Re: 2 liter engine
The head on a 2 litre is so efficient to begin with that spending a lot of
money porting and polishing does not give you a big return. In fact
polishing really doesn't do much of anything for any head. Removing burrs,
cast lines, sharp edges in the combustion chamber is all that really needs
to be done to the 2 litre head.
Now... strapping on a set of Solex's and a "B" cam gives you up to 30
horsepower immediately in a 2 litre and you can do it in about 2 hours or
less. Or just add the "B" cam to your SU engine. The "B" cam is still
available from Nismo for $245. In fact, Isky still makes a cam that can be
bought for $145 but may be a bit radical for daily driving. Add to your SU's
and realize a significant boost in power. Porting and polishing won't do
that, especially in that amount of time.
Bob Davis
67.5 2L
Vintage Racer
----- Original Message -----
From: "Vicki Burrows" <gregnvicki@earthlink.net>
To: "datsunmike" <datsunmike@nyc.rr.com>
Cc: "milton3" <milton3@pobox.com>; "Peter Long" <Peter.Long@ecologic.ca>;
"roadster list" <datsun-roadsters@autox.team.net>
Sent: Wednesday, August 14, 2002 12:49 AM
Subject: Re: horsepower vs. torque
> I see what you are saying, and agree! Given the choice of bolting on a
Solex
> set up vs doing some quality port and cam work, I would take the port work
(as
> long as the machinest really knew what he/she was doing).
> Greg
>
> datsunmike wrote:
>
> > I still believe that $1500 spent on porting, a cam, a valve job and
better
> > valves would be as efficient if not more so. I think a Solex setup is at
> > least that in cost if not more.
> >
> > Mike
> >
> > ----- Original Message -----
> > From: "Vicki Burrows" <gregnvicki@earthlink.net>
> > To: "datsunmike" <datsunmike@nyc.rr.com>
> > Cc: "milton3" <milton3@pobox.com>; "Peter Long"
<Peter.Long@ecologic.ca>;
> > "roadster list" <datsun-roadsters@autox.team.net>
> > Sent: Tuesday, August 13, 2002 7:03 PM
> > Subject: Re: horsepower vs. torque
> >
> > > Well, since we are voicing opinions here, I am in the Mikuni/Weber
style
> > camp.
> > > You're right that the airflow is the key, but the manifold and carbs
for a
> > > Mikuni/Weber set up appear far more flow efficient. No offense to the
SU
> > cars,
> > > as SU's are excellent carburetors. However, the Mikuni/Weber set ups
are
> > far
> > > more tunable and offer many features that an SU simply cannot.
> > > Greg Burrows (soon with SK's)
> > >
> > > datsunmike wrote:
> > >
> > > > At more than $100 per HP gained it's awfully expensive.
> > > >
> > > > I bet getting a head properly ported and better valves (Manley) a
good 3
> > > > angle valve job and a different cam would enable a SU car to out
pull a
> > > > Solex car providing you get different needles especially for the
higher
> > RPMs
> > > > where I think the 1600s and 2000s run outta gas. A longer duration
cam
> > would
> > > > help that too.
> > > >
> > > > BTW, a 240 racer at Lime Rock for the SCCA Volvo Vintage races told
me
> > the
> > > > Mikuni factory was destroyed by fire and the carbs are NLA.
> > > >
> > > > Mike
> > > >
> > > > ----- Original Message -----
> > > > From: "milton3" <milton3@pobox.com>
> > > > To: "Peter Long" <Peter.Long@ecologic.ca>; "roadster list"
> > > > <datsun-roadsters@autox.team.net>
> > > > Sent: Monday, August 12, 2002 6:27 PM
> > > > Subject: Re: horsepower vs. torque
> > > >
> > > > > Hey Peter,
> > > > >
> > > > > I'm not picking on you for your comments, but voicing a different
> > opinion
> > > > > and explanation. There are benefits to both, and I wanna talk
about
> > where
> > > > > the power is located. I'm going to tie it in to the SU (.5*46mm)
v.
> > Solex
> > > > > (44mm) discussion from last week since that one didn't sit well
enough
> > to
> > > > > digest.
> > > > >
> > > > > Note: I'm only voicing my own opinions and trying to help folks
> > > > > understand the difference so they too can voice an opinion.
> > > > >
> > > > > On 12 Aug 2002, at 14:51, Peter Long wrote:
> > > > >
> > > > > > The rate of acceleration is greater. These are two extreme
> > > > > > examples to show you that 240 hp is not equal to 240 hp.... peak
> > > > > > horsepower ratings sell magazines, torque wins races."
> > > > >
> > > > > Funny thing though: The BMW Z cars only get to look at S2000 tail
> > lights.
> > > > > I've been on track in lapping sessions with both. The S2000s are
> > faster
> > > > > around Texas World Speedway's 2.8 mile road course. I've watched
them
> > > > > compete at AutoX's too, and the S2000s take the nod there too.
> > > > >
> > > > > Why? Because acceleration from a standstill isn't the only factor
> > when
> > > > > winning races. I'm going to suggest that you look at the HP v.
RPM
> > curve
> > > > > and compare the total area under the curve - matched to the right
> > driver
> > > > > the car with the greater total area takes the nod if it is geared
> > > > > perfectly for the event.
> > > > >
> > > > > But, the average driver (like me) needs the power (yes power, not
> > torque)
> > > > > at the RPM they are accelerating from. It is easier for a driver
like
> > me
> > > > > to deal with the power at the top of the RPM range because this
fits
> > with
> > > > > the idea of press the pedal harder to go faster - it isn't always
> > > > > convenient or safe to shift in competition.
> > > > >
> > > > > Sufficient torque is required to get the car moving and
accelerating,
> > but
> > > > > it is power that determines how fast the speed (RPM) of the engine
can
> > > > > change. So, yes, a high torque car can break the tires loose with
a
> > gas
> > > > > pedal application, but that does not imply that it is necessarily
> > > > > accelerating (changing velocity) quickly.
> > > > >
> > > > > That said, it's probably pretty clear that I like a rev happy
motor in
> > a
> > > > > car. I take the opposite fence on a motorcycle where I go for low
> > rev'g
> > > > > torque monsters, but I'm no motorcycle racer either.
> > > > >
> > > > > So, SU v. Solex carbs on our Roadsters:
> > > > >
> > > > > It was argued that because the SUs are only supplying one cylinder
at
> > a
> > > > > time, they can be compared with Solex's based on inlet diameter.
This
> > > > > suggested that the SUs 46mm were larger than the Solex's 44mm
inlets.
> > > > >
> > > > > The problem here comes from two variables not considered. One is
> > engine
> > > > > RPM. At 3000 RPMs, each cylinder is firing 1500 times per minute
or
> > 25
> > > > > times per second. That suggests a lot of direction changes for
the
> > > > > airflow in the SUs, slowing the velocity of the air flow on a
cylinder
> > by
> > > > > cylinder basis. Then, since the SUs feed two cylinders, the air
flow
> > path
> > > > > is not straight - further slowing the velocity of the intake air.
> > > > >
> > > > > So, the Solex's 44mm inlet definately flows a larger volume of air
> > > > > allowing it to stuff a larger combustible charge in each cylinder
than
> > the
> > > > > SU's shared 46mm inlet. And, I'm betting the intake duration on
the
> > Solex
> > > > > Cam reflects this improved ability to charge the cylinders.
> > > > >
> > > > > The other difference is the shape of the intake path. The faster
flow
> > > > > through a straigt path (like the Solex) leads better high RPM
> > performance.
> > > > > The slower flow through a curved path (like the SUs) leads better
low
> > RPM
> > > > > performance.
> > > > >
> > > > > Personally, I think my SU 2000 is a little anemic above about
4.5k.
> > And,
> > > > > since it is easy to tach up a car by downshifting and getting into
the
> > > > > power band when needed - I'd like to move it up into the Solex
type
> > > > > territory. So, just some ramblings. Let me know if there are
holes
> > in
> > > > > this reasoning, 'cause the investment is significant. The returns
> > don't
> > > > > seem cost effective from a 15hp gain perspective - but the change
in
> > the
> > > > > power curve justifies the expense (that is, if I ever get the $)
for m
> > e.
> > > > >
> > > > > Top Down in Houston,
> > > > > Milton and the BeautyQueen
> > > > >
> > > > > /// datsun-roadsters@autox.team.net mailing list
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> > > >
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>
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