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Dakota Performance
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slow r/t man
Dodge Dakota
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10/18/2003
17:48:34
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 Subject: Hemi head flow #s
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I'm so tired of hearing how great the hemi is, What is so great about it? all that motor is is a set of cylinder heads. And just how good are they? I would love to see some flow #s. I'll bet a set of 2.02 R/T heads are just as good or better.
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gen1dak
Dodge Dakota
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10/19/2003
01:03:18
| RE: Hemi head flow #s
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Yes, Hemi is a head design. They just happen to be the best flowing design short of a jet engine. Look, Hemi's have popped up since the 20's, and they've always reset the standard. It's simple. Hemi heads offer the cleanest inlet and outlet for the mixture. Also, since the valves open on the centerline, there's no shrouding, just pure flow. Now, Magnums, and older LA's also open on centerline, which makes them better than other wedges, but when all is said and done, the Hemi is the King. Always has been, always will be. Why do you think they were legislated out of NHRA Pro Stock comp. waaaaaaaay back in the 70's? They were factored out because they simply made more power than anything else. Only in the past couple of years have they been allowed to re-enter the field of Pro Stock. Note, it's not the 426, but a new engine that'll take time to sort out. It's taken 25 years and millions of man-hours to get wedge heads even close. What other engine could be so competitive with the non-hemis right off the trailer. Given a little time, they'll probably be legislated out again. It's just taking a little time to sort out this new engine, and the wedges are a lot better than they once were. I don't have the flow numbers at hand. I'll have to get back to ya on that, but a well worked Magnum head would probably be close, maybe a touch better than a new production line hemi head. Do a little cleanup on that hemi head and it just walks away. That's just the way it is.
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EBL
Dodge Dakota
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10/19/2003
11:59:35
| RE: Hemi head flow #s
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I've read that a sphere is the ideal shape for a combustion chaimber. I believe that this has something to do with the area of a sphere is quite large compared to the surface area.
With a dished piston, a hemispherical head probably comes the closest to a true sphere than any other head design.
That said, I have also read that the hemi heads are not the most kind to emission standards. This could limit their longevity.
I don't think that this engine will have the life span of the 273/318/340/360 block.
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slow r/t man
Dodge Dakota
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10/19/2003
16:05:38
| RE: Hemi head flow #s
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Dodge sticks with their motors for a long time. Compared to chevy who seem to make a new one yearly. How many versions of the 350 have they made? I'm no chevy expert but gee LT1, LT4, LT6 LS1, I think thats just a few. Each one is a clean slate, not just different heads or something. Dodge makes a motor and keeps it for 40 years. I think this hemi motor will be around for a while. I just hope they put it in something light so it can show its potential
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gen1dak
Dodge Dakota
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10/19/2003
18:29:14
| RE: Hemi head flow #s
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The use of domes pistons with valve reliefs reduces the overall chamber volume, which improves emissions compliance. A central spark plug (or 2) improves combustion by cutting the burn distance in half. Quicker ignition leads to a more complete burn. The domed shape has a high resistance to detonation. I suspect Dodge plans on having this one around a while. Isn't there talk of a larger version in the works? Plus, just like the 273 of old, there's the 4.7 now. It has all the ingredients, and I suspect Dodge has the same plan in mind. The 4.7 will grow in displacement as needed (just like the LA series), especially if the more costly Hemi falls out of favor due to economics, emissions issues, or just internal politics.
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slow r/t man
Dodge Dakota
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10/19/2003
19:22:33
| RE: Hemi head flow #s
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the hemi is cheaper to produce than the 4.7 and less complicated, only 1 cam
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gen1dak
Dodge Dakota
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10/19/2003
21:51:04
| RE: Hemi head flow #s
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Actually, the new Hemi is less expensive than the 4.7 when production AND development costs are considered, mainly because the Hemi was developed with a proven formula. The cammer 4.7 was new for Mopar, hence the higher development costs. It is said that the Hemi is cheaper to produce than the 360. The 4.7 is cheaper than the 318. Since those engines were essentially identical, maybe the new Hemi isn't that much more costly to produce. All the better. If you happen to get a look at the valvetrain of a Hemi, you'll understand why it'd add to the cost. Pushrods, rockers...it adds up, and they aren't as easy to make (rockers) as the stamped Magnums.....But it is less complicated.
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