DOHC better then SOHC?

[Fredrick_NP]

Someone was telling me that the dual cams have more power but SOHC have less to break so they are more reliable. Is that true? Does it really make that much of a difference?

Im looking at a 2001 Dodge Stratus coupe with a Mitsubishi 3.0L SOHC, and a 2004 Stratus with a Chrysler 2.7L DOHC. They both have the same HP, but I wonder how reliable the engines are.

I would rather have the american engine, but the older 2.7L seemed to have some problem... (although people say the newer ones fixed the problems) and being DOHC, wouldnt that make it even more likely to break?

[MagicRat]

Neither of those 2 engines are exactly brilliant, but the 2.7 definitely has problems.
Surprisingly enough, the Chrysler 3.2 and 3.5 liter V6 engines are DOHC and are very reliable.

Generally speaking DOHC engines produce a bit more power and are more expensive to manufacture and repair.
But as far as reliability goes, this is more dependent on the design and the use and maitenance its seen than on basic valvetrain layout.

[beef_bourito]

dohc has the potential to provide with better top end power and sohc with better low end torque, it's not a huge difference on a street car but if you're building a racecar it is a big enough deal.

[Black Lotus]

Originally Posted by beef_bourito

and sohc with better low end torque,

Wrong, explain yourself.

[Schister66]

go search Honda VTEC engines and you'll find that both engines are reliable, but the DOHC will beat a SOHC up and down all day long!

A SOHC D16Y8 is the stock Civic Vtec engine, but the EM1 (Si) DOHC B16A2 has the same displacement and is also a Vtec engine...it gets better gas mileage, has more power and is just as reliable as the SOHC.

I have a 99 GSR w/ a B18C DOHC VTEC engine and i've had a D16Y8 Civic, but i don't think that i'd ever go back...I get more gas mileage, have more power and a lot more possibility for power than the Civic. My opinion is that DOHC engines are much better than SOHC!

[Reed]

in general sohc engine have less moving parts so less moving parts at low end provides better torque, dohc engine have more flow potential therefore they have more power at top end. in general

[MagicRat]

Originally Posted by Black Lotus

Wrong, explain yourself.

with respect, beef burrito is on the right track here.
Most DOHC engines are 4 valve per cylinder.
Most SOHYC engines are 2 valve.

Compared to a SOHC engine, a DOHC 4 valve engine has lower valve train mass per valvespring and can rev higher. The larger port area is better suited to high rpm use. Engine designers can and often do get maximum benefit from these traits by allowing camshaft profiles with more lift and duration that favours maximum volumetric efficiency at high rpm, over the SOHC design.

Of course, this does not apply to all DOHC engines, because the engineers may have different design parameters for certain engines and may not choose to tune a DOHC engine this way.

[beef_bourito]

thank you for responding for me, i was going to say something like that but didn't have time to post it first.

[ec437]

This isn't exactly relevant to the question, but I just though I'd brag a little bit: I used to have a QOHC engine

[drdisque]

you had 4 camshafts per bank of cylinders?

[Polygon]

You can't say that one is more reliable than the other. There are SOHC engines that have 4 valves per cylinder. You're better off with DOHC for performance in my opinion. It is simple, airflow equals power and DOHC engines have more airflow. Ah, but I just said that there are SOHC engines with 4 valves per cylinder, why not just get one of those?

Two words, valve overlap. Want to tune your engine? You can tune the valve overlap much better and easier in a DOHC engine.

If you're concerned about reliability there are other things you need to be looking at.