Reading the other quench post prompted me to post a question that's always bugged me for a long time. I've learned through this forum that a short coming of the 426 Hemi's is that they are limited in N/A form when you start pushing HP to the limit, as compared to a more modern splayed valve engine (now I know that a HEMI can put down insane HP N/A, look at the Super Stock domination and so forth, I'm referring to Pro Stock and Pro Mod type engines so no haters please). I'm guessing the reason for this is that they have no quench in them and the insane piston weights that are needed to get compression. Why has no one "filled in" the sides of the chambers to cut down on the cc's and provide some quench, much like the Gen III hemis's, especially the 09 and later engines? Do Hemi's really need quench because of the centrally located spark plug? It seems that was the way that Mopar was going when they developed the Ball Stud Hemi in the early 70's (similar to a Boss 9 head, and we all know those things make serious steam)but I thought I would ask the engine builders and the Hemi guys on here because I'm just guessing.

This is what Dick Landy did w/ the piston to acheive (some of) what you're talking about:
http://www.hotrod.com/projectbuild/1970_dodge_super_bee_hemi_engine/photo_06.html

You'd think flame travel may be an issue with that Landy piston.

Plus it weighs a ton, and, you would never get as good or tight of quench as compared to a flat top and a filled in chamber. You have to give it to DLI for coming up with that to bandaid the problem. Those pistons are kind of along the same line as the KB pistons for RB's that have the big kick up on the dome for use with the 906 heads that are to take up the dead space in the open chamber.

i dont think quench is as important on a hemi. you atomaticly get some sort of quench because of the shape, the piston "grinds" the gases (if that makes any sence)wich i belive causes some turbulence. aldough i know that you can run more comp than the wedge on pump gas. I ran my 478 with 13.75 comp ratio on 93 okt but with 28* advance

That piston design never really took off,most hemi pistons are designed to conform to the head and as with any piston the closer to the head chamber the piston comes the better the efficiency of combustion on a cylinder design that is superior with the charge and exhaust inherient to the design.Ignition and flame propagation is centrally located and intake charge is directed to the compression zone as well as the the exhaust is directed to the exit valve location.There is little turbulance encountered in the charge and exhaust.Hemi,semi hemi,and canted valve heads will alway perform better than a straight line valve arrangment.Simply put a piston that conforms to the combustion chamber will alway be more efficient because it has a more uniform area of compression and ignition,a flat piston with a small combustion chamber and a straight line valve arrangment tends to load the piston unevenly,quench helps even the load.

The disadvantage the Hemi has is NOT from quench.......it's from terrible valve angles (for a naturally aspirated application) and piston weight...........and the ONLY reason Hemi's do well in Super Stock is because they have two carbs, instead of one like the Chevy's.....

The hemi valve angles are what makes them so great NA, that is not a down fall at all. If any NA down fall it it the heavy pistons required with high compression ratios. The ports may be a hair big for a NA 426 but throw a few more cubes in it and they are not too big at all. With a maximum effort port job and 550 or so cubes you can make close to 1000 hp with the stock castings so they are no slouch! Try that with a 906 or even a factory Max wedge casting.

BTW how small can you mill the hemi chambers down to any how?

What makes the valve angles terrible? What are the valve angles? By looking at a cut away it appears that they are pretty steep, but it also appears that the angle lends itself for a good short side in the intake ports, and due to having opposed valves, it doesn't appear that they would cause any shrouding.

The valve angle, piston weight, rod lenth, port volume and number of carbs contribute nothing in lack of peoformance ability as does the combustion chamber shape.

the down side of the Hemi in N/A use is directly related to the design of it's combustion chamber.
It cannot burn all of the area including that around the sides of the piston dome as quickly as a wedge chamber. The rate of burn is much slower regardless of the compression. There's no way it can burn all that area and make the same power as a B1 55cc chamber.
That is until you add some boost. Then it all turs around 180 degrees

Most of what everone has stated I agree with. The SS cars were just dead ringers.

Ford actually did what a lot of what is being referring to. Its called a Boss 429.

Another inherant problem with the chamber is a horrible surface to volume ratio. Lots of area for heat loss.

So what's it's advantage with forced induction? Do all of the advantages seriously outweigh the disadvantages when boost is added? In my original post I mentioned the Boss 429, why does no one make a HEMI head with a chamber like that (and like the Gen III Hemis)? Sure would cut down on piston weight and make a more efficient chamber.

Fred, or anyone else on here, do you have one of the current state of the art 426 hemi N/A pistons(baseball looking) that you are willing to take a pictureof and show what it takes to make power in theN/A Elephant motors, NHRA Stock, SS or old Pro Stock

with all very large bore and stroke HEMI'S I own
there's not much that translates from what an SS Hemi pistion is shaped like.By using a 4.5" bore and stroke 4.5" or 4 3/4". everything we spoke about changes considerably.
nor have anything I would consider trick in the SS world.

However I did pull these from a trash can when after INDY when a Barton motor came apart in an SS car. what strikes me here is the out of the box appearance and far from what I expeceted to see from one of their motors.Later I learned this was not one of their "A" combos and no likely to have the trick stuff.

2

I expected to see a piston much more shaped to follow the chamber shape and valve reliefs hand fitted . then again I haven't been inide a 426 size motor in some time

this is a D-5 sideby side with stock. look at differences ring pac location wristpin and dome shape