Elite/Eclat/907 history (2 articles)

Engine development

The Mk 62's 904 engine was a development mule for the 907, and was a composite of a Vauxhall 2 litre iron-block assembly, a Lotus-spec'd, longer stroke crank and a Lotus prototype cylinder head. Lotus recognized that the most development intensive part of the engine design was going to be the head. To expedite head development without waiting for the complete engine to be designed and prototyped, they "borrowed" the cylinder block from the very similarly sized/configured (slant four) Vauxhall Victor 2.0 and mated it to the prototype head.

Later, the Mk 62 received the 906 engine, which was a further development of the Lotus design with a prototype sand-cast aluminum block. The 906 eliminated the Vauxhall crutch that had allowed the development program to get a faster jump start and got the engine closer to it's final, all-Lotus design.

The Mk 62 car was built as much as a development test bed for the new engine as a race car. It was felt that racing the engine would accelerate the learning curve.

I've read somewhere or other that the 900 family block is actually quite different from the Vauxhall block, despite having the same bore centers, and that the fact that they have the same bore centers was just a coincidence.

The aluminum 907 block is very different from the iron Vauxhall block and not just an alloy adaptation of an existing design. However, it's probably (I'm jumping to a conclusion) more than coincidence that the bore centers are the same. The head was first designed to fit the Vauxhall block. Once that was done, why incur the extra work of re-designing it to fit a different bore spacing? Just design your new block to fit the head that was developed in advance of the rest of the program.

904 Iron block 2.0 race engine with T-J fuel injection, July '68 (aka, LV220=Lotus-Vauxhall, 220 Bhp)
905 Iron block 2.0 road car engine (non-production, test only)
906 Sand-cast aluminum block 2.0 race engine (aka, LV240)
907 Die-cast aluminum block 2.0 road car engine
908 Aluminum block 4.0 V8 race engine
909 Aluminum block 4.0 V8 road engine
910 Die-cast aluminum block 2.2 Turbo road car engine
911 Die-cast aluminum block 2.2 N/A Sunbeam-Talbot engine
912 Die-cast aluminum block 2.2 N/A Lotus road car engine

The 904 had a 95.25mm (3.75 in) bore x 69.85mm (2.75 in) stroke for a 1995 cc displacement... just under the racing class limit. The similar Vauxhall Victor 2000 used the same 95.25 bore, but a shorter 69.25 stroke for a 1975 cc displacement. As installed, the 904 crank was a Lotus specific part; however, I don't know if it was machined from a Vauxhall blank or made from scratch.

Later, the 907 used the same 95.25 (3.75) bore as the Vauxhall, but with a claimed 69.2 (2.72) stroke/ 1973 cc displacement. Just a weeee bit smaller than the Vauxhall engine. The Elite/Eclat/Esprit manuals give the bore dimension to 4 decimal places, but leave the stroke at 69.2 (2.72).

I wouldn't doubt (but I don't know) that the stroke and displacement numbers (.05mm / 2cc smaller than the Vauxhall) were more of a weak marketing attempt to give the 907 it's own non-Vauxhall identity by simply rounding off the numbers.

The 907 was supposed to be an important step for Lotus in establishing itself as a stand-alone manufacturer. However, when Lotus fast-started it's development program by basing the first prototypes on the Vauxhall block, the press grabbed onto the Lotus-Vauxhall identity with a death grip and Chapman couldn't break it. After a while, hearing the press continually refer to his new engine as a Vauxhall or Lotus-Vauxhall started to SERIOUSLY rub Chapman the wrong way.

Prior to the M100 Elan, no LOTUS that saw the light of day used a transverse engine.

In accordance with that, all LOTUS Europa's and it's variations used longitudinal engines and transmissions. The GKN 47D used the Rover / BOP aluminum V8 mounted north-south.

The transverse engined Europa/Mk 62 that got so much attention on this list a while ago is an aftermarket project... Banks Service Station I believe. It is not a LOTUS design. (Originally, there were two Lotus Mk. 62 built, and they both had transversely mounted engines. One of the was restored a few years ago by BSS for a guy in California. However, BSS were selling a replica of the car called the 62S.)

Making sense of the numbers (and VIN plates)

1

The 50 series are Elites not Eclats

520 was the base model with steel wheels, smaller brakes and the 4 speed Capri gearbox.
521 was 5 speed
522 was 5 speed with aircon
523 was auto

2

You mentioned there were only a few LHD 523's built. Anyone have a firm method for telling if this is truly a factory installed automatic as opposed to someones 'improvement'?

Write to LOTUS and ask for origin of the VIN. Tranny will be a BW. If badged, car is a "524." Get under, check the diff, 4.11:1 on the 'matics. You can chock one wheel, trans in neutral, and turn other wheel and count drive shaft revs. Don't know if this holds for Eclat 524, but on the Elite 504 a power antenna was fitted.

A Federal VIN will be:
SCC - Lotus
B - Eclat
A - S1
B - S2
C - S3
1 - 521
2 - 522
3 - 523
4 - 524
5 - 521 PAS
6 - 521 Auto
7 - 521 PAS Auto
8 - 522 Auto

Yes folks, they *did* make autos that weren't 524s! This info comes out of my Excel shop manual, but as the Excel carries on the Eclat serial numbers I thinks it's good.

(In reply)

I think I'm going to have to disagree with this. Not to confuse the issue, but any Federal Elite/Eclat, and particularly up to '79, only had a 9 digit VIN number. US cars follow rules dictated by the DOT and NHTSA. The very few 1980 series 1 models also follow the old format. The USA, for better or worse, follows a different set of rules than the rest of the world. (Pedant mode=On.)

From the parts manual, page 3:
"Up until 1980, the method of identifying a vehicle is by the use of the Vehicle Chassis (Unit) Number which is stamped on a plate fixed to the right hand wheel arch in the engine compartment. (There is also a plate visible through the windshield on the lower left corner.)

This number is coded as follows:- example 73101234A
73=Year
10=Month
1234=Chassis Number

Elite A=Domestic
B=Federal. (before intro of K&L) & Japan
C=R.O.W
K=Federal 49 States & Canada
L=California. ECLAT AD Domestic
E=Federal. (before intro of P&U) & Japan
F=R.O.W
P=Federal 49 States & Canada
U=California.

There are two variations of the VIN, one for the USA (and some 1980 domestic & ROW) and one for UK and Rest of World, the 17+ charactors being coded as follows:" (I'm not typing all that.) (pedant mode=Off.)

The Excel, while superior in all respects, was unfortunately never Federalised. The data below is correct, but not for any USA Elite/Eclat models.

(In reply to the reply!)

OK then, It's also coded into the engine number.
The number will be in the form D (C) 907 76 06 12844 The 907 is engine type obviously, 76 is the year, 06 the month and 12844 the serial number. The first 1 or 2 letters give the options:
Single letter:
D - Domestic Std D cams 1974
G - Domestic A/C D cams 1974
J - Domestic A/C & PAS D cams 1974

F - Federal Std C cams 1974
I - Federal A/C C cams 1974
K - Federal A/C & PAS C cams 1974

X - Domestic Std C cams 1975
W - Domestic A/C C cams 1975
Y - Domestic PAS C cams 1975
L - Domestic A/C & PAS C cams 1975
AML - Domestic Auto, A/C & PAS C cams 1975 What does AML mean?

P - Federal Std C cams 1975
N - Federal A/C C cams 1975
N - Federal PAS C cams 1975
M - Federal A/C & PAS C cams 1975

2 prefix letters - first letter:
D=1976-1980 European E cams
B=1976-79 California 1976-77 49-state C cams
G=49-state introduced 1978 C cams
K=California 1980- C cams

2nd letter:
C - Standard
D - A/C
Z - PAS
L - A/C + PAS
R - Auto
S - Auto & A/C
T - Auto & PAS
M - Auto, A/C & PAS

If the engine number is 912 instead of 907 you've got a 2.2 litre, but I don't know if they ever got to the USA.

VIN Plate number decoding

I also found the engine number DO 7761113265

So your engine is 907 engine (first '7'), made in 11/76 ('7611' - it's in reverse) and is no. 13265 ('13625')

And the unit number TYRF76

Ah no - that's TYPE 76 - the identity number of the model type (Elites are type 75)

There also standing LOTUS NORWICH ENGLAND

Yup - that's where Lotus are !

VIN Plate number decoding (2)

Now my questions: The car is a: Lotus Eclat 521 type 76

That means you've got a car with a 5 speed gearbox, wider wheels and a radio.
The codes are :
520 - basic model, 4 speed gearbox, smaller wheels
521 - 5 speed gearbox, wider wheels and a radio
522 - 521 with air conditioning
523 - 522 with power steering
524 - automatic transmision
There were also the Sprint 520 and 521 that were cosmetically different - the Sprint 521 also had a lower axle ratio. Addiotionally you can get an Eclat Riviera - slightly diffeent styling and a removable sunroof.

Your car weighs 1100 Kg (2420 lb) and 1519 were built - it's run ended in 1982. It has a 4 valves-per-cylinder dual overhead cam 1973cc engine with 160 bhp at 6200 rpm. It has independent front and rear suspension, a top speed of 208 km/h (129 mph) and 0-96 km/h (60 mph) in 7.9 seconds

There is another version of 'our' car - its called a Lotus Elite Type 75 (there was also an Elite Type 14 which is much older and completely different)- almost identical to the Eclat, except it's rear end is styled differently.

The is a plate under the hood that has the following number: 77/010125F

The 77 is the year - 1977. 01 is the month it was built - January and it was chassis number 0125. The 'F' means it WASN'T built in the U.K., the States, Canada or Japan - it means 'Rest of the World' If you can find the engine number, I can translate that for you as well.

On the back is a sign with: world champion car 1973. Can you tell me what all this means ?

Lotus were successful in F1 at that time and so put "Champions 1973" on to all their cars - in the same was that Ferrari could put "Champions 2001" on to their cars today.

Engine numbers

The engine number is stamped on the right rear of the cylinder block, above the starter motor, and is duplicated on the vehicle identification plate fited to either the left or right inner wheelarch under the bonnet.

" In this case it's only the one on the engine that counts!

IIRC, the block only carries the serial number, whereas the plate and the logbook give the territory, anciliaries fitted, year and month as well. As I said before, a Riviera should be just above the 20000 mark, because my September 1983 Excel has engine 20825 which was actually assembled in May 1983. Sales in 1981-83 of Eclat and Esprit only come to a few hundred, so your car _should_ be a a few hundred lower than mine.

The full number should be something like

DZ 912 8305 20825 where:
D + 912=Elite/Eclat/Excel - UK market
Z=PAS (see table below)
8305=year & month of build
20825=serial number (which includes all 907/910/912, including the J-H!)

The second letter indicates anciliaries:
C=standard
D=A/C
Z=PAS
L=A/C + PAS
R=auto
S=Auto + A/C
T=Auto + PAS
M=Auto + A/C + PAS

This table does _not_ apply to Esprits nor Excel SE, nor the 2.0 cars!

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