[Shotimes] (OT) Marauder

Thu, 7 Nov 2002 15:18:19 -0500

Not one cam lobe per valve. I indicated using a v-rocker to handle two
valves from one lobe. You're still left with four lobes per cylinder length,
which isn't a problem, until you remember that you've got to put bearings in
there as well.

As for KISS working in this application, I'm not entirely sold on that. Ford
claims that it's cheaper to produce DOHC heads than SOHC heads. I'm guessing
that cams are dirt-cheap for them, but these new-fangled ;) rockers aren't.

While you are looking at the slender rockers and bores in Honda's motor, be
sure to also look at the displacement and cost. Sure, any of this is
attainable, but there is a price to be paid. If Honda were to go to OHV,
(BTW) their valvetrain mass would increase, so we are back to the initial
problem of weight vs. cost.

Electrical valves do not make the point moot. They will probably show up
first in high-end cars and then stay there for a decade or two. It could be
a good thirty years before we see them, maybe longer since we already have
methods of changing lift, duration and timing via mechanical means.

David P

95MTX

~
----- Original Message -----
From: "Ron Nottingham" <nottingham@alltel.net>
To: <shotimes@autox.team.net>
Sent: Wednesday, November 06, 2002 08:30
Subject: Re: [Shotimes] (OT) Marauder

> The way you keep describing it (one cam lobe per valve), sure, it is
almost
> impossible to achieve.  You would go from 16 pushrods to 32, and from 16
> rocker arms to 32, it would get VERY crowded very fast.  And you are
right,
> David, it wouldn't be a good arrangement (I never said that way would
work).
>
> Obviously, you have never subscribed to the KISS philosophy, because the
> Y-rocker setup does work, has worked, and could work in the future.  It is
> easier and more simple to implement than having all those lobes and rods
and
> rockers.  Sure, the valves would need to be lighter to be able to utilize
> lighter load springs, but things are already going that way.  Smaller
bores,
> and using more slender rockers aren't a problem either, just look at some
of
> Honda's SOHC VTEC engines.  But also, as engines get smaller, they lose
> torque, and I thought that was main reason to keep larger engines?  Untill
> everyone is driving cars/trucks/suvs that are small enough, we will still
> have large engines.
>
> Still, the point is moot, as electrical valve opperation is the next
logical
> step...  Just as soon as a dual 14-volt/42-volt electrical system in cars
> becomes practical.  Which looks to be at least 10 years away.
>
> Ron N. - Dalton, GA
> 90 SHO
>
> ----- Original Message -----
> From: "David P" <jpotter8@bellsouth.net>
> To: <BJamesjr@aol.com>; <shotimes@autox.team.net>
> Sent: Wednesday, November 06, 2002 7:31 AM
> Subject: Re: [Shotimes] (OT) Marauder
>
>
> > Not three cams profiles per cylinder. Three profiles per cylinder
spacing.
> The
> > cylinders banks are offset from each other, so, looking at the total
> length
> > dedicated to one cylinder, you have to profile 1.5 cylinders (1 cylinder
> plus
> > 1/2 the cylinder from the opposite bank).
> >
> > I was wrong, though, as I was only thinking about the cylinders at the
end
> of
> > the block. This would only work on a V3! (or less) You actually will
have
> four
> > different profiles per cylinder spacing on a single-cam OHV setup
(intake
> and
> > exhaust of the cylinder that falls in the measured length, and the
intake
> of
> > one cylinder and exhaust of another cylinder on the opposite bank). You
> can
> > v-rocker the intake and exhaust to provide only four cams instead of
> eight.
> > Not a problem with large cylinder bore, but as motors get smaller, the
cam
> > lobe width has to decrease and the available length on the cam
decreases.
> A
> > decrease in the width of the cam lobe requires a reduction in the spring
> rate
> > of the valve, which requires a lightening of the valve, or durability of
> the
> > cam lobe becomes an issue. There a definite alternatives like titanium
and
> > beryllium alloys, but cost can rise considerably. I am thinking they
need
> to
> > find a way to coat carbon fibre with stainless  ; )
> >
> > The drawbacks of a little extra valvetrain mass is higher power
> consumption
> > and reduced rpm limit (unless money is no hindrance).
> >
> >
> > David P
> >
> > 95MTX
> >
> >
> >
> > ~
> > ----- Original Message -----
> > From: <BJamesjr@aol.com>
> > To: <shotimes@autox.team.net>
> > Sent: Monday, November 04, 2002 17:34
> > Subject: Re: [Shotimes] (OT) Marauder
> >
> >
> > > > A 4V OHV motor has to operate three separate cam
> > > > profiles per cylinder spacing vs SOHC operating only two.
> > > > The cam gets a bit more crowded.
> > >
> > > 3 cam profiles per cylinder?  On the surface you would think 2 valves-
2
> cam
> > lobes, 4 valves- 4 cam lobes.  However since OHV engines use rocker arms
I
> > would think a Y-shaped rocker arm could easily operate 2 valves with one
> > pushrod.  An enterprising person could have built a 4-valve head for a
V8
> > chevy long ago (may have even been done for all I know).  The only
> drawback
> > would be a little more valvetrain mass, but this would be counteracted
by
> 2
> > springs per cylinder instead of 1.
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