[Patrick Norris]

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.

 

[Patrick Norris]

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.

 

[Patrick Norris]

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.

 

[Patrick Norris]

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?