Martin,

As you probably know, bump steer is caused by the differing geometry
of the steering system and the suspension system as the suspension
moves from it's lowest point to it's highest point.? As the
suspension moves up and down so does the tie rod (steering outer
rod).? If the hinge points for the suspension and the tie rods are
not fairly close to each other in a vertical plane (if the tie rod
is much longer or shorter than the suspension length) then the
length of the of the tie rod vs the distance of the upright
attachment point for the tie rod from the chassis will be
different.? Therefore, when the suspension moves through it's range,
the uprights will be steered out or in based on the movement of the
suspension.? This can drastically change the toe adjustments as the
suspension moves.? My 23 has a very slight bump steer during a large
movement of the suspension but I do not notice this while driving as
it is equal on both sides.? The problem comes when you have one side
steering in bump while say going over a curb.? This makes the car
jerk quickly from one side or the other as the suspension moves.?

What I would do is to set up a bump steer measuring system.? What I
do is to remove the spring/shock and tire on the front suspension.?
Then I clamp a mirror to the brake rotor.? Then you get one of those
cheap laser pointers and aim it at the mirror directly from the side
(90 degrees to the chassis at the center of the front suspension) so
that the laser beam contacts the mirror during the complete
suspension movement.? Then make up a large piece of cardboard with
vertical lines about 2 in. apart and set this just outside of the
laser.? Then when you move the suspension up and down, the laser
beam will contact the mirror and shine on the cardboard.? As you
move the suspension, you will see if there is any movement of the
rotor to the right or left because of the dot moving right and left
on the cardboard.? Now you can move the steering rack or adjust the
steering arms attachment points to the uprights and see how this
affects bump steer.? When you get it so the dot pretty much stays
between the 2 inch lines for both sides in the front, you generally
have things where you want them.? This set up will allow you to
quickly try different configurations of the steering to see how to
adjust things to minimize bump steer.? You can also use this system
on the back to see if the rear suspension has bump steer.?

If you have any other questions, please let me know.

Don Stark

---

YAHOO! GROUPS LINKS

• ?Visit your group "" on the web.
  ?
• ?To unsubscribe from this group, send an email to:
  ?L23Registry-unsubscribe@...
  ?
• ?Your use of Yahoo! Groups is subject to the .

---

Send instant messages to your online friends http://au.messenger.yahoo.com

Martin,

As you probably know, bump steer is caused by the differing geometry
of the steering system and the suspension system as the suspension
moves from it's lowest point to it's highest point. As the
suspension moves up and down so does the tie rod (steering outer
rod). If the hinge points for the suspension and the tie rods are
not fairly close to each other in a vertical plane (if the tie rod
is much longer or shorter than the suspension length) then the
length of the of the tie rod vs the distance of the upright
attachment point for the tie rod from the chassis will be
different. Therefore, when the suspension moves through it's range,
the uprights will be steered out or in based on the movement of the
suspension. This can drastically change the toe adjustments as the
suspension moves. My 23 has a very slight bump steer during a large
movement of the suspension but I do not notice this while driving as
it is equal on both sides. The problem comes when you have one side
steering in bump while say going over a curb. This makes the car
jerk quickly from one side or the other as the suspension moves.

What I would do is to set up a bump steer measuring system. What I
do is to remove the spring/shock and tire on the front suspension.
Then I clamp a mirror to the brake rotor. Then you get one of those
cheap laser pointers and aim it at the mirror directly from the side
(90 degrees to the chassis at the center of the front suspension) so
that the laser beam contacts the mirror during the complete
suspension movement. Then make up a large piece of cardboard with
vertical lines about 2 in. apart and set this just outside of the
laser. Then when you move the suspension up and down, the laser
beam will contact the mirror and shine on the cardboard. As you
move the suspension, you will see if there is any movement of the
rotor to the right or left because of the dot moving right and left
on the cardboard. Now you can move the steering rack or adjust the
steering arms attachment points to the uprights and see how this
affects bump steer. When you get it so the dot pretty much stays
between the 2 inch lines for both sides in the front, you generally
have things where you want them. This set up will allow you to
quickly try different configurations of the steering to see how to
adjust things to minimize bump steer. You can also use this system
on the back to see if the rear suspension has bump steer.

If you have any other questions, please let me know.

Don Stark

Martin:

Your welcome and I have more photos of a restoration in progress if you need them. I enjoyed the race at Ruapuna particularly since there was such a wide diversity of cars entered. I took a good number of pictures that I subsequently shared with my racing mates, several of which have raced in the Southern Festival of Speed. Happy Holidays.

Gary


From: Martin Lucas <marty7_nz@...>
Reply-To: L23Registry@...
To: L23Registry@...
Subject: Re: [L23Registry] Twincam Engines
Date: Mon, 26 Dec 2005 00:27:41 +1300 (NZDT)

Hi Gary,

Thanks for the photos and information. It is a great help.

Would you believe that I was at the Ruapuna event (Southern Festival of Speed) three years ago as well. Thinking of heading down for the coming event to support a friend. It's a small world.

Martin,

Gary Horstkorta <horsty@...> wrote:
Martin:

Hello. Your 23 projects sounds like fun and I have a good idea what you are
going through as I restored my 23B, frame up, five years ago. When I
purchased the car, the owner gave me a set of photos taken by someone else
of a restoration in progress. I used these photos as my "bible" when
restoring the car as they show excellent detail of the frame, suspension,
etc. I would be happy to provide a copy of these to you but since there are
a good number, I think it best to mail them. If interested, please email
your mailing address off-line.

Regarding your drysump tank, I'll email some photos as my tank is out of the
car while the engine is being rebuilt. I'll also take photos of the tank
bracket. By the way, will you be using the frame tubes for water/oil or
running seperate lines?

My engine (1600cc Twin Cam) lasted twenty-seven race meetings before
requiring the current rebuild. Like Don, I keep the rpms under the maximum
redline by 500-1000 which apparently has had the desired affect of longer
life. By the way, will you be using the frame tubes for water/oil or
running seperate lines?

I have attached one photo with this email which I took three years ago while
attending a vintage event at Ruapuna near Christchurch. The fellow in the
replica 23 had built the car and did a very nice job.

Best Regards,

Gary
Send instant messages to your online friends

_________________________________________________________________
Dont just search. Find. Check out the new MSN Search!

Send instant messages to your online friends http://au.messenger.yahoo.com

Martin:

Hello.? Your 23 projects sounds like fun and I have a good idea what you are
going through as I restored my 23B, frame up, five years ago.? When I
purchased the car, the owner gave me a set of photos taken by someone else
of a restoration in progress.? I used these photos as my "bible" when
restoring the car as they show excellent detail of the frame, suspension,
etc.? I would be happy to provide a copy of these to you but since there are
a good number, I think it best to mail them.? If interested, please email
your mailing address off-line.

Regarding your drysump tank, I'll email some photos as my tank is out of the
car while the engine is being rebuilt.? I'll also take photos of the tank
bracket.? By the way, will you be using the frame tubes for water/oil or
running seperate lines?

My engine (1600cc Twin Cam) lasted twenty-seven race meetings before
requiring the current rebuild.? Like Don, I keep the rpms under the maximum
redline by 500-1000 which apparently has had the desired affect of longer
life.?? By the way, will you be using the frame tubes for water/oil or
running seperate lines?

I have attached one photo with this email which I took three years ago while
attending a vintage event at Ruapuna near Christchurch.? The fellow in the
replica 23 had built the car and did a very nice job.

Best Regards,

Gary

Send instant messages to your online friends http://au.messenger.yahoo.com

As the Registrar for the Lotus 23, I am concerned about originality.
(Originality may be like the question of the Emperor's clothes. One
should not discuss it.)

But the question of what 'originality' means is difficult to answer.
It is a fact that every single part of a Lotus 23 can be had on the
current market. So one can, and some builders are, producing
replicas of Lotus 23s. And I suspect strongly that some cars built
from scratch have been passed off as original Lotus 23s.

Then too, I don't believe even the best maintained Lotus 23 will come
to a new owner with enough data to verify that each part is factory
original, or in the alternative, when it was replaced and the source
of the replacement. Every Lotus 23 of which I know has had a long
list of owners. And may they all have enjoyed their ownership as
much as I did.

Let us suppose that a Lotus 23 has crashed and the chassis, body and
some suspension parts have been replaced. Is the car
still 'original'? Some say yes, so long as the car has been
maintained with 'correct' replacement parts it is 'original'. Of
course, Lotus long ago stopped making factory original parts. Even
such things as twin cam cylinder heads are no longer factory
original. And the wobbly-web wheels that came on the Lotus 23 and
other Lotus cars are not now available from the factory.

In fact, when I bought my Lotus 23 back in the early 1980s, my first
concern was where to get the parts I needed to restore the car
to 'original' condition. I found some 'original' parts on the
market, found drawings and made others after I taught myself to do
braze-welding, and I bought some newly made parts. Further, I made
parts for other owners. After all of this, I thought I had done a
decent job of restoration of my Lotus 23 to close to original
condition.

Some restorers will tell you that an original chassis, now some forty
years old, is unsafe and should be replaced for racing. The January
issue of Victory Lane has an article that pretty much says that
original wheels are also unsafe. If these parts are unsafe to race,
what about suspensions, springs, and all the rest? Shall we just put
all the original parts in a museum and build replica cars to race?
And if that is the case, just how long shall we allow these new parts
to be raced?

Not long ago there was an article in Victory Lane (I have forgotten
who wrote it.) that said - more or less - that so long as one simply
replaced worn or damaged parts of an original car, the car should be
considered 'original'. That is the "Grandfather's Axe" answer to the
question of originality. Perhaps the best criterion is to say that
the history of the car prevails. If one has a complete - or nearly
complete - history of the car, tracing it back to a time when
replication would not have been done, then one could say the car is
original. I think that is what the author of the article had in mind.
I agree with it.

Comments are solicited.

Bill Steagall
Registrar

Mike,

I'm sorry to say that I do not live in the bay area. I live in Orange
County in Southern California. You are welcome to stop by any time
you are in the neighborhood. Also, I try to attend the Wine Country
Classic at Sears Point and the Monterey Historics at Laguna Seca. If
you attend those races, stop by and say hi.

Gary Horstkorta lives in Livermore and has a great looking 23 as
well. His car is the red one in the pictures I put on this site.

Don Stark

Bill,

Thanks for your input. I would think that if you regularly went to
8500 rpm, 18 hours would be prudent. Shifting at 7500 should be much
easier on the engine. I'm going to go another year and we will see
what happens. My engine builder says the bottom end is pretty stout
and normally it is just a loss of performance.

Don Stark

Martin,

I'm sure your car will be ready before you know it. If you would like
to give me your direct e-mail, I can take some pictures of my oil
tank, pedals, radiator mounts, fuel pump brackets, etc. and mail them
directly to you. That might help you locate things. Just let me know
what you want pictures of. Bye the way, my fuel tank is on the left
side pod and not behind the seats. It is nice because it balances out
the drivers weight.

Making the engine last another year has to do with the normal fiscal
restraints. I'm a one man band (owner/driver/mechanic) and do not
have tons of money to spend on this hobby. Not to mention that my
group has a 2.5L Porsche powered Bobsi, V8 McKees & Lotus 19s, a
1700cc (?) Alfa powered Legrand, (all these cars have big wide tires)
2.0L Elva Mk7s and Mk8s, etc. so I seen no need to work the engine too
hard to keep up. I'm not trying to win a championship or going from
vintage racing to F1 or anything. I am 58 years young and am happy
just to get out amongst them. I also want a reliable motor. So far,
I have changed the oil, checked the timing, changed the plugs and
adjusted the carbs in the last three years. The motor has never let
me down. Lately I have had to make sure that the oil catch tank is
empty as I am dumping a little more crankcase pressure overboard.
I'll make sure it is empty before each weekend.

Keep in touch and get those pictures up.

Don Stark

Martin:

Hello. Your 23 projects sounds like fun and I have a good idea what you are going through as I restored my 23B, frame up, five years ago. When I purchased the car, the owner gave me a set of photos taken by someone else of a restoration in progress. I used these photos as my "bible" when restoring the car as they show excellent detail of the frame, suspension, etc. I would be happy to provide a copy of these to you but since there are a good number, I think it best to mail them. If interested, please email your mailing address off-line.

Regarding your drysump tank, I'll email some photos as my tank is out of the car while the engine is being rebuilt. I'll also take photos of the tank bracket. By the way, will you be using the frame tubes for water/oil or running seperate lines?

My engine (1600cc Twin Cam) lasted twenty-seven race meetings before requiring the current rebuild. Like Don, I keep the rpms under the maximum redline by 500-1000 which apparently has had the desired affect of longer life. By the way, will you be using the frame tubes for water/oil or running seperate lines?

I have attached one photo with this email which I took three years ago while attending a vintage event at Ruapuna near Christchurch. The fellow in the replica 23 had built the car and did a very nice job.

Best Regards,

Gary




From: Martin Lucas <marty7_nz@...>
Reply-To: L23Registry@...
To: L23Registry@...
Subject: Re: [L23Registry] Twincam Engines
Date: Sat, 24 Dec 2005 09:32:04 +1300 (NZDT)

Hi Don,

Thanks for the words of encouragement. Still a long way to go before it is drivable, certainly looking forward to that moment.

From your comments it certainly looks like you have a 8000-9000 rpm engine, and yes, more wear will take place as the engine speed increases. It sounds like you are happy to leave it as is and race another year. Makes sense to me. What you can do is keep an eye on the engine vent/catch tank. As the rings start to go it will pressurize the engine, thereby blowing more oil out the vent hose.

The 'stock' twin cam is similar here in NZ. Not many run on OE parts. A lot now run datsun steel cranks. There is a real assortment of engine specifications. A mixture of later 1600 stroke cranks, 1600 Ford blocks. And some that run the L block with the longer stroke crank, twin cam rod, and forged pistons. The most reliable engines seem to be the ones with 83.5mm bore, and cams in the 6000 to 7500 range. Oh, and driver. One friend has manged to go through three engines in one car for various reasons.

I will post some pictures. At the moment I'm busy making the swirl pot and trying to work out how they were mounted. Every car I see photos of looks different in the detail. I am also trying to see the detail of the tube work up by the pedals on the radiator side. I think a few tubes are missing. I have already removed the front alloy panel to lower the pedals so have the golden oppertunity to add the tubes if neccessary. I am also trying to work out how the fuel tank located behind the seats was mounted. I have decided to double panel the cockpit sides (to increase chassis stiffness). Before I do this I want to get all the brackets there. I also can not work out how the fuel pump and filter were bracketed in the lower left of the engine bay.

Thanks,
Martin.


Send instant messages to your online friends

_________________________________________________________________
Dont just search. Find. Check out the new MSN Search!

Send instant messages to your online friends http://au.messenger.yahoo.com

Martin,

Thanks for your reply about the engine. I hope you get your replica
done soon. You will love driving it. I believe my car to be an
original chassis but there are many cars that I race against that are
pretty much new top to bottom. New or old they are just as much fun
to drive.

I guess some more information on my engine is appropriate. 7500-8000
rpm was about right for the original engines with stock cranks and
rods. My engine like most of the "stock" twincams in the USA has a
billet crank, Carillo rods and racing pistons. According to the
engine builder it is quite capable of going to 9000 rpm. As for the
power band, it is just getting going at 7500 and I have to be careful
that I don't fall out of the lower end of the power band shifting up
too soon. The engine loves to rev. I was passing a V8 once and let
it go, shifting about 8700, and it was very happy and was really in
the meat of the power band in the next gear. I shift at 7500 as a
means of getting the engine to last a bit longer. I have been told
that high revs are what wear them out quickest. My engine builder
also says that the thing that wears out first are the rings but with
the compression/leak down I have, I would think that things are pretty
much ok in that regard. The engine puts out about 185 hp. I might
loose a little response and a few hp by not freshening it up but
stretching it another year will help the budget.

Put some pictures of your car on the site so we all can see it.
I will try to get some pictures of my oil tank for you.

Don Stark

开云体育

Ted Wenz and Peter Marcovicci like to have the engine back after 18 hours of racing.?? They see problems coming if you run them longer, especially at 8500+ rpm.? I am afraid to see how long it will last if I don't take it back after 18 hours.? I would not run it another year.

?

???????????????????????????????????????????????????????????? Merry Christmas,

?

???????????????????????????????????????????????????????????????? Bill Hollingsworth

Send instant messages to your online friends http://au.messenger.yahoo.com

Merry Christmas and a Happy 2006 to you all.

I would love to see pictures of all your cars. I am sure you all
must have some pictures. It is easy to scan in an image and then
put it on this Yahoo site. You can open up your own folder to store
your pictures and then display all the pictures you would like. You
can see mine by just going to Photos and clicking on Don Stark's
photos. Let's all try to do this in the near future so we can see
each others cars. It would also be nice to see the front and rear
of the car with the body off or flipped up so that we can compare
the layout of tubes and equipment. This site is a great resource
and we should use it more.

I have a question for those of you out there with some engine
experience. How many hours can you run a 1600cc Lotus twincam motor
before you need to have it refreshed or rebuilt? How does it affect
it if you run it to 8500-9000 rpm as opposed to shifting it at 7500-
8000 rpm? Where does one come up with a good block and head for a
backup motor? As you can see, I have some decisions to make. My
engine has about 24 hours (that's racing time) on it and my engine
builder has said it needs going through. But, he also said that if
I shifted at 7500 rpm, it would last forever! It has 175, 175, 175,
180 lbs of compression and the leakdown is 6%, 6%, 4%, 2%. I have
been running Mobile 1 20w50 at all times. My feeling is that if it
has no metal in the filter, I sould run it another year. What do
you think?

I look forward to hearing from you.

Don Stark

When I bought my 23 (not a B) from Ed Brannon in 1997, the diagonal tube over the driver's legs had been removed. I was told this was a common modification for the reason explained by Gary. Indeed, the several 23s I looked at when shopping for the 23 tended to have this modification.

Since I am about "Chapman height," I thought I would reinstall the missing tube in my 23, which still has the original frame. I had some period photographs of the frame section as well as drawings supplied by some friends. Ed Hullinger (who then ran a racing shop in Los Angeles, California) did the work for me and did a great job, down to the fixture for the spare wheel.

And no I have never carried a spare!

Regards to all.

Andres
Manila

Bill:

Ha, a spare tire? The only one is around the waist of some of the drivers!

Gary


From: William Steagall <steagall99@...>
Reply-To: L23Registry@...
To: L23Registry@...
Subject: Re: [L23Registry] Re: Chassis modification
Date: Thu, 8 Dec 2005 16:38:24 -0800 (PST)

Hi, all!

I've been looking at my older email again.

This one reminded me that I have heard that the mentioned bar was often removed to make room for the knees of taller drivers. (Remember, the specification for an English driver was ten stone and 5' 9".)

Does anyone carry a spare tire? Ever?

Bill Steagall

silvenm <Nigel@...> wrote:
Thanks to you all for your input....it sounds like this is quite a common modification and I'd be very interested to see some pictures of how it's done.

As my business address is public domain I'll publish it here and if anyone can send me a photo or two then I'd be very greatful.

Nigel Silverthorn
Xanthos Sports Cars
8 Tarragon Place
Bradley Stoke
Bristol
BS32 8TP

www.xanthoscars.co.uk

Many thanks and I look forward to seeing them.
Best regards
Nigel

--- In L23Registry@..., "Gary Horstkorta" <horsty@m...>
wrote:

Nigel:

I think I have seen such a frame/car as you describe which belongs to a

vintage racer here in Northern California. I also have heard of other 23 owners who have removed the diagonal tube running from the bulkhead
on the drivers side to the left front junction of the main frame. This was replaced by either one or two tubes which meet at the top of the scuttle and extend down to the cross tube at the front of the chassis. As you indicated, the spare tire mounting is lost but there certainly is more knee room.

At 6' 0" and 215 lbs. I fit snuggly into my 23 but I have the advantage

of shorter legs and a longer upper body. Even at that I have padding on the

standard cross brace in the footwell to protect my right leg and

rely on the "dead pedal" quite a bit during a race.

I will let you know if I am able to contact the 23 owner mentioned in the

first paragraph.

regards,

Gary

From: "silvenm" <Nigel@s...>
Reply-To: L23Registry@...
To: L23Registry@...
Subject: [L23Registry] Chassis modification
Date: Tue, 22 Jun 2004 09:12:00 -0000

Yahoo! Groups Sponsor ADVERTISEMENT


---------------------------------
Yahoo! Groups Links

To visit your group on the web, go to:


To unsubscribe from this group, send an email to:
L23Registry-unsubscribe@...

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

_________________________________________________________________
Dont just search. Find. Check out the new MSN Search!

开云体育

Hi all.? For preventing the corrosion of the aluminum twin cam head one needs to add a tea spoon of Potassium Chromate to the water system with your normal additive of water pump lube.?Without the Potassium Chromate the water system become a battery, electrolysis occurs, and the aluminum head corrodes.? With it, the water holes in the head look as new.? Antifreeze and racing on the track do not mix.

?

??????????????????????????????????????????? Merry Christmas,

?

???????????????????????????????????????????????????????? Bill Hollingsworth

?

?

The Potassium Chromate can only be gotten through a supplier to labs.? Your sons/daughter's science lab at school would have it and could get it for you.

开云体育