The latest Steve Morris video was a good one which brought up the discussion of why a N/A wedge of equal CI would make more low to mid torque than an N/A gen 2 Hemi. Reading the comments was a bit interesting as some were calling the gen 2 Hemi chamber a crappy chamber. I have always been under the impression the Hemi chamber was superior to a wedge chamber. Some said the Hemi needs tons of timing to make peak power, like 40*, because they claim there is no quench pad like a wedge. In my mind, i thought the shape of the Hemi piston dome created a quench the whole circumference of the base of the dome, pushing the mixture to be burned to the central located spark plug above, hence, the perfect chamber. I have seen a few dyno vids where a 572 n/a hemi made peak power at 33* total.
I think the bigger part of the wedge being faster than a hemi n/a is more do to losing to much mixture out the exhaust valve due to valve arrangement at overlap. Blown is a whole different story, it cant leak fast enough to lose power. How does compression hurt power in a n/a hemi? I dont get it. What do you guys think?
https://youtu.be/RyQGlH2DGOU?si=bJEV-6nr6-LYsGtu

One commenter:

Monte definitely mentioned that a few times here- the hemi chamber is awesome for power adders and not great n/a. It’s the same reason why wedge chambers get softened on boosted applications too.

The gen 2 chambers were moved from dead center to canted to one side for convenience on installing those motors in the early B body on the assembly lines
The first gens, all three brands, were not

Wow, thats weird. The other thing on my mind besides finding best total timing is compression. From what i'm reading, n/a gen2 hemi's dont like too much compression. What would be too much compression on an n/a gen2 hemi? Current plan is 12:1 using a .040" gasket . .051 would give me 11.7:1. What should my target be for best compression to hit max power n/a on this combo?

Pro Stock Hemi engine builder When was the last time a Hei was run in prostock 50 years ago. Good thing about the internet everyone gets the chance to speak. More of an issue getting the compression in a Hemi chamber for a max effort NA deal.

It all seems like pretty normal YouTube comments.

He must be old. So, with my combo, do you see any issue with 12:1? I'm yet to clay it for quench and clearances measures.

Just looking at the piston spec page and its looks like FHO ordered these fit to my Custom heads, so should be ok.

Despite the torque difference between a wedge and Hemi, my dad’s 572 Hemi seems to make some good torque. I had two 1.24 60’s last time out. Thats at 3495lbs, footbrake, N/A. I think you’ll be happy with your new combo Dave.

That would definitely put a grin on my face. With Aluminum block, should put me back in my small block weight range at 3300 with me.

I've always been told the opposite about hemi ignition timing...that they don't like a lot of timing. Mine likes 34° naturally aspirated.
All my wedges have liked around 38°.

For a true hemispherical chamber you need a huge dome and that results in a ton of surface area that takes heat out of the chamber plus the actual fire stays something like 2mm from any surface so there is a ton of area that never burns completly and the piston is much heavier. The description of the chamber shaped like half a grapefruit peel is correct, even if the chamber in the head was a perfect hemisphere the actual combustion chamber would not be a hemisphere unless the piston was a flat top and even with a 650CID gen II you would still get something like 8 to 1 compression with a flat top. If your willing to accept a simple crossflow head as a hemi then the hemi can be great NA. The gen III is a good example of this, you can easily build a 440 with flat top pistons and end up with 13 to 1. In an aftermarket block you can go to about 470 CID and around 14 to 1 with a flat top... and just a 10 CC dome (much more in line with modern top of the line wedge style pistons) can get you well over 15 to one.

I'm still not convinced there is a huge TQ difference between the two if the CID is the same, the debate is always the 426 hemi VS the 440 6 pack and everyone completely ignores the 14 CID the hemi was lacking and the much longer duration cam, I would love to see someone build a 426 wedge with a hemi cam and see how much more TQ it had down low VS a 440 wedge... nobody would claim the wedge was still a TQ engine, it would lose a ton of low end TQ and would not have the top end sto match the hemi, in fact it would make less HP as the intake valve would be more shrouded than it is in the 440, you get significantly less tq and hp. If that was the comparison there would be no comparison in TQ or HP.

Agreed, mine make the most power at 33 degree n/a.

I agree. Sounds very logical to me.

Engine Masters did a comparison that is about as close as you will find.
The 440+6 put the whammy on the hemi so bad it's impossible to blame the 14 cubic inches. It was way more than anyone could justify for 4% more displacement.

Once the RPM was up the hemi ran away.

The runners and resulting velocity is a big factor. You get better chamber filling at peak torque than peak hp in most NA engines. The wedge chamber draws it so much easier without a big lumpy piston getting in the way.

Hemi Chambers are great for artificially packing under boost, but Obviously with a huge surface area (you are basically looking at 2 cereal bowls) which squeezes all the pressure toward the rings.

Hemi's are pretty horrible under vacuum or part throttle.

That enginemasters comparison was a joke. Worthless. They used the same exact cam grind in both to try and equalize. A Hemi doesn't like a wedge cam grind due to scavenging the intake charge out the exhaust on overlap. And the Hemi was low compression. Hemis become dogs below 10.5 to 1. And it was RPM limited. Hemis love to rev. Both engines should have had their combination optimized based on the needs of the engine design.


Hemis love compression. Gas Hemis usually run best on 30-33 degrees. The hemispherical chamber has the lowest surface to volume ratio of any shape. The shape allows for bigger valves in any given bore size, and the valve layout provides for a port with a straight shot at the valve. People love to hate on Hemis. With 75 years of technology advancement since Chrysler introduced the Hemi, yes there is now better designs both OEM and aftermarket. But there was NO production engine in the 60's factory equipped with a more capable head IMO.

Hemi secret: over-scavenging of the intake charge can be greatly reduced with a little bit of re-shaping with a grinder.