Ohc, Ohv, Abcdefg...
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From: Jackson, MS
Ohc, Ohv, Abcdefg...
As previously stated, I'm new to the world of V-sixes. My explorer has the 4.0 liter OHV (I think). I keep reading, first off, how "anemic" it is (Popular Mechanics article), then how much more power the OHC and SOHC engines have. Personally, I think the OHV engine does pretty good, but I haven't driven anything with either of the other two engines in it. So, here's my questions: What's an OHC? What's an OHV? What's a SOHC? What's a "pushrod" engine? (I've read that one several times, usually when referring to the OHV engine!) What makes each engine different? I'm pretty much a dummy about things like this ( 
), but I'm tryin'!! Too many years driving Powerstrokes! lol.
Somebody please break all this down for me! Thanks.
), but I'm tryin'!! Too many years driving Powerstrokes! lol. Somebody please break all this down for me! Thanks.
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S ingle O ver H ead C am, the cam is on top, above the valves and directly operates them. DUal cams are used when an engine has multiple valves per cylinder.
Overhead valve = pushrod. The cam located inside the engine, operates the valves through the use rods that open and close the valves.
Overhead valve = pushrod. The cam located inside the engine, operates the valves through the use rods that open and close the valves.
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No problem. I have 1 of each. Why they couldnt get more hp out of the ohv I dont know, my brothers 4.8L gm ohv is 270hp, but at least its been reliable. My sohc is new so I cant judge the reliablility yet on that one, but it is smooth.
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From: UT
From what I understand, an OHC engine will generally put out more hp than an "equivalent" OHV engine. On the other hand, OHV engines tend to have a smoother torque curve, and generate peak torque at a lower RPM than an equivalent OHC engine.
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The SOHC has a much higher compression ratio than the OHV, which is the reason for much of the added horsepower. Overhead cams can develop higher horsepower at higher RPMs because of better control of the valves. But there are more parts involved so they are more expensive to build.
Both engines have camshafts, but the cam in the pushrod engine is driven by gears on the camshaft and crankshaft. The pushrods that push the valves ride on the cam. But with an Overhead cam, the camshaft is in the heads and push on the valves directly through lever arms. The overhead camshaft is driven by a belt or chain (the latter is better and used by the Explorer V6 SOHC engine) which is driven by a gear on the crankshaft. On a "V" engine, there will be two heads and each has a camshaft, so there are actually two camshafts in a Ford V6 SOHC engine, versus one in a pushrod.
Both engines have camshafts, but the cam in the pushrod engine is driven by gears on the camshaft and crankshaft. The pushrods that push the valves ride on the cam. But with an Overhead cam, the camshaft is in the heads and push on the valves directly through lever arms. The overhead camshaft is driven by a belt or chain (the latter is better and used by the Explorer V6 SOHC engine) which is driven by a gear on the crankshaft. On a "V" engine, there will be two heads and each has a camshaft, so there are actually two camshafts in a Ford V6 SOHC engine, versus one in a pushrod.
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From: Jackson, MS
Okay, I think I'm beginning to get it, though I'm still going to have to study!! I need a really good mechanic friend who will let me watch/help "tear into" an engine or two so that I can see for myself what's what. The OHC and SOHC generate more horses, and I'm assuming also more torque, but the OHV will generate it's peak torque at lower RPMs, where the "work is done." If I'm screwing this up, somebody stop me!! lol.
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dohc produces more horsepower than all of them because you can tune the intake and exhaust valves sprately meaning yoiu can control valve overlap and etc. i don't like push rods at all it's too old of tech. I for one am glad that ford has trumped gm and got with the rest of the world and went forward with engine design.
Dodge brags about the hemi but in reality the japanese have had hemispherical heads for the longest time. (spark plugs positioned directly on top of the piston.) and that about ohv producing more torque in lower rpm isn't true. Dohc engines can be timed to produced max power or torque at whatever rpm you want. I think if it wasn't for emmisions gm would still be using carbs
Dodge brags about the hemi but in reality the japanese have had hemispherical heads for the longest time. (spark plugs positioned directly on top of the piston.) and that about ohv producing more torque in lower rpm isn't true. Dohc engines can be timed to produced max power or torque at whatever rpm you want. I think if it wasn't for emmisions gm would still be using carbs
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