybe 6 inches wider and a few inches taller. It's an overall inferior design, but it does have it's advantages, such as better torque in low RPMs.

If your going to drag up a 3 year old thread covering a topic that has been done to death in several other threads since, at least think of something new and useful to add to the discussion please.