OHV vs OHC, difference? Benefits?

[SS1970chrysler]

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.

Early 80's Ford Escorts used the "cam-in-head" setup initially.

 

[Silk]

What engine was that ? We didn't get Escorts in the '80's, we moved to the Mazda platform. But some did get here, and I had an '87 van, but took the Kent based diesel out and fitted a 1600 Kent. I've seen the Kent based engines and the OHC engine in these Escorts, and the diesels of course, but no cam in head.

 

[swalve]

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.


The 3.0L Mitsubishi engine that was in a lot of Dodges used that design- the cam was in the middle of the head, and there were rocker arms that actuated the valves on either side of it.

True overhead cam design means the cam directly pushes down on the valve. I think.

 

[OVERKILL]

Originally Posted By: swalve
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.


The 3.0L Mitsubishi engine that was in a lot of Dodges used that design- the cam was in the middle of the head, and there were rocker arms that actuated the valves on either side of it.

True overhead cam design means the cam directly pushes down on the valve. I think.


No, that's SOHC, similar to Ford's setup in the Modular.

 

[asand1]

Originally Posted By: swalve

True overhead cam design means the cam directly pushes down on the valve. I think.
Like the 22R in my earlier post.

 

[OVERKILL]

If the camshaft is above the head, it is overhead cam, IE the cam, is overhead, or over the head. It doesn't matter if it acts directly on buckets, uses HLA's and roller rockers.....etc.

 

[TFB1]

Originally Posted By: Silk
What engine was that ? We didn't get Escorts in the '80's, we moved to the Mazda platform. But some did get here, and I had an '87 van, but took the Kent based diesel out and fitted a 1600 Kent. I've seen the Kent based engines and the OHC engine in these Escorts, and the diesels of course, but no cam in head.


Cutaway of Fords CVH 4cyl Escort engine...

Cam in head, lifters ride on cam and operate the rocker directly with no push rod... Early versions were interference and bent valves if belt failed, within a couple years they were modified to be a non-interference engine by providing additional valve to piston clearance...


http://mechdb.com/index.php/Ford_CVH_engines

 

[yonyon]

Originally Posted By: TFB1
Originally Posted By: Silk
What engine was that ? We didn't get Escorts in the '80's, we moved to the Mazda platform. But some did get here, and I had an '87 van, but took the Kent based diesel out and fitted a 1600 Kent. I've seen the Kent based engines and the OHC engine in these Escorts, and the diesels of course, but no cam in head.


Cutaway of Fords CVH 4cyl Escort engine...

Cam in head, lifters ride on cam and operate the rocker directly with no push rod... Early versions were interference and bent valves if belt failed, within a couple years they were modified to be a non-interference engine by providing additional valve to piston clearance...


http://mechdb.com/index.php/Ford_CVH_engines


Yeah, functionally a SOHC engine but not technically so due to the construction. This is the sort of thing that can happen if you demand that engineers come up with "something new" on short notice and on penalty of being force-fed LSD until they comply.

 

[Silk]

Originally Posted By: TFB1

Cutaway of Fords CVH 4cyl Escort engine...


No, that's just an ohc. In the BMW and Honda designs the cam sits low on the side of the head, at the level of the ports, and uses short pushrods. Being of single cyl design (BMW has a single cyl on each side) the ports are front and back, so the cam doesn't get in the way of porting, the Honda is a single cyl of course. At the time (1994) there were pictures in all the magazines of the revolutionary BMW design, but can't seem to find a picture on the internet yet.