Ohv

[AEstud]

what is an over head valve man? Like is there any pictures or explanations....duuude...:bandit:

[hermunn123]

OHV is the type of engine where the valve is above the cylinder. this includes pushrod, dohc, sohc, etc. those just tell which kind of OHV engine it is. there pretty much aren't any four stroke engines made that aren't OHV. i'm sure someone can explain it to more detail if you need it.

[AEstud]

Yeah I understand what you're saying, thanks.

[Hudson]

Originally posted by hermunn123
OHV is the type of engine where the valve is above the cylinder. this includes pushrod, dohc, sohc, etc. those just tell which kind of OHV engine it is. there pretty much aren't any four stroke engines made that aren't OHV. i'm sure someone can explain it to more detail if you need it.

There are still some lawn mower and industrial engines that are not OHV.

[hermunn123]

ok. are they four stroke?

[USA Racer]

OHV engines differ to OHC ones.

OHV example: LS1 found in the Corvette

The camshaft is lower. It uses a pushrod to open and close the valve. The pushrod has a valve lifter that is pushed when the cam lube spins making the pushrod push the rocker arm to close the valve and complete a stroke. Then as the camshaft goes on the valve opens. Same cycle.

OHC example: I forgot the engine code but it's the 3.2L cast iron block, alloy heads, inline 6 cylinder found in the BMW Motorsport 3-series, aka M3. But it has dual OHCs.

In a OHC (or DOHC, quad-cam etc.)...

The cam, hense the name is over the head of the engine.
The lube spins and makes the finger follower open and close the valve. These have less moving parts and open/close the valves faster. It let's the engine get more from it's four-strokes by speeding the process up. Incressing RPMs.

I could be wrong though.

[enginerd]

I don't want to sound like a jerk, but don't you mean "lobe" and not "lube"?

[hermunn123]

JERK

[Moppie]

Originally posted by USA Racer

I could be wrong though.

And unforunatly you are.

As was stated at the start of the thread OHV or Over Head Valve is any engine with the vavles located in the head above the compustion chamber. Its has nothing to do with how the valves are operated.

[USA Racer]

Prove me wrong.

I think I'm right.

OHV- over head valve.
OHC- valves are still in the head but the cam is also there. The cam is what is acknoledged in the 'OHC' though.

Yes, in both OHV and OHC's the valves are in the head of the engine but I really don't think OHV and OHC are the same thing or else they probably would just say OHV either way. The fact that the cam it self opens/closes valves instead of a pushrod is reason enough to call it OHC.

What I'm trying to say is that OHV and OHC engines are different. An OHC engine isn't an OHV engine otherwise it wouldn't have the distinction of OH*C*.
Again, prove me wrong (that OHV and OHC are the 'same thing') and I'll shut up.

[Moppie]

*moppie bangs head on table*

I think you answered your own question and proved your self wrong.

OHV stands for OVER HEAD VALVE
Which means exactly what it says. The valves are over the head of the compustion chamber, unlike a side vlave engine which has the valves in the side, or a slide valve which uses a double walled compustion chamber to open the side of it to inlet and exhaust ports.

OHC simply means the cam(s) are also OVER HEAD and in every engine I have seen operate Over Head Valves.
However there is no reason you couldn't have an Over Head Cam shaft operating Side valves, or even slide valves.

As for the reason that you dont see OHV stamped on the side of every car instead of OHC, well its down to the marketing gurus who work for the car manufactors, but my asumption would be it has something to do with the fact that almost every car made since the late 40s has used OHV engines making them pretty common when it became fashionable to put more badges on cars. You might have noticed that as OHC engines become almost standard issue with any new car the use of the DOHC and SOHC badges on cars has lessened. It is becoming old technology and so little is gained by bragging about it.


and just one corection here:

The fact that the cam it self opens/closes valves instead of a pushrod is reason enough to call it OHC.

[/b]
The puch rod does not open the valve, its the Rocker which is actuated by the push rod which has direct contact with the valve.
And very few modern OHC engines use cam lobe to valve contact to open and close the valves, most use some kind of rocker assembly between the two.

[AEstud]

Moppie is right...I researched it.

[Hudson]

Originally posted by hermunn123
ok. are they four stroke?

Yes.

[Hudson]

If you see "OHV" in the specs of a vehicle, this typically means that the engine has the camshaft in the block. While OHC (SOHC or DOHC) engines are over-head valve engines, they aren't typically listed as such and are simply stated as OHC/SOHC/DOHC.

Over-head valve does refer to both types of engines, but "OHV" has come to infer "cam-in-block" design.

[Moppie]

Originally posted by Hudson

Over-head valve does refer to both types of engines, but "OHV" has come to infer "cam-in-block" design.

Nicly put, and a good example of why Marketing managers are not allowed to design cars.