05-12-2003, 06:53 AM
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CC Member
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Join Date: Feb 2003
Location: Jacksonville Florida,
Posts: 82
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Not Ranked
I asked about the rod length. I looked it up and the 390, 427 and 428 all share the same rod length. Some may ask, so what? What this does is give the 427 a longer rod to stroke ratio. I'm no combustion engineer, but I have read that you need to park the piston at TDC for a relatively longer period of time so that the cylinder pressure has more time to fully develop at high rpm. It takes time for the flame front to develop. I'm pretty sure that all the competitive racers are using "long rod" engines these days to get that extra edge. The 427 has a slight edge in this way by design. Of course, that does mean you sacrifice some low end torque, where the longer stroke and lower rod to stroke ratio of the 428 will shine. Like most things, it is a balance. If you park the piston at TDC too long, then the pressure peak starts to fall off before the crank has rotated past TDC far enough to allow the leverage of the crank throw to work. That is why the long rod engine won't do as well at low rpm.
Charlie
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