So a buddy of mine were talking (bench racing to be exact) about the differences between the cam in a V8, a SOHC, and a DOHC. Being that both of us know nothing about cars (I know I'm not mechanically inclined, but I'm not confident in his either) and we both agreed we didn't know what the differences were between an engine with 1 cam and another engine with 2 or more cams. Is there really any significant difference in something we're not seeing/understanding, or is there no actual gains worth taking seriously? Thanks in advance guys....

EDIT: This thread has been answered and has been found to be OT. Thread is officially closed and end of discussion.


Modified by Breaker00 at 11:04 PM 2/10/2006

 

well it just depends on the motor, some sohc have the same horsepower of motors that are dohc. as for v8s motors with more cams usually have more hp. also im kinda stabbing in the dark because i only own one v8 and its not in a car... YET!

plus this is the wrong forum so prepare for others to flame.

also i dont really understand the question, a sohc engine is a completely different then a dohc engine. of course there are power differences.

 

http://auto.howstuffworks.com/camshaft.htm

...come back after you've read that.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AJxr &raquo;</TD></TR><TR><TD CLASS="quote">

also i dont really understand the question, a sohc engine is a completely different then a dohc engine. of course there are power differences.</TD></TR></TABLE>

Same here

 

The question is way too broad to answer with a good answer.

It's basically like asking:

"Is a V6 better than a 4 cylinder?"

There are too many variables to answer that. I'd say a Honda 1.8L VTEC 4 cylinder is better than some old V6 found in a ford pick-up truck, but there are plenty of V6 engines such as the C32A 3.2L VTEC V6 found in the NSX that makes more power than a 1.8L VTEC 4 cylinder.

See the point?

Now the question as it relates to HONDAS?

Most people will say the DOHC engines are better, and on the whole I agree because they do make more power in stock trim. Now this in itself is a highly debated topic on Honda message boards, and I personally own a semi-built SOHC engine and have owned numerous DOHC VTEC engines, so I'm not a DOHC **** by any means.

 

Here's how I see it. If you look at your typical V8, you have a single cam in the block that opens valves via pushrods. This setup is cheap and makes for a compact engine. But that's about it in terms of advantages. Pushrod wells vie for the same space in the head casting as the intake ports. This means less than ideal intake porting. Also, the mass of the valve/rocker/pushrod/lifter is VERY high compared to the mass of an OHC valvetrain. This means that (1) heavy springs are required, which increases friction, and (2) the valvetrain cannot respond well at high RPMs. For these reasons, this type of valvetrain is generally only used on engines that are sufficiently large in displacement that they can make good power despite all the disadvantages of this sort of valvetrain.

But things get trickier when it comes to SOHC vs DOHC. DOHC is somewhat better in the high RPMs due to the lighter rocker arms. DOHC is really the only feasible way to go if you want VTEC on the intake AND exhaust valves since there would just be too many lobes on one cam if you tried to do this with SOHC. And DOHC has the advantage of being able to independently tune the intake and exhaust cams (a whole new cam would be needed with SOHC, on the other hand, to change lobe separation). On the other hand, SOHC does not have the same detrimental effect on intake porting as pushrods, though. And when compared to pushrods, the difference in valvetrain mass between SOHC and DOHC is really not that great. However, when it comes specifically to Honda, DOHC motors are more suited to high performance applications for reasons above and beyond just the cam configuration. For instance, DOHC Honda heads breathe better than SOHC Honda heads. This has nothing to do specifically with the fact that they are DOHC. It is just that these are Honda's more performance-oriented engines. So Honda given them better porting.

 

Matt- That was most definately the answer(s) I was looking for. Seeing as how my buddy is a musclecar V-8 fanatic that claims they are perfect in every form and shape over any 4 cylinder import on the market, it helps to be reassured that Honda's DOHC design isn't some kind of "foreign" mistake. Sad to say, but I work with the guy and there is no convincing him that imports have the speed and can do equal to a V-8 in the times on a strip. Thankfully, I can return to work and be more confident in my own motor to still compete against his car (85 Firebird w/ 350 bored 60 over making it a "410") this summer, and deal with more of his BS for a few months longer knowing what you said. Again, thanks for the info.

Also, I do apologise for having put this thread up and not posting this in the proper forum section as I was not aware there was a whole other section not specified for specific cars. Having gotten my answer and found this to be OT, I'll now end this thread on my own.