Bob Holtzman wrote:
> On Tue, 22 Nov 2005, Mike Garfias wrote:
>
>
>> Robert N. Eaton spoke forth with the blessed manuscript:
>>
>>> Mike Garfias wrote:
>>>
>>>
>>>> Two small valves weigh more than one single one.
>>>>
>>> Not really. Think cube-square law.
>>>
>> Yes, really. you're failing to take into account the weight of the stem.
>>
>> Two valves = two stems
>>
>
> How about thinking weight per flow area? You will still be rev limited but
> should make more power at the revs available because you're moving more
> mixture.
>
>
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.
One caveat. The small valves might have to open wider in so as to allow
increased flow (just how much I don't know.) In this case, the valve
stem might have to be a little longer, adding mass. However, the
lighter valve springs would allow greater valve motion before
compressing coil to coil.
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.
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.
Now I'll shut up. Sorry for the long OT.
Bob Eaton
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