OHV vs SOHC

[F1GT]

The cylinder heads for OHCs are also bigger because of the more complicated mechanicals. They usually have 4valves/cyl., so they breathe better and can rev higher. So the power is usually up higher than OHV. Cost more to make, like V6Bob said. The higher an engine can rev the better. This one reason why engines like Honda seem to have a lot of horsepower. Because they produce their power up high. Torque X RPM/5252 = HP so the higher the RPM the torque is produced the higher the HP figures.

This is one of the reasons why the LS1 is so amazing, because it can breathe pretty well up high and is willing to rev, behaving more towards the OHC side.

OHV is design more for around town and has a fixed valve duration, unlike many of todays OHCs with variable valve duration. So the cam in an OHV engine is design for around town, and can't breathe as well up high because the valves aren't opening long enough, like ALL the iterations of the Citation's V6(2.8,3.1, and 3.4 - 3.5 coming out soon, then 3.9 next yr.). If they increase the duration then, the low end power would go out the door. So they choose low end power because thats more of where the majority of the driving is. This is why VTEC was invented and why now there is I-VTEC. So the duration can change along with the increase RPMS. Rather than a fixed duration through out the rev range.

[ April 12, 2003: Message edited by: F1GT ]</p>

[HAZ-Matt]

<blockquote>quote:</font><hr>Originally posted by F1GT:
The cylinder heads for OHCs are also bigger because of the more complicated mechanicals....<hr></blockquote>

And this is one of the most important aspects of OHV versus OHC. You can fit an engine of greater displacement in the same size engine bay using OHV. Or you can opt to reduce height, and in turn decrease the height of the nose of the vehicle, decreasing frontal area and drag.

[unleaded]

that is true a ohc engine takes up more room in the engine bay. A lot of people(especially in the import world) think that ohv engines arn't as good as ohc, but in reality it is all about the purpose you use them for. Also i have heard of and ohv engine gm has designed allowing the use of variable valve timing. When i look at engines i like i don't have a set rule as to what kind is better i just look at each one and the characteristics, then judge it. LIke the viper v10. Sure it is an ohv engine but i like it way better than almost any ohc engine. the old viper engine redlined at like 5k but it still smoked about every car that redlined at 8k.

[WickEdSix9838]

my Toyota 22R was a SOHC and only two valves per cylinder too!!