[Shotimes] (OT) Marauder
Ron Nottingham
nottingham@alltel.net
Mon, 4 Nov 2002 18:54:47 -0500
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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