Owning a Lotus 7 S2

Throttle Linkage Mechanism

admin — Mon, 10 Aug 2009 05:03:40 +0000

We have been a little unhappy with the shallow linkage mechanism which we have used until now. The operation was OK but very much either on or off. We have now reinstalled the original throttle linkage which produces a much smoother action.

Narrow rear wings

admin — Fri, 31 Jul 2009 18:19:23 +0000

For long time we have been contemplating substituting narrow rear wings for the wider Series 2 wings. After having changed to Elan wheels the wider wings looked a bit odd, so we decided to give the narrow wings a try. We sourced new wings from Redline and we are quite happy with the result. The car now looks more beautiful with the rear wing edge flush with the tyres (which we changed to 145/80).

Cheshunt factory

admin — Tue, 14 Apr 2009 15:50:31 +0000

Our 7 was manufactured in the Norwich factory where Elises are done nowadays. However, many (most?) Sevens were produced in the Cheshunt factory in the Great London Area. A visit September 2008 confirmed that the old Lotus buildings are still there. The Lotus main buliding is now a plastics factory and the building where Lotus Components resided is now a fitness center. The buildings as such seem unaltered, even the winch where they lowered the Sevens from the first floor remains, as does the ramp of the Lotus factory (see photos).

Cheshunt factory 2008

Lotus Components (now gym) 2008

Lotus Components ca. 1962

Ramp 2008

Summer outfit

admin — Wed, 30 Jul 2008 17:55:43 +0000

SB2237 equipped with Brooklands (as in the good old days).

2008

1988

Jetting of a single Weber 40DCOE 2

admin — Tue, 22 Apr 2008 16:39:54 +0000

Our Lotus has the basic configuration of a single Weber 40DCOE 2 on a Lotus alloy manifold. The performance of the basic engine is moderate, 66 HP at 4600 rev/min. The ports of our engine have been enlarged and the combustion chamber has been flowed moderately. Also, humps and edges in the inlet manifold have been smoothed out and the exhaust is 4-2-1. But most importantly, the engine is equipped with a fast road A2 cam. With the 0.06″ overbore our data show a power output of some 80 HP at 5200 rpm. Not a high reving engine but an engine with good midrange torque. This power figure has been used for jetting of the Weber extrapolating from the unmodified engine.

Basic 66 HP Modified 80 HP

Camshaft Ford A2

Choke 26 28

Aux. venturi 4.5 4.5

Main jet 115 125

Air jet 165 160

Emulsion tube F16 F16

Idle 45F9 45F9

Pump jet 65 65

With this setup up the car is lively and has no hesitation during acceleration.

Smiths RVI tachometer reconditioning

admin — Tue, 15 Apr 2008 13:59:41 +0000

The aquired RVI tachometer did not work, so a repair was necessary. The circuit board was in a fairly bad shape, but fortunately the board from the aquired RVP meter could be swapped. Apparently, Smiths used the same circuit boards for several models. The two transistors were unidentifiable (not the standard GETs), so they were exchanged with two AC 128 (NTE158 is difficult to source in Europe). The major capacitors and a few resistors were also changed and, voila, a working unit.

A note on bezels. The old, nice full-V bezels are no longer available for 3″ instruments, so care must be taken to save the old one which is not always possible. Apparently, these bezels are avaiable for 2″ and 4″ instruments so maybe there is just so much more demand for 3″. One can only hope that someone starts to produce them again, and this time slotted so assembly is easy.

Odometer repair

admin — Sat, 24 Nov 2007 07:49:57 +0000

When the Smiths 8000 rpm RVI tacho was introduced for the Lotus 7 in 1962, the original speedometer looked a little outdated in comparison. We wanted to find a contemporary matching speedometer and we found one on ebay.

Matching tachometer and speedometer

While this speedometer is basically contemporary Smiths, the dial is probably not (the calibration information is missing). The instrument showed the correct mph, but the odometer counted twice the number of miles. Encouraged by Anthony Rhodes “Repairing Jaeger & Smiths Speedometers” (Google if you want it) we decided to open the box to see if we could mend it. Here we found Anthony Rhodes’ description invaluable when we had to refit the small springs and spacers in the right sequence.

Odometer wheels disassembled

The worm gear (20 teeth) and the drive gear (48 teeth) should give a calibration of 960 revs per mile, but we measured half of that on the odometer. We soon discovered that the outermost wheel (at the arrow on the picture, referred to as the “1/10th wheel” by Rhodes) had two “cogs” insted of one. This in turn caused the “one mile wheel” to turn a digit for every half revolution of the “1/10th wheel”, effectively halfing the calibration. This was corrected by filing off one of the “cogs”. The now 960 rpm calibration is low by 6% which we find acceptable.

Coincidentally, we had another (newer Smiths) speedometer which exhibited exactly the same fault, counting double miles. In this case the cause was a different one. We noticed that the pawl advanced the driving gear by two teeth instead of one, effectively halfing the number of teeth on the gear.

Pawl and odometer driving gear

The pawl movement is accomplished by a worm gear driving an eccentric axle. It was evident that the pawl movement was too large. Hence, we found an axle with less eccentricity which solved the problem.

Axles with different eccentricities.

50 Years of the 7

admin — Tue, 20 Nov 2007 15:27:40 +0000

This september we took our Lotus 7 to the 50 Years Celebration in Norwich. The longest journey we have ever done with it, so we were quite excited to see if we had cured all the minor engine problems, so we could get back safe. To our delight, the car performed excellently, with acceptable oil consumption.

The event itself was a big venture which we enjoyed a lot. The focus of the celebration, the 7, outshone the rather casual planning and made it a memorable tour for us. It was indeed impressive to watch the showground carpark with more than 300 Sevens, Caterhams and Loti.

Showground carpark

The highlight of the event, we think, was the exhibition with Lotus cars from all years, beginning with the Sixes up to the end of production of the Seven in 1973.

Lotus through all years

We also enjoyed the visit to the Lotus factory and the Morning Blat to Sandringham Castle where the picture of our Lotus was taken. It evidently shines among compatriots. A very memorable journey, indeed.

SB2237 shines.