Lotus Europa Twin Cam User manual

LOTUS EUROPA TWIN CAM
COMPETITION MANUAL
PREPARED BY: JENSEN MOTORS, INC.
19200 SUSANA RD.
COMPTON, CALIF. 90221

( i )
FOREWORD
Modifications of the type described in this booklet and/or the use of the Lotus Europe Twin-Cam
for competition render the vehicle warranty null and void. Jensen Motors, Inc. and/or Lotus Cars,
Ltd. will not be held responsible for any damage or injury, which may occur in the following of
any procedure or changes outlined in the following text.

( ii )
CONTENTS
FOREWORD............................................................................................... ( i )
INTRODUCTION....................................................................................... ( ii )
Section
CHASSIS...................................................................................................... 1
SUSPENSION AND STEERING................................................................ 4
BRAKING SYSTEM................................................................................... 11
COOLING SYSTEMS (WATER, OIL AND DRIVER)............................. 12
ENG I NE..................................................................................................... 14
TRANSMISSION AND CLUTCH.............................................................. 15
BODY........................................................................................................... 21
ELECTRICAL.............................................................................................. 21
FUEL SYSTEM............................................................................................ 22
GENERAL.................................................................................................... 22
SETTING-UP CAR...................................................................................... 23
SPECIFICATIONS....................................................................................... 24

( iii )
INTRODUCTION
The advanced design and performance of the road equipped Lotus Europa Twin-Cam
precludes the necessity for extensive modifications for track purposes. The modifications made
were mainly as a result of necessary compromises incorporated in the road car to conform to
regulations and to achieve an acceptable level of creature comfort. Other modifications were
necessary to increase the safety of the car and driver while racing.
We do not claim the modifications and changes mentioned in this booklet to be a
complete listing, or to be the ultimate in development; but merely those which we have proved to
be effective in campaigning the car in SCCA production sports racing. While we would not
knowingly recommend changes, which would not be legal under the SCCA production sports
rules, it is the responsibility of each driver to ensure that his vehicle conforms to the applicable
competition regulations.
We would like to wish you every success in your competition endeavors with the Lotus
Europa Twin-Cam, and if technical assistance is ever required please do not-hesitate-to contact
the writer.
Colin Ham
Service Engineer
Jensen Motors, Inc.
19200 Susana Road
Compton, California 90221

1
CHASSIS
In order to provide maximum safety for the driver a full roll cage was added to the basic
chassis. The backbone type design of the chassis necessitated a very unorthodox and intricate
cage. (See Figure 1.1A and 1.1B)
The cage was bolted rather than welded to the chassis at several points to allow removal
of the body from the chassis, although the cage could not be removed intact from the body. The
two main roll over hoops were bolted to the chassis main backbone with bracing stays forward to
the front crossmember and rearward adjacent to rear spring supports. Threaded reinforcement
plates were added to the chassis at the attachment points. The rear spring supports were
reinforced and welded rather than bolted to the chassis. This necessitated
fabrication of a removable rear chassis crossmember to facilitate engine removal.
The complete cage was enclosed within the bodywork in order to maintain the
appearance and the good aerodynamic characteristics of the car.
Torsional stiffness of the front crossmember-backbone intersection was increased by
calculated positioning of roll cage attachment points. All welded joints on the standard chassis
were filled to give continuous welds for added strength.
No attempt was made to lighten the chassis as it was considered to be as light as practical.

2

3

4
SUSPENSION
Front Suspension
The front suspension uprights and hubs were from the Triumph GT6 Mk II!, to enable
the use of larger 9 3/4 in. d i3meter brake discs and calipers from the same car.
The suspension arms inboard rubber bushings were changed to "Nylatron" (Holy
Disulphide) bushings to eliminate any uncontrolled movement in the suspension. All bushings
are identical and eight are needed per car. The dimensions are: length=l.40 in., diameter=l.061 in.
with bore=0.502 in. The bushings are a "press-fit" in the suspension arms.
The suspension was lowered by fitting shorter front springs together with fully adjustable
Koni shock absorbers. It should be noted, that due to the large deflections required in relation to
spring length, special thin vanadium spring wire must be used to prevent the spring becoming
coil bound on full bump. The shock absorber bump rubber must be shortened approximately one
inch to prevent fouling on full bump.
With the lowered suspension settings, it is necessary to decrease the negative camber of
the front wheels. This was achieved by moving the lower suspension arms outer pivot point
inwards. This was carried out by slotting the existing holes in the arms and installing drilled
plates to locate pivot in desired position (0.158 in. per l° of camber change). The plates fitting
securely in channel of lower suspension arms.

5
The optimum size of the front sway bar was found to be 7/8 in. in diameter. The bar was non-
adjustable and installed in approximately the stock location. The sway bar had Fabroid rod end
spherical bearings on each end and was attached to the lower shock absorber mounting bolts
using spherical bearings. The standard location arms were shortened to compensate for the
lowered suspension. (See Figure 2.1) All fine suspension tuning was achieved by use of an
adjustable rear sway bar.

6
Rear Suspension
The modifications made to the rear suspension consisted of mainly eliminating rubber
mounting bushings and strengthening chassis attachment points. Full adjustment capability was
also provided. An adjustable sway bar was added to enable fine suspension adjustments to be
made to compensate for different circuits. (See Figure 2.2A and 2.2B)

7

8
The trailing arms were relieved to provide clearance for the wide section Goodyear
cantilever-type tires and wide wheels. The rubber chassis mounts were changed to "Fabroid"
bearings and the trailing arms were modified to accept the "Fabroid" bearing rod-ends. Stiffening
plates and reinforcement brackets were added to the chassis at the trailing arms attachment points.
Care must be taken when installing the trailing arms to ensure there is enough angularity on the
"Fabroid" bearings- tapered spacers and shimming washers between the bearings and the chassis
are required, Wheel alignment is achieved by adding or removing shimming washers. (See
Figure 2.3A and 2.36)
The standard rear hubs and uprights were utilized with the uprights drilled to accept
the brackets for the rear sway bar reaction links. (See Figure 2.2)

9

10
The rear stub axles were installed using "Loctite Shaft and Bearing Mount" on the threads.
The locking nut was torqued to 160 lbs ft. The hubs should be checked for tightness after every
track session as problems have been experienced with stretching and consequent slackening of
the axle shaft nut. It is recommended that the stub axles be replaced after three practice and race
sessions as a precautionary measure.
The rubber bushings in the transverse links were replaced with "Fabroid" spherical
bearing rod ends at each end, The rear wheel camber could be adjusted by changing the effective
length of these transverse links. The inboard mount on the gearbox was strengthened to give
more positive location.
Lowering of the rear suspension was achieved by using shorter springs and Koni shock
absorbers. Approximately 1 in. of the bump rubber must be removed from the shock absorber to
enable the lowest ride height to be used.
Steering
The standard steering rack was found adequate but it was found necessary to use Fabroid
rod end spherical bearings on the tie rod ends. These bearings were installed on top of the
steering arms together with shims to minimize bump steer. (See setting up section.) The standard
rack mounting brackets and location was-retained. The column was lowered for increased driver
comfort.

11
BRAKING SYSTEM
The standard vacuum assisted tandem master cylinder was replaced by separate non-assisted
master cylinders for the front and rear brakes. The two master cylinders were coupled by means
of an adjustable, pivoted cross-bar to enable front to rear brake balance to be changed. Due to the
proximity of steering rack, it was necessary to mount one master cylinder at 45° and utilize
remote brake fluid reservoirs.
A new clutch and brake pedal assembly was fabricated togive improved pedal positions
for heel and toe operation. A hydraulically operated clutch was used which employed a similar
master cylinder and remote fluid reservoir.
The front brake discs were replaced by the 9 1/4 in. diameter discs from a Triumph GT 6
Mk. III This is a direct substitution of existing front uprights, hubs, calipers, etc., with those from
the GT 6. Brake cooling was assisted by ducting air from air inlets in the front spoiler.
The rear brakes were changed to twin-leading shoe type with two wheel cylinders per
brake. These brakes are approximately 40 percent more powerful and give the car more balanced
braking. The back plates are of Girling manufacture and were standard fitment on the front of
early Sunbeam Imp's. (Similar backplates are found on the front of early Triumph Herald's.) It
was necessary to slightly modify the backplates so as to fit-the

12
1 ½ in. width brake shoes and still maintain the desired rear track dimension. This entailed
recessing center of plate approximately 1/8 in. so that shoes were 1/8 in. closer to center of the
car. (Same position as with standard backplates.)
Aeroquip steel braided brake lines were used throughout and routed through the cockpit
to prevent damage and facilitate inspection.
COOLING SYSTEMS
Water Cooling
The standard radiator in conjunction with the engine oil coolers used was found to be
adequate even when racing in ambient temperature as high as l15°F.
The electric fan was discarded and aluminum ducting fabricated to divert all airflow
through the radiator. Aluminum tubing was substituted for the steel water tubes running through
the chassis backbone. The 15 psi pressurized system-utilized an expansion tank and 50 percent
Ethylene Glycol coolant with inhibitors. The system was filled through a threaded cap in the
thermostat housing. The-capillary type temperature gauge sensing bulb was mounted in the top
radiator tank. Care must be taken to ensure all air is evacuated from the system.

13
Oil Cooling
It was found essential to use two front mounted oil coolers from an MGB (Part No. ARO
9809). The coolers were mounted in tandem in the side of the radiator ducting. The air from the
coolers was ducted out underneath the car through an opening cut in the floor of the nose.
(Consult SCCA GCR pertaining to oil cooler ducting limitations.)
The oil lines to the coolers were routed through the chassis backbone for safety purposes.
A chassis mounted filter was used with the oil temperature being monitored at the filter head.
The standard oil pump was retained with a higher relief valve setting.
Driver Cooling
The left headlight aperture was used for driver cooling (essential in high ambients) and to
supply cooler air for engine breathing. A six inch duct was routed from the headlight opening
through the cockpit, with an outlet for driver air, and thence through the firewall to a cold air box
on the carburetors.

14
ENGINE
The capabilities and limitations of the Ford-based Lotus Twin-Cam are well known.
Therefore, no attempt has been made to detail any engine modifications. The power output is
severely restricted by the limited amount of substitution and modifications allowed under the
SCCA Production sports rules.
All engine preparation was carried out by John Shankle of Shankle Automotive
Engineering, Van Nuys, California, who we have always found to be extremely helpful and
cooperative. The engine used was a non-emission controlled version utilizing twin Weber 40
DCOE carburetors with an eight port cylinder head.
It was found necessary to increase oil-pan ventilation as there was a tendency for an
excessive amount of oil to be pumped into the oil catch tank with the standard ventilation system.
The problem was cured by an additional breather on the mechanical fuel pump blanking plate.
The four into one exhaust manifold was manufactured by Kurt Andress of Costa Hesa,
California, and featured a low mounted tail pipe. The dynamometer developed tail pipe length
would protrude approximately six inches beyond the rear of the body, thus the tail pipe was
routed to the left rear corner. This helps to minimize possible damage caused by over exuberant
competitors nudging the rear of the car.

15
TRANSMISSION
Clutch
A single plate, Borg & Beck competition clutch was used in conjunction with a specially
manufactured aluminum flywheel. A hydraulic actuating mechanism was employed in place of
the standard cable system. This was found necessary due to excessive pedal pressure as a result
of the stronger diaphragm spring or the competition clutch.
The master cylinder was mounted adjacent to the brake master cylinders on the front
crossmember. A remote reservoir was necessary due to proximity of steering rack and radiator.
(Car was R.H. drive.) The slave cylinder was mounted on a fabricated bracket attached to the
bell housing. It was necessary to shorten and rotate actuating arm approximately 180° to accept
the adjustable pushrod from the slave cylinder. An adjustable stop was incorporated on the slave
cylinder mounting bracket to prevent clutch overthrow. Clutch ventilation was increased by
removing lower flywheel splash guard.
The spigot shaft supplied with the straight cut, close ratio gears has standard SAE splines
to mate with the Borg & Beck clutch plate. If the standard spigot shaft is used it will be
necessary to modify the center of the clutch disc to accept the metric splines. The easiest method
is to weld the center from