Hemispherical heads: 2T, 3T, 22R, 3M, Vseries

[Radar]

Basic run down -
- "With the hemispherical combustion chamber design, the intake and exhaust valves are usually on opposite sides of the chamber, unlike the in-line valve arrangement common to most engines with wedge-shaped combustion chambers." - Wiki
- "With a hemispherical chamber, larger valves are possible and a straighter, less restrictive flow path can be provided for the air/fuel mixture." - Wiki

Hemispherical combustion chamber:

In a HEMI engine, the surface area is much smaller than in a flat head, so less heat escapes and peak pressure can be higher.
It's known for reducing knocking with being more forgiving of octane levels.

I don't know enough about it all, but in a perfect world where we didn't have to worry about emissions, shouldn't these motors be able to go harder than other motors once forced induction is applied due to the thermal efficiency and flow?



Very cool side note, in 1940 Chrysler produced a inverted v16 that produced over 3000+hp
In the P-47 at 15,000 feet it pushed the aircraft at 504mph.. The important thing to keep in mind about this engine is that it was a Hemi headed, push rod valve activated type.

[Billzilla]

Well no, hemi chambers are crappy compared to a decent one that has squish areas. There's no reason why you'd want to use one over a good design if you have the choice.

[Norbie]

It's very difficult to get a decent compression ratio out of a hemi. You can use massively domed pistons but that causes other problems. Definitely not suitable for modern engines where the trend is for higher CR, even in turbocharged engines.

[MRMOPARMAN]

shouldn't these motors be able to go harder than other motors once forced induction is applied due to the thermal efficiency and flow?

in the old days before decent head design, hemi heads were the shit, especially when supercharging, look at drag racing history, a hemi or hemi derived engine absolutely killed american drag racing (cant remember the class, top fuel or pro stock maybe) every year except 1966, when a ford sohc won.

like bill and norbie said, head design has changed to the point where TRUE hemi heads are outdated, produce shitful emissions and are less powerful. this increases bigtime when naturally aspirated as norbie bout needing domed pistons to get decent comp out of them..

dont believe everything you read.. new chrysler Hemi's arent true hemi's.. even the old chrysler Hemi 6 wasnt a true Hemi.

hemi heads were originally developed for planes, and the idea had been around quite a few years before chrysler get their hands on the design.

[Hash_ra23]

isnt another reason that ur limited to two valves per cylinder?

[Radar]

So whats the best cyl head for power in the 2.0L category?

[MRMOPARMAN]

3sge beams, cosworth are pretty good, f20c honda head.. theres heaps of heads out there that are substansially better than ye olde 18rg/3tgte heads

[Radar]

I guess your all right, after all it is over 30yrs old =] How about a diesel 1.8L to 2.4L with a decent flowing head.. any of them?