What is the difference between the Overhead Valve and Overhead Cam engines, in layman's terms? What are the advantages/disadvantages of one over the other?
OHV vs OHC, difference? Benefits?
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About 100 years difference in technology.
Ohc has fewer parts
Originally Posted By: Chris142
Ohc has fewer parts
But it some cases more seals and longer timing chains. Also ohc has been around as longer as ohv
Ohc has fewer parts
But it some cases more seals and longer timing chains. Also ohc has been around as longer as ohv
Originally Posted By: abycat
About 100 years difference in technology.
older than ya think!....http://en.m.wikipedia.org/wiki/Overhead_camshaft
About 100 years difference in technology.
older than ya think!....http://en.m.wikipedia.org/wiki/Overhead_camshaft
OHV is a more compact, typically more robust, lower maintenance system, but does not like revving(more reciprocating masses to control) and having more moving parts, has more drag.
OHC is mechanically simpler, and stands up to high RPM use better, but that long timing belt/chain needs attention a lot more frequently. Furthermore a OHC engine is huge compared to its OHV counterpart.
Its just a matter of what trade off you want to take, GM uses OHV in the Corvette ZR1 and it keeps up with DOHC Ferraris just fine.
OHC is mechanically simpler, and stands up to high RPM use better, but that long timing belt/chain needs attention a lot more frequently. Furthermore a OHC engine is huge compared to its OHV counterpart.
Its just a matter of what trade off you want to take, GM uses OHV in the Corvette ZR1 and it keeps up with DOHC Ferraris just fine.
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Mainly packaging and ease of maintenance. OHV is smaller than OHC when getting into engines with V configurations. There are fewer timing components in a OHV engine since the camshaft can be located nearby the crank, simplifying the design of the chain or belt that is used to keep the engine in time.
When talking about an inline engine, OHC engines can be made quite small and have simpler valvetrain layouts since the cam can actuate the valves directly without the need for rocker arms.
OHC in general is easier to do things like variable valve timing on since the cams are not as space-restricted on top of the engine as they are when buried above the crank. Although VVT is currently doable (and has been done in a production capacity) in an OHV engine.
Technically speaking, an OHC engine is an OHV engine with the cam closer to the valves.
When talking about an inline engine, OHC engines can be made quite small and have simpler valvetrain layouts since the cam can actuate the valves directly without the need for rocker arms.
OHC in general is easier to do things like variable valve timing on since the cams are not as space-restricted on top of the engine as they are when buried above the crank. Although VVT is currently doable (and has been done in a production capacity) in an OHV engine.
Technically speaking, an OHC engine is an OHV engine with the cam closer to the valves.
Originally Posted By: default
OHV is a more compact, typically more robust, lower maintenance system, but does not like revving(more reciprocating masses to control) and having more moving parts, has more drag.
OHC is mechanically simpler, and stands up to high RPM use better, but that long timing belt/chain needs attention a lot more frequently. Furthermore a OHC engine is huge compared to its OHV counterpart.
and OHV is huge compared to 2 cycles and flathead engines....
Makes one wonder how much taller the next evolution in engines will be.
OHV is a more compact, typically more robust, lower maintenance system, but does not like revving(more reciprocating masses to control) and having more moving parts, has more drag.
OHC is mechanically simpler, and stands up to high RPM use better, but that long timing belt/chain needs attention a lot more frequently. Furthermore a OHC engine is huge compared to its OHV counterpart.
and OHV is huge compared to 2 cycles and flathead engines....
Makes one wonder how much taller the next evolution in engines will be.
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In the beginning there was the L head (flat head) engine. It is still common in low end lawn mowers. Both the cam and valves are located in the engine block.
A Ford Flathead V8 Engine Block
Then came the F head but who cares.
Then the Over Head Valve engines came. OHV engines have the camshaft located in the engine block with push rods actuating rocker arms, in turn opening the valves that are located in the head.
Chevy 350
Over Head Cam engines locate the cams in the heads and they run directly over the valves, or can also incorporate rockers.
Nissan VQ30
Toyota 22R
Then came the F head but who cares.
Then the Over Head Valve engines came. OHV engines have the camshaft located in the engine block with push rods actuating rocker arms, in turn opening the valves that are located in the head.
Chevy 350
Over Head Cam engines locate the cams in the heads and they run directly over the valves, or can also incorporate rockers.
Nissan VQ30
Toyota 22R
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Dusenberg was using OHC engines in the 1920s
I assume my 65 Mustang with a 289 was a OHV.
I think the last time we had this discussion one of our smarter members figured out that an ohc engine has 20% less drag to spin the entire assembly.
I forget the actual % number so don't take the 20% as gospel.
I forget the actual % number so don't take the 20% as gospel.
All OHC cam engines have valves in the cylinder head (overhead valves), so technically all OHC are OHV. However, the abbreviation "OHV" is typically used to denote a cam in block engine that uses push rods and isn't intended to include OHC engines.
The only reason why people swap Chevy LS engines into Miatas and such.
Then there is cam in head - BMW motorcycles and Honda ATV, not sure if any cars use it. The cam is low in the cyl head and operates the valves with very short pushrods. Same height as an OHV engine, with cam drive slightly shorter than OHC.
ls1mike
$50 Site Donor 2024
Originally Posted By: Silk
Then there is cam in head - BMW motorcycles and Honda ATV, not sure if any cars use it. The cam is low in the cyl head and operates the valves with very short pushrods. Same height as an OHV engine, with cam drive slightly shorter than OHC.
Interesting. I wonder if there is any advantage to this design.
Then there is cam in head - BMW motorcycles and Honda ATV, not sure if any cars use it. The cam is low in the cyl head and operates the valves with very short pushrods. Same height as an OHV engine, with cam drive slightly shorter than OHC.
Interesting. I wonder if there is any advantage to this design.
Originally Posted By: ls1mike
I wonder if there is any advantage to this design.
Engine height - with the BMW, an OHC engine would be much wider, reducing cornering clearance. Much like Subaru, have a look at the old pushrod engine, then compare to the OHC versions. With the Honda ATV a higher engine means less fuel tank.
I wonder if there is any advantage to this design.
Engine height - with the BMW, an OHC engine would be much wider, reducing cornering clearance. Much like Subaru, have a look at the old pushrod engine, then compare to the OHC versions. With the Honda ATV a higher engine means less fuel tank.
Originally Posted By: abycat
About 100 years difference in technology.
Yeah...OHV engines came much later!
Seriously...
DOHC, 4 valve per cylinder engines? Try 1912...and it was a Peugeot...Bugatti built it before he started his own car company...
About 100 years difference in technology.
Yeah...OHV engines came much later!
Seriously...
DOHC, 4 valve per cylinder engines? Try 1912...and it was a Peugeot...Bugatti built it before he started his own car company...
i have been driving OHV engines since 1965. i see no reason to change, they have done every thing i ask.
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