Taurus Car Club of America : Ford Taurus Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
307 Posts
Discussion Starter #1
i kno what DOHC and SOHC are and arent OHC and SOHC the same thing..but what is OHV i kno its in the vulcan and its over head valve but how do the valves go up and down? isnt there a cam?
 

·
Registered
Joined
·
712 Posts
There is one cam near the center of the engine (directly above the crank). Pushrods go to the heads and push up on rocker arms. The rocker arms push the valves down.
 

·
Premium Member
Joined
·
5,359 Posts
Both OHC and OHV have their respective advantages and disadvantages. This is an ongoing debate on many car forums, I tend to prefer OHC/DOHC due to the simpler design availability for a double overhead cam setup, higher revving capabilities (usually) and better power in the high end.
 

·
Premium Member
Joined
·
1,005 Posts
Very good link eCar. I know understand my freqent loose of traction on my Duratec.
. I just don't see why they still make the ohv, other than cost savings.
 

·
Registered
Joined
·
263 Posts
Originally posted by sfblacksel@Jan 14 2004, 06:54 PM
Very good link eCar. I know understand my freqent loose of traction on my Duratec.
. I just don't see why they still make the ohv, other than cost savings.
There are many advantages/disadvantages to both designs but I'm not gonna get into that. What no one said was that not all non OHC engines. I think it was an old Chevy 3.1 that used conventional valves. The lifters actuate the valve directly instead of using rockers. The problem is that they don't work as efficiently. The other major and more obvious would be the Ford Flat Head V8. It's called a flat head because the head was just the cover over the cylinders with the spark plug in it. Most lawn mower engines are not OHV just because the size and simplisity of them but the high tech ones are OHV and the new bigger commercial units have OHC.

So the OHV isn't a antique dinosaur like some people make it out. It is a step up. Then the SOHC then the DOHC as well as Honda having some weird 3 valve hybrid designs in between.

And my personal preference is obviously the OHV just because it works well, it is proven, it is decently efficient without costing too much. Also some of the most popular and best engines are OHV, the Ford 5.0, the chev 5.7, and not to forget the 500+ hp Viper V10.
 

·
Premium Member
Joined
·
569 Posts
Is the reason most OHC engines are higher reving engines than OHV engines because of valve floating in OHV engines? (I'm just wondering)
 

·
Registered
Joined
·
263 Posts
Originally posted by biteableniles@Jan 14 2004, 07:34 PM
Is the reason most OHC engines are higher reving engines than OHV engines because of valve floating in OHV engines? (I'm just wondering)
The reason is less moving parts and no reciprocal action in the valve train. The rocker is a limiting factor in a OHV engine.
 

·
Premium Member
Joined
·
10,022 Posts
OHC engines can rev higher because they don't have as many moving valvetrain parts. The lifters especially can go bad (get bent or fly out of the engine block completely) at high rpms.
 

·
Registered
Joined
·
147 Posts
Most OHC engines are smaller than the OHV engines out there. The mass of the piston and connecting rod is also a limiting item for an engines max rpm in addition to the valve float problem. My motor cycle spins to about 16,000 rpm. It has DOHC's just like my Duratec. The Duratec will only spin to about 6,000 rpm. The pistons on my bike are about 1/3 the size of my Sable. I don't think the Duratec motor spins much higher than the Vulcan, both 3.0's, one OHV, the other DOHC.

About the SOHC and OHC being the same. I think they usually use the SOHC designator when talking about a V motor (two cams, one each head) and the OHC disignator for inline motors.

OHC motors are not a new thing. My '68 Camaro originally came with an Inline 6 cylinder motor, 250 CID with an OHC design. That inline-6 design was an older design than the small block V-8, that was an option in the same car.
 

·
Registered
Joined
·
263 Posts
Originally posted by ken_23434@Jan 14 2004, 08:40 PM
Most OHC engines are smaller than the OHV engines out there. The mass of the piston and connecting rod is also a limiting item for an engines max rpm in addition to the valve float problem. My motor cycle spins to about 16,000 rpm. It has DOHC's just like my Duratec. The Duratec will only spin to about 6,000 rpm. The pistons on my bike are about 1/3 the size of my Sable. I don't think the Duratec motor spins much higher than the Vulcan, both 3.0's, one OHV, the other DOHC.

About the SOHC and OHC being the same. I think they usually use the SOHC designator when talking about a V motor (two cams, one each head) and the OHC disignator for inline motors.

OHC motors are not a new thing. My '68 Camaro originally came with an Inline 6 cylinder motor, 250 CID with an OHC design. That inline-6 design was an older design than the small block V-8, that was an option in the same car.
No offense but this isn't correct. OHC engines are larger then OHV. I believe SHOZ123 posted pics comparing a pushrod engine to a sho v8 and a ford 4.6 dohc. The bottom end is identical in size between a ohv and a ohc but the heads are taller in a dohc and since it is a v is spans wider.

Also ohc has nothing to do with cylinder configuration. It is valvetrain layout. Any engine with the cams in the head is OHC no matter if it is a v6 or a inline 4. And DOHC refers to dual cams in the head so it has an exhaust cam and a intake cam with 2 exhaust valves and 2 intake valves per cylinder. A SOHC engine has one cam per head with 1 valve on the intake and one valve on the exhaust per cylinder.

You can't really compare your motorcycle to your car engine. You didn't state what kind it is but most bikes are 2 cycle which don't have valvetrains at all so there is no limiting factor there. The other factor is number of cylinders. A 1 cylinder bike engine isn't gonna have the reciprocating mass of a multi cylinder car engine.
 

·
Premium Member
Joined
·
9,959 Posts
Originally posted by Patrick Norris@Jan 14 2004, 09:50 PM
You can't really compare your motorcycle to your car engine. You didn't state what kind it is but most bikes are 2 cycle which don't have valvetrains at all so there is no limiting factor there. The other factor is number of cylinders. A 1 cylinder bike engine isn't gonna have the reciprocating mass of a multi cylinder car engine.
Every sportbike I have owned revved above 13,000rpm, was a 4 cycle, 4 cylinder engine, with OHC.

My '98 Honda CBR600F3 has 600cc and runs the 1/4 in 10.93sec. stock.

The 4 cycle sportbike motorcycle engine is the same as any 4 cycle car enigne internally and fundamentally. The main differnce being a much smaller bore and stroke, less mass, higher revs, and very little torque.

You are thinking of 2 cycle dirtbike motors.
 

·
Registered
Joined
·
102 Posts
QUOTE
No offense but this isn't correct. OHC engines are larger then OHV. I believe SHOZ123 posted pics comparing a pushrod engine to a sho v8 and a ford 4.6 dohc. The bottom end is identical in size between a ohv and a ohc but the heads are taller in a dohc and since it is a v is spans wider.

Also ohc has nothing to do with cylinder configuration. It is valvetrain layout. Any engine with the cams in the head is OHC no matter if it is a v6 or a inline 4. And DOHC refers to dual cams in the head so it has an exhaust cam and a intake cam with 2 exhaust valves and 2 intake valves per cylinder. A SOHC engine has one cam per head with 1 valve on the intake and one valve on the exhaust per cylinder.

You can't really compare your motorcycle to your car engine. You didn't state what kind it is but most bikes are 2 cycle which don't have valvetrains at all so there is no limiting factor there. The other factor is number of cylinders. A 1 cylinder bike engine isn't gonna have the reciprocating mass of a multi cylinder car engine.[/b]

Ok are talking about the overall size of the engine is larger or are talking about displacement. because i see ohv engine in larger v-8's some older v-6. and your right the heads are larger on the dohc because of all the cam sprockets.

hey who said honda has a werid 3 valve hey my girl has a sl55 that has 3 valves so ha jk.

and i think hte guy knows along with alot of us that if he says he has a motorcycle with dohc we all probably figure its like a small stroke high reving inline 4 just forget about 2 cycle's no torque for
 

·
Registered
Joined
·
263 Posts
Originally posted by BMWevo600@Jan 15 2004, 02:11 AM
Ok are talking about the overall size of the engine is larger or are talking about displacement. because i see ohv engine in larger v-8's some older v-6. and your right the heads are larger on the dohc because of all the cam sprockets.

hey who said honda has a werid 3 valve hey my girl has a sl55 that has 3 valves so ha jk.

and i think hte guy knows along with alot of us that if he says he has a motorcycle with dohc we all probably figure its like a small stroke high reving inline 4 just forget about 2 cycle's no torque for
Speak english much?
 

·
Registered
Joined
·
147 Posts
When I said most OHV engines are larger, I meant displacement, not physical outside dimensions. The larger the displacement the engine is, generally, the more mass there is reciprocating up and down with the pistons and connecting rods. The stresses involved spinning a 4" diamter piston (Chevy 350) are a lot greater than moving the valves (1.6" largest small block V8 exhaust valve, stock). That was my point on why OHV engines normally do not have the RPM range of the OHV engines.

I would have to disagree that most motorcycles are 2 cycle engines. I cannot think of anyone that make a 2 cycle engine for street bikes. What a pain in the @$$ it would be to have to always carry some 2 cycle oil to mix everytime you filled up. Anyway, I have a 2001 Triumph Sport bike. 600cc, in line 4. Puts out just under 100hp at the tire. Doesn't really make any power under 7000 rpm. Get it to 9K and it really comes alinve.


My comment about SOHC vs OHC was merely that if you have an inline engine, they normally say OHC instead of SOHC.
 

·
Premium Member
Joined
·
9,959 Posts
Originally posted by Patrick Norris+Jan 15 2004, 04:27 PM-->QUOTE (Patrick Norris @ Jan 15 2004, 04:27 PM)
<!--QuoteBegin-BMWevo600
@Jan 15 2004, 02:11 AM


Ok are talking about the overall size of the engine is larger or are talking about displacement. because i see ohv engine in larger v-8's some older v-6. and your right the heads are larger on the dohc because of all the cam sprockets.

hey who said honda has a werid 3 valve hey my girl has a sl55 that has 3 valves so ha jk.

and i think hte guy knows along with alot of us that if he says he has a motorcycle  with dohc we all probably figure its like a small stroke high reving inline 4 just forget about 2 cycle's no torque for
Speak english much?
[/b]


I was thinking the same thing.
 

·
Registered
Joined
·
102 Posts
QUOTE
spridget Posted on Jan 16 2004, 02:23 AM
  QUOTE (Patrick Norris @ Jan 15 2004, 04:27 PM)
QUOTE (BMWevo600 @ Jan 15 2004, 02:11 AM)


Ok are talking about the overall size of the engine is larger or are talking about displacement. because i see ohv engine in larger v-8's some older v-6. and your right the heads are larger on the dohc because of all the cam sprockets.

hey who said honda has a werid 3 valve hey my girl has a sl55 that has 3 valves so ha jk.

and i think hte guy knows along with alot of us that if he says he has a motorcycle  with dohc we all probably figure its like a small stroke high reving inline 4 just forget about 2 cycle's no torque for 


Speak english much? 




I was thinking the same thing. [/b]
hey did u see the time i said that 2:11 A.M. After driving around and playing with ZO6's and porsche's and all thoughs people who are all stock and think they are the king of the road, all night takes a beating to the brian. hey its 2:11 A.M. agian hmm i see a pattern
 
1 - 18 of 18 Posts
Top