The advantages of the DOHC engine over that of the SOHC lie directly in the placement of the cams. Due to cam position, the DOHC design allows the spark plug to be placed directly in the middle of the combustion chamber (optimal regardless of what you may say above). Also, due to the cams laying directly over the valve train, valve duration can be minimized due to better float prevention and thus enabling a higher rev limit (a large reason you see DOHC not SOHC in F1 motors).

Now as far as your B-series vs. D-series debate goes, it all depends on how far the person wants to go in messing with the engine. Myself, I went with a B18C5, not because of the "hype" as you like to put it, but due to the completeness of the package. I was able to get a transmission with great gearing, stock LSD, more displacement over a d-series, internal and external oil cooling, strong internals (well as strong as OEM cast can be considered), moderately aggressive cam grinds, and a great head. All that was required was for me to bolt it in and go hit some road courses. With a D-series motor, while I don't doubt I could make the same power, it would require quite a bit more time and effort. To each his own I suppose.

 

Bill, in regards to sparkplug placement, you are wrong. The SOHC placement is superior and allows for a more efficient combustion. There is a significant power loss with a centralized plug (especially with domed pistons) and the charge burn can be hindered upon combustion.

With the right valve springs, valvefloat will hardly be an issue. I would be more concerned with the stroke and piston speeds.

BTW, I didn't bring up the F1 car example, matraca112 did.

 

hey i am just here to see what is the best engine to go with what i am looking for in my car.and the more everyone brings things up the more everyone can learn. but i will say this both DOHC and SOHC must have there pros ands cons. so it just ends up being a personal pick.

 

Umm...again I disagree.

While valvefloat can be addressed by stiffer springs, this in turn increases frictional losses as well as increasing valve-train wear. DOHC offers the better solution.

As far as the plug placement is concerned, there's a reason that the plug is angled and not centered, it's due to a cam sitting directly overtop. While I'm sure placement is ideal for the situation, it is not overall ideal. Regarding higher piston domes, yes, they do present more impedence for the flame front than that of lower domed pistons. However, this can be countered by advancing the timing. Couple this with the benefit of centrally located plugs (enable less advance) and you have a decent workaround.

But don't take my word for it. Below is the result of a quick google search. Please find me some information supporting your side, preferably more than one or two sources from BBS posts.

 

Bill, most of your examples and links there are for mass productions lines (Ford, NSX, GM). These are not 9 second drag cars, and they are not manufactured to run upwards of 14:1 compression. My information comes from Bisimoto who has built many drag cars like this. You will not find his information published on any website you find on Google.