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As stated, what exactly is "the head" of the engine.. is it the valve cover, and all the goodies beneath? or just the goodies.. my searches havent provided me with the info i need..
 

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Your electrical friend
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The head is the head of the combustion chamber. Where the valves are, and lots of times the cam(s). Anything above the block on an engine is the head, with the exception of things that bolt to the head like the intake manifold and exhaust manifolds or headers. See that's where us 4 banger guys get confused and refer to our "intake" when really it's intake piping, your actual intake is your intake manifold, what your throttle body sets on top of. V6 and V8 guys don't refer to intake like we do, when they say intake they mean their intake manifold, not some madrel bent tubing that goes from their filter to their TB. Anyway, you're right, everything between the VC and the block is the head, it's a seperate unit from the block. Now, some V6's and V8's don't have their cams in their heads, hence they aren't referred to as having overhead cams, their cams aren't over the top of the head. They have a single cam down in the block that drives pushrods up through the block into the heads to operate the valves. No easy cam swap for these guys. If it were up to me, everything would be 4 valves per cylinder, dual overhead cams per head, regardless what it is. I'm sure you know a lot of this, but I didn't assume anything, so I didn't intend to be condescending or anything.
 

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MFCoEJ Juror
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toolapcfan said:
The head is the head of the combustion chamber. Where the valves are, and lots of times the cam(s). Anything above the block on an engine is the head, with the exception of things that bolt to the head like the intake manifold and exhaust manifolds or headers. See that's where us 4 banger guys get confused and refer to our "intake" when really it's intake piping, your actual intake is your intake manifold, what your throttle body sets on top of. V6 and V8 guys don't refer to intake like we do, when they say intake they mean their intake manifold, not some madrel bent tubing that goes from their filter to their TB. Anyway, you're right, everything between the VC and the block is the head, it's a seperate unit from the block. Now, some V6's and V8's don't have their cams in their heads, hence they aren't referred to as having overhead cams, their cams aren't over the top of the head. They have a single cam down in the block that drives pushrods up through the block into the heads to operate the valves. No easy cam swap for these guys. If it were up to me, everything would be 4 valves per cylinder, dual overhead cams per head, regardless what it is. I'm sure you know a lot of this, but I didn't assume anything, so I didn't intend to be condescending or anything.
You know whats funny, just this weekend I learned what a Hemi actually is. I know import engines, kindof, and I was discussing it with my dad who of course knows nothing about 4bangers and know Detroit muscle. Anyway, he was describing what a Hemi is, and I am like "All 16 valve engines are Hemi then."
And he didnt believe me so when and looked up some pictures and he said, yeah thatd be a Hemi.

So this is one reason why our import engines are so much more durable than the average American engine.

FYI: Hemi is a fully domed combustion head chamber with the spark plug in the top dead center. When the spark forces the combustion straight down onto the piston, less wear occurs. As opposed to the "Wedge" style that most 8 valve heads have.
 

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Interesting

Anyway, he was describing what a Hemi is, and I am like "All 16 valve engines are Hemi then."
And he didnt believe me so when and looked up some pictures and he said, yeah thatd be a Hemi.

FYI: Hemi is a fully domed combustion head chamber with the spark plug in the top dead center. When the spark forces the combustion straight down onto the piston, less wear occurs. As opposed to the "Wedge" style that most 8 valve heads have.
I was under the impression (looking for corrections here) that "hemi" is short for hemispherical (Sphere cut with a plane parellel to equitorial plane). So the question is, does "domed" = hemispherical? If not, is the GA truely hemispherical?

Using a cut of a sphere makes a lot of sence in terms of pure physics in a perfect engine. (Reality may vary!)
 

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MFCoEJ Juror
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Re: Interesting

Foof said:
I was under the impression (looking for corrections here) that "hemi" is short for hemispherical (Sphere cut with a plane parellel to equitorial plane). So the question is, does "domed" = hemispherical? If not, is the GA truely hemispherical?

Using a cut of a sphere makes a lot of sence in terms of pure physics in a perfect engine. (Reality may vary!)
Well, if you compare the GA to a Wedge head and a Hemi head, the GA is much closer to the Hemi.

Now are you talking diameterwise?? If it was a true hemisphere its depth would equal 1/2 its diameter. Is the label Hemi, based on its mathmatical size or its general shape. If it is shape, then yes, the GA is a hemi...but if it is based on exact mathmatical proportions then no, its not deep enough.

Someone will have to clarify this.
 

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if you look at a dome (side view) it is a hemisphere. right? im sure thats where they got the name...
 

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Cone Dodger
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later v8's also have dohc, and no pushrods, and even the v6's, pushrods are of the olden times, just unwanted excessive drivetrain weight, and more components to break, wherein dohc engines, have tappets hydraulic or not........and more durable for higher rpm's.....
 

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I don't believe that ALL 16 valve DOHC engines are hemi-heads. Just because the spark plug goes straight down the center doesn't make it a hemi-head. Many engines use heads which are flat at the very top of the chamber where the plug comes in, then the sides of the chamber where the valves are are slanted, kind of like and upside-down V with the top flattened. This is easier to manufacture than a true hemi-head.
 
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