[Shotimes] (OT) Marauder

Wed, 6 Nov 2002 08:26:50 -0500

The airflow characteristics of 4V heads will always be better than 2V. Why
would we have 2V if this fact were not true? Mfg's seek profit reduction?

No, motors are not 100% efficient at burning fuel. The engine is burning the
same percentage of fuel at it's torque peak as it is most any other rpm.
What changes is the motor's ability to draw in air and the percentage of
time spent on the burn cycle (stroke time vs. burn rate).

Quit quoting me cars that are on the market. A mfg's design capabilities and
compromise decisions have no bearing on physics.

Try this:

Draw a circle. Draw two circles within this circle, as large as possible
without passing through each other or the larger circle. Calculate their
surface area. Now, take the remaining area between these two circles and the
outer circle and draw in two circles there under the same rules. Add their
surface area to the original surface area. Did the total surface area
increase? Now, obviously head design is not as simple as this, but it does
figure that you can get more airflow and more even airflow into a head with
more valves. I don't care who currently can't or doesn't do it.

David P

95MTX

~
----- Original Message -----
From: "Ron Nottingham" <nottingham@alltel.net>
To: "David P" <jpotter8@bellsouth.net>; <shotimes@autox.team.net>
Sent: Monday, November 04, 2002 18:54
Subject: Re: [Shotimes] (OT) Marauder

> How could the cam get more crowded?  You act like a 4-valve head has never
> been made for a cam-in-block engine, and that it is impossible.  It has
been
> done before, many, many times.  All that is used is a normal V8 camshaft
> with 16 lobes for the intake and exhaust valves.  Two valves are operated
> via one pushrod, and a Y-shaped rocker arm.  Go pick up some back issues
of
> Hot Rod or Car Craft, they usually have something in one of them at least
> once a year for the past 20+ years.
>
> Now, since when did physics change?  Engines have always been most
efficient
> at their torque peaks.  Have you ever seen a CVT (Continuously Variable
> Transmission) in action?  Where does it spend most of it's time?  At the
> horsepower peak?  Uh, no, they spend most of their time around the torque
> peak.  Why?  Because an engine is most efficient there.  Now, to get this
> effeciency, would you think the engine is not burning all the fuel it can?
> If you go higher, it is burning less of the fuel that is in the air/fuel
> mixture.
>
> The Honda Civic Si is EPA rated at 26mpg city, and 30mpg hwy.   The
Covette
> Z06, with more than twice the torque and horsepower, gets 19mpg city and
> 28mpg hwy.  The new Mustang Mach 1 (complete with 4-valve DOHC engine)
gets
> 17mpg city and 25mpg hwy.  What does all this prove?  Absolutely nothing
:-)
> BTW, a Corvette with a 4-spd auto still gets 18mpg city, and 26mpg hwy.
And
> oh my(!) the Honda S2000 gets only 20mpg city, and 26mpg hwy(!)
>
> Oh well, the OHV engine is living on life support (never said it wasn't),
> but to discount that 4-valve OHC engines are always better is not totally
> true.
>
> Ron N. - Dalton, GA
> 90 SHO
>
> ----- Original Message -----
> From: "David P" <jpotter8@bellsouth.net>
>
>
> > Actually, Ron, it is a slight bit different since a SOHC motor gets TWO
> cams
> > (in any V configuration) while a 4V OHV would ostensibly have only one
cam
> > to operate both heads. 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. Sure, they could put two cams into the block, but why
would
> > they want to double the drawback of an OHV motor, they valvetrain
weight?
> In
> > case no one has noticed, we are moving away from low-torque passenger
car
> > motors (engines, gerbils, whatever) to those that place the torque at
the
> > high end of the scale. Gobs of low-end torque means higher emissions of
> bad
> > fumes. To get gobs of air into the cylinder at lower speeds you have to
> > restrict airflow turbulence. Turbulence, however, promotes air/fuel
> mixing.
> > It's a compromise that takes a lot of time and money to perfect. Look at
> the
> > work that was required to develop the LS1 intake. If the Corvette had
not
> > been such a solid seller, and they had not been able to share so much of
> the
> > motor with other high-volume vehicles, they would never have been given
> half
> > the time and money they were to develop the intake system.  Such as it
is,
> > they were, and the LS1 and subsequent LS6 are very good OHV motors,
> however,
> > they are still near the bottom of ENGINE evolutionary development, just
> > above steam-driven pistons. OHC may be costlier, but it has less
> drivetrain
> > mass, which will allows for higher revolutions, which allows for more
> > efficient engines. SOHC and DOHC are replacing OHV designs as we talk
> about
> > it, so it's not really an issue of will this occur, as much as a
question
> of
> > when will you no longer be able to find an OHV motor in a passenger car.
> > You've got to meet EPA guidelines if you want to avoid being fined out
of
> > existence. What is Chevy going to do with the Corvette when the stakes
are
> > raised to 50mpg? Put in 2.53 gears? What about 75mpg? 100?
> >
> >
> >
> >
> > David P
> >
> > 95MTX
> >
> >
> >
> > ~
> > ----- Original Message -----
> > From: "Ron Nottingham" <nottingham@alltel.net>
> > To: <shotimes@autox.team.net>
> > Sent: Monday, November 04, 2002 09:22
> > Subject: Re: [Shotimes] (OT) Marauder
> >
> >
> > > I, for one, would like to see "plenty of 4-valve OHV" engines (the
> correct
> > > term, since a motor is electric :-).  I do not know of any production
> > > pushrod 4-valvers.  Although I have seen many different designs for
> them.
> > > No different than, say, a SOHC 4-valve engine, and there are plenty of
> > those
> > > around, as Honda is a HUGE manufacturer of SOHC 4-valve auto engines.
> > Most
> > > Civics and Accords only came with 1 cam :-)
> > >
> > > Ron N. - Dalton, GA
> > > 90 SHO
> > >
> > > ----- Original Message -----
> > > From: "Midwest SHO Specialists SHOtimes"
> > <MidwestSHOspecialists@hotmail.com>
> > >
> > >
> > > >      Actually there are plenty of of 4 valve OHV motors around.  You
> do
> > > not
> > > > need to squeeze extra lobes on the cam either.  All of the pushrod
OHV
> 4
> > > > valve engines that I have seen have fingers in the heads that
operate
> > both
> > > > intake valves off of one pushrod.  This is very similar to how SOHC
> 16V
> > 4
> > > > bangers operate.
> > > >
> > > >      Also Yamaha didn't have the advances that we have now when they
> > were
> > > > designing this motor.  Keep in mind that the motor was designed 17
> years
> > > > ago!  That's amazing when you think about it.  They were waaaaay
ahead
> > of
> > > > their time.  I digress though.  Hydraulic tappets were not used for
> fear
> > > of
> > > > high RPM oil foaming which would have caused them to collapse.
> > > >
> > > > ~ Mike
> > > > ----- Original Message -----
> > > > From: "David P" <jpotter8@bellsouth.net>
> > > >
> > > > > Since all OHV motors are two-valvers, and four valves allow more
> > > efficient
> > > > > combustions, then pushrods DO have a bit to do with emissions, at
> > least
> > > > > until they figure out a way to cram 4V onto a single cam. Sure,
> > injector
> > > > > placement, intake flow, etc play a large part, but when
considering
> > > solely
> > > > > 2V vs. 4V, 4V is going to win on emissions and power. You think
> maybe
> > > > there
> > > > > is another reason why the Corvette runs a 2.73 final?
> > > > >
> > > > > As for OHC being high maintenance, I think you are forgetting that
> the
> > > SHO
> > > > > does not have a hydraulic tappet. Remove the hydraulic tappet from
> any
> > > OHV
> > > > > motor and it becomes just as maintenance intense. Not as expensive
> to
> > > > build,
> > > > > but just as expensive to maintain. If Yamaha had inserted
hydraulic
> > > > tappets
> > > > > into their design, we would not be sitting here exclaiming the
need
> to
> > > do
> > > > > the 60k on time.
> > > > >
> > > > > Sure, the small block (or more specifically, the OHV design) will
be
> > > > around
> > > > > for some time, but eventually it will be dropped in lieu of more
> > > efficient
> > > > > designs in our nation's quest for emissions reduction. Don't get
> upset
> > > > about
> > > > > it though, as OHC's days are numbered as well. There are much
better
> > > > > air/fuel injections systems on the boards and in testing that
don't
> > have
> > > > > valves as we conceive them that will see fruition in the last half
> of
> > > this
> > > > > century, leaving OHV as the predominant valve design of the 19th,
> 20th
> > > and
> > > > > 21st centuries. Not too bad a run, but definitely a technology
that
> > has
> > > > > outlived it's usefulness.
> > > > >
> > > > > ----- Original Message -----
> > > > > From: "Donald Mallinson" <dmall@mwonline.net>
> > > > >
> > > > > > Yes production was low, although that is what you said, not
> > > > > > i.  They also sold every one they made, and even ramped up
> > > > > > production and held it longer than planned to try to meet
> > > > > > demand.  You expected maybe they would sell them in Focus of
> > > > > > Camry numbers?  NO special vehicle sells in big numbers,
> > > > > > Cobra, RX7 etc.  But they did sell a lot of the basic
> > > > > > Caprice, a great tow vehicle and very good police car that
> > > > > > the police across the nation still lament not being able to
> > > > > > get.  They have never warmed up to the low torque and low HP
> > > > > > "High tech" Crown Vic.
> > > > > >
> > > > > > High emissions?  Not really, the small block chevy lives on
> > > > > > in the Vette and a huge amount of other applications as a
> > > > > > low emissions vehicle!   And don't spout the "low tech"
> > > > > > pushrod cam mantra.  The motor works and puts out more HP
> > > > > > and torque than competing motors from Ford.  Pushrods have
> > > > > > nothing to do with emissions, it is ignition and fuel
> > > > > > control more than anything, and combustion chamber design.
> > > > > > The new small blocks are as good as anything out there,
> > > > > > better than most.
> > > > > >
> > > > > > I am a basic fan of Ford, but there is NO, repeat, NO
> > > > > > arguing with the extreme success of the small block Chevy.
> > > > > > Ford had a similar motor, but they dumped it.  Now they are
> > > > > > really struggling with the more expensive to make and
> > > > > > maintain OHC motors.
> > > > > >
> > > > > > And yes, mods are plentiful, they work, and are cheap.  That
> > > > > > , my friend is the outline and model for the most successful
> > > > > > motor of all time, including today.  I am willing to bet the
> > > > > > small block is around longer than the OHC Ford motor.
> > > > > >
> > > > > > > ----- Original Message -----
> > > > > > > From: "Donald Mallinson" <dmall@mwonline.net>
> > > > > > >
> > > > > > >>I agree with much of what you say, but you imply that the
> > > > > > >>Impala from the mid 90's was not successful.  Nothing could
> > > > > > >>be farther from the truth.  That car sold above sticker for
> > > > > > >>its entire run, and was only killed when GM needed the plant
> > > > > > >>to build more prolific and profitable trucks/suv's.
> > > > > > >>
> > > > > > >>
> > > > > > > Well, I was looking at production nos. awhile ago, and they
were
> > > low.
> > > > > So
> > > > > > > what you are saying is that GM kept production low?  That
would
> > > > explain
> > > > > low
> > > > > > > sales and remaining residual demand.  Of course the mods will
be
> > > > > plentiful
> > > > > > > for that engine, but its old tech, high emissions design dooms
> it.
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