so im looking thru http://www.fordvehicles.com/cars/mus...eatures/specs/ at the stang gt....and i notice this...4.6L OHV 24V V8...is that a typo or what? i thought they were SOHC or am i mistaken? :shock:

 

Should be SOHC.

 

It is an SOHC last I knew (Slayer Of Hideous Camaros)

 

Actually it's both. OHV just refers to the valves being above the head, as apposed to from the side, as in an old flat head motor. OHC, means the cams are also located above the heads. So you can be both. IN that context though, I'm sure it's a typo.

 

Is it both? I know that the mustang engine is SOHC, but i thought all overhead valvers were pushrod actuated, and i know the mustang does not have pushrods.

 

Technically, it is. However, the term "OHV" is generally used in regards to non-OHC engines.

 

OHV = OverHead valve
OHC = OverHead Cam
SOHC = Single OverHead Cam
DOHC = Double OverHead Cam

The real confusion is coming from the OHV term. Back in the old days (aka: mid 50's or so), the engines had the cam in the block pretty much where it is today, but the valves actually mounted in the BLOCK, not the head. The head was not much more than a flat plate with a chamber cut in it that connected the bore to the valves. Low compression. Crappy air flow. Very bad knocking (which lead to low compressions...). But cheap and easy to manufacture.

Than along came a better engine (and I want to scream because I can't remember which was the first American OHV engine!!! I want to say the 260 SBC) that placed the valves directly over the bore in the cylinder heads. This was refered to as an OverHead Valve engine (vs the standard "flat" engines of the time). Much better design all the way around, except, of course, for the extra expense of machining the heads. This was a very costly operation at the time. Before long, almost all of the American V type engines became "OHV" with a cam sitting down in the block just above the crankshaft. So THAT became the standard engine...

There was also another engine design out there, just not used much: Single OverHead Cam or even Dual OverHead Cam engines. These were all OHV engines in that the valves WHERE located right above the bores, but instead of using pushrods and rocker arms (which have a lot of mass and limit the high RPM usability of the engines...), they had the cam (or cams) sitting in the head directly above the valves. From there, there was a lot of different methods to operate the valves that were very light weight and allowed high RPM usage. One thing to keep in mind is that almost by definition, any SOHC or DOHC IS an OHV engine. That is probably why they don't refer to them as SOHCOHV and DOHCOHV engines...

One more point of confusion on the overhead cam engines: To start with, all the overhead cam AUTOMOBILE engines were inline 4 or inline 6 engines (and yes, I am SURE there is an exception or two to this rule. Doesn't matter for this discusion!). So, they either had a single cam operating the intake and exhaust (SOHC) or they had a cam for the intake and a cam for the exhaust (DOHC). What do you call an engine line the 05 24 valve engine that actually HAS dual overhead cams (one for each bank)? Most people stick to the standard of "SOHC" because it is still using a single came to operate both the intake and exhaust valves.

And just because I am on a roll, none of this is actually new! As an example: The P-51 and Spitfire aircraft were powered with a Roles Royce Merlin V-12 engine. This was a liquid cooled, 4 valve per cyclinder, SOHC engine that also was fuel injected and had a two stage supercharger on it. And that was 65 years ago....

So: The 05 24 valve engine IS OHV and it IS SOHC at the same time.

 

Thanks RRRoamer, i guess i already knew that (besides most of the history part), i just didnt really think about it technically or literally.