What makes it a...

[Cuda_Shizzle007]

So after reading and seeing different things, I wanted to pose the question...Is a Hemi 426 basically a Max Wedge 426 with the Hemi heads? Am I wrong on this? I thought the Hemi was a hemi because of the plug placement, but I heard somewhere it was the heads that defined it as a Hemi? Can someone give me the true breakdown, I am confuzald.

[71bigblock]

The heads define a hemi, the valves are at an angle to create a swirling effect.   

[Cuda_Shizzle007]

I heard that the placement of the valves create a perfect combustion chamber directly above the spark plugs. Is this true? Also if the heads make a hemi, why do they cost so much (non original).

[Jacksboys]

The heads define a hemi, the valves are at an angle to create a swirling effect.   

Also the chamber looks like half of a sphere with a centered sparkplug, which would direct the explosive power towards the center of the piston.

If you combine the large valves, great air flow, centered sparkplug, and chamber design; you have a head that can provide lots of power if the rest of the engine is setup correctly.  The bad thing is that the Hemi engine weighed almost 100 pounds more than the 440.

[pink panther]

The Hemi is derived from " Hemispherical chambered head design"

[HP2]

Hemi is short for hemispherical, so it is the heads that define an engine as hemi. With a semi-round chamber, it only makes sense to have the plugs at the top. There are other hemis out there, they are not just a mopar thing. Most late model, dual cam imports use hemi heads on their engines. Heck, even the K cars in the 80s used hemi headed engines. They even went so far as to use left over hemi badges from the muscle era on them as well.

It's not the placement of the valves that define the chamber, but actually the opposite. The size of the chamber allows the valve placement to be directly opposite each other. While very efficient and effective for high rpm use, it may be too much of a good thing for anything but all out horsepower production. The round chamber displaces a considerable amount of volume and requires very large (that would mean heavy) piston domes to achieve high compresion. That is why the Hemi is so well suited to blown appplications like what you see in top Fuel and Funny Cars. The  pent roof, or semi-hemi design seem to be more effective at low to middle engine speeds as even modern mopar Pro Stock motors, as well as the current production Hemi, are not true hemispherical head designs.

Also don't forget that the era that these engines were developed in often had factory or sanctioning body rules that drove developement. The 426 max wedge was a very well developed engine program, the 440 didn't exist, so it was a natural to adapt the hemi head to the 426, plus it meet with nascar's cubic inch requirements, which was the reason for development to begin with. GM had a performance moritorium on their division with a 400 cid limit, which is why so many of thier early performance engines were under 400 inches. There were all sort sof variables that seem pretty distant and unbeleivable to us now.

[Cuda_Shizzle007]

So what drives up the cost? Is it the cost to make, name, or low volume (new crate engine wise). If its all about the heads, building one to me shouldn't be much more than a 440, so why the 13K price tag? 

[Jacksboys]

Is it the cost to make, name, or low volume (new crate engine wise).

It is a combination of all three.
1. The heads were not cheap to produce.
2. There were very few produced.
3. Now people want them, so the demand drives the prices up.

[Jacksboys]

Wow, all this and no one has tried to compare apples with apples, or in this case, oranges with tangerines. Suppose we compare a 426 Big block and a small block that has been stroked to 426 inches. Now make your comparisons. A stroked small block is a heck of an engine. You have the cubes and you lose the weight. This also is beneficial when it comes to handling and turning. The car is balanced better instead of being front end heavy. So I now reask the original question. Assuming the cubes were the same in the two, which is better, a small block or a big block?  

Depends on what you plan on building the car for:  drag racing or autocross?

[Cuda_Shizzle007]

So engine wise which block(s) can you purchase and add the Hemi heads to? I would'nt have a problem getting a small block and punching it out to 426. I going air suspension, possibly hemi power, and original muscle car look inside and out (except the rims).

A secondary question: Are they no longer building the blocks and heads to make a hemi, or are the ones produced not the same as the one made back in the late 60's to early 70's?

[Chryco Psycho]

the Hemi block is totally unique , no other block will accept the Hemi heads , it does share most of the design features of the Wedge blocks there are oil drain passages & head bolt bosses that do not exist on wedge blocks
 there are for now anyway new blocks available from Mopar & there are a few other companies that produce Hemi blocks as well , heads are even more available from various sources
 as an option Stage V engineering does make a Hemi head that will bolt to the wedge block with some clearancing to the block for pushrods & using external oil drain lines

[HP2]

If your going to build a Hemi, the easiest way to do it is just buy a new Hemi block and bolt on the new Hemi heads.

Like CP stated, Stage V does make a conversion Hemi head that can be bolted on to 383 low deck and/or 440 high deck blocks. It does require cutting and welding the block for push rod clearence as well as adding external oil return lines. Because of the layout, it reuqires a special intake and valve gear that does not interhange with the 426 version, but you still get the big, wide valve covers with spark plugs in the middle of them. Also, in as cast form, Stage V heads actually flow better than the original 426 style head. Going with a Stage V conversion Hemi you might be able to save 2-3 grand over buying a crate, or building a Hemi from off the shelf parts, but your fabrication ability must be significantly higher to do so.

The new 426 Hemi heads and blocks are similar to, but not exactly identical to the one produced from 64-72, but all of the parts are interchangable between the two.

Small blocks cannot use 426 heads regardless of the displacement. As an aside, the new siamese bore small block can be bored and stroked to 440 inches, but it is still a small block and uses dedicated small block parts. If you want a Hemi head on a small block, you have to use an R3 iron or P5 aluminum block. You then have to use the mopar P5 cylinder head, which isn't a true Hemi but a pent roof design like the 5.7 street Hemis of today. If you can find the parts to build this, expect it to run about twice what a crate 426 Hemi would run as these were produced in even smaller quantities and were only used by the NHRA Pro Stock Truck racers in the late 90s. However, they make big power and would defiently be a street freak and draw a lot of attention.

[matt63]

The major reasons that the hemis are more expensive due to the head design, elaborate valve train and the domed pistons.  The relatively small production quantities probably don't help either.  As a note, I heard that they have built more aftermarket crate hemis than they did production hemis from '66 to '71!

[Cuda_Shizzle007]

So is the 392 hemi a true hemi design?

I am not dead set on a hemi in paticular, but I went to look at a Cuda for sale and the guy had a Hemi Belvedere that he fired up after I told him I had never heard a Hemi. The sound that roared was noting I had ever heard, and I knew I wanted one, or something that sounded the same. But based on head and piston design, I think the only way to get that sound is by getting hemi. 
 

[HP2]

Which 392? The 1958 version is a true hemi head. The 2008 version is a pent roof, quench pad design, but is still more of a Hemi than a 440 or 383.

A lot of that roar is from compression. Most hemis were built for serious power, so they have a serious bark to them.