Robert N. Eaton spoke forth with the blessed manuscript:
> What I was thinking, and I apologize for not stating it, was that the
> valves should be redesigned proportionally in all dimensions such that
> the head area is 1/2 that of a single valve. This being the case, each
> redesigned valve would weigh/mass 1/4 as much as the larger valve. Valve
> springs would be proportionately lighter, both in mass and pressure.
> Thus the reciprocating mass of each valve, being on the order of 1/4
> that of the larger valve assembly, would allow a substantial increase in
> rpm without valve float.
No problem, I was just using actual production parts to illustrate my point.
> All in all, light multi valves allow higher rpm and greater volumetric
> efficiency than two large valves per cylinder, as the Miller,
> Meyer-Drake-Offenhausers did at Indianapolis. Even though the big Offy
> wasn't a high revver (long stroke, frightening piston speed,) its
> multi-valve pent-roof head lent high volumetric efficiency to a very
> tough, rugged engine, which made it supreme at the Brickyard for
> decades. The small Offies and Millers spun like hell and developed
> amazing power for their size.
I think it really depends on what you're going for, and what you're doing.
For all around driving you want more low end torque. Now I'm not saying that
this isn't possible with a 4V motor, but something like this has never really
shown up.
For racing, what you really want isn't peak numbers, but area under the HP
curve. That area is going to be strongly influenced by torque curves. I've
yet to see anyone compare the two. My feelng is a fairly high revving gen3/4
small block that was spinning to 8-9000rpm, would make a lot more torque under
the curve than most anything out there. The trouble with a gen3/4 chevy
motor, is that the PCM is only good to 8000rpm, to get beyond that you have to
switch to another computer to run the thing. Also, you can build a 7L (427ci)
motor that will rev to 8500rpm, while having fairly sane piston speeds.
Controlling the valve train isn't that hard, provided you're not asking the
engine to spin that fast for hours on end.
> It has been only in the past decade or so, that race proven developments
> for engines have filtered down to production cars. I only wish more of
> them were in American designed vehicles. I realize that NASCAR has
> developed pushrod technology to the limit, but I really wish they would
> let the Northstar engine race. Although it would take a couple of years
> to sort out, I really think it would show those good-ol-boys how.
I would argue otherwise, combustion chamber design has not been static for the
past 50 years, the racers have learned things there, and it has filtered down
quickly to the production cars.
Also, the nascar engine shops are anything but drunken good ol boy rednecks.
They don't operate the way the stereotype says they do. They are scientific
in their approach to finding power, and all extremely intelligent. The fellow
running Hendrick's motorshop used to build Penskes Champ car motors. Most of
those NASCAR engine builders are begging to run EFI.
Also, with some of the latest rules changes this season, they don't have to go
nuts building a valvetrain that lives, as NASCAR has been mandating which rear
gear to use, which effectively limits the rpm they can turn.
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