hemi advantage?
The old Hemi engines are better than the new ones. They had true "hemispherical" shaped combustion chambers. You could practically put a tennis ball in the head and run a flat blade across the head face and cut the ball in half.
The "new" Hemis are not true Hemis with round/spherical combustion chambers. They are more of a penta dome design. Better than a wedge, but not as good as a true Hemi.
The round/spherical combustion chamber allows for larger valves than the flat "wedge" design. Then angle the valves so the flow goes past the valve instead of around it, and you have better flow. In the wedge design, the mixture has to go around the valve. The geometry of the hemi allow for straighter ports and not having to go around the valve, but pass by it. It's simple fluid dynamics that any turns/bends in a port restrict flow. Maximum flow is in a straight line with no bends. The straighter you can keep your ports, the better they will flow.
Don Garlits once gave a speech at Mopar Nats on how he was trying to break 220 MPH. Chrysler had replaced the old 50's Hemis with the 413. He said that the big block could not make the power of the old Hemis. One track owner invited him to come race one weekend and offered him some money (like $1000) to race that weekend. He was running the 413 in the drag car, but couldn't get it near 220... 214, 216, ... No 220.
At the end of the day, he went to the control tower to get his earnings, and the owner was sitting behind his desk, with a gun on his desk, and an envelope and accused Don of "saving his motor for the Nats next weekend" and told him that he is only getting half of the money that they agreed on. Don states that you can't argue with a gun, so he took what was in the envelope and left.
The next weekend for the "Nats", he decided, "What the hell, lets put the old 392 Hemi back in the drag car."
So they put the Hemi in the car and took it to the track that next weekend. For kicks, he said that they decided to set the timing advance a little more and increase the boost on the blower trying to blow it up. Well, it didn't blow up. So they kept kicking up the advance and boost, and it wouldn't blow up, and he ended up breaking 220 MPH that weekend trying to blow up the Hemi. Don stated that the other track owner probably thought for sure that Don was "saving his motor for the Nats" after that, when he just couldn't get the big block to run as good as the old Hemi.
