R2D2

Hitec Motorsport in Cradely Heath have just doen 2-3 jobs for me and are very good.

I run my Twin Cam on Valvoline Racing 20/50 and have done for some time and have never had any problems.

I use a 186 x 60x 13 with Clamshells and have never had a problem with clearance between the wing and tyre. If you have a standard profile 185s then the diameter will be about 75mm more than using a 60 profile. A 185 x 70 will be about 1.5" bigger diameter. It may also be that you have wheels with too much offset. Do you know the ET or backspace measurement of the wheel?

Looked at their website and I think that the science is suspect. It claims to fill the metal 'pores' with a new compound that is formed by a chemical reaction with the surface of the metal. Just more snake oil, I would buy good oil and leave the additives alone.

The value of the Twin Cam really depends on which one you have and its basic condition. If the engine turns over freely by hand but needs a re-build I would guess the value would be £650 ish for Stromberg carbed engine. £850 ish for a standard Weber carbed engine £1000 ish for a "Big Valve" 130 engine. Let me know what it is as I may know someone who is interetsted.

Most mag alloys are precipitation hardened which means they have been carefully heat treated after they have been cast. Heating them up to 250 degC to powder coat may affect their mechanical properties, (depending on the alloy). I know they will only be at temperature for a short time so any change would be small but painting would minimise any risk.

Don't X-Ray them unless you are looking for porosity. X rays won't find the small surface cracks that are the real problem and will lead to a fatigue failure. The dye penetrants that are commonly available from RS aren't too bad but they are not as revealing as some of the dyes used by commercial test houses.

Bodycote, they have several good quality labs around the country and tend to be CAA and FAA Approved.

I do have an "English" axle casing with new Sierra Calipers and soild rear discs fitted complete with all of the handbrake linkages, which I don't need. I want to keep the diff which is a 4.9:1 and the halfshafts. It isn't set up for a Seven but I could weld on brackets if needed.

Elie, Yes that's right. We also bought a plate type LSD with large 'Atlas' size splines and it has been very successful.

Welding cast iron is very tricky and not a good idea.

The Physics that everyone seems to be arguing about is only valid to describe the Limiting Friction condition and is based on a block of wood sliding along a plank. It is only the friction needed to cause the block to slide. As a tyre is always slipping relative to the road at the point of maximum grip I don't think limit friction conditions models are entirely valid. A chap called Amhurst Villiers described the basic manner in which tyres gripped in the 1920's or 30's and this inolved some means of estimating the mechanical grip as well as friction. This is the same Villiers that worked on the Blower Bentleys and ended up at NASA. There must be some record of the papers that he published

Elie, I used a Quaife conversion on an RS2000 in 2002 and broke 3 half-shafts on tarmac rallies using 185x70x13 Yoko's. I replaced the Quaife units with a conversion I bought from Rally & Competition Equipment which has stood up to more abuse and is a bit cheaper. The price of the conversion is about £1100 + VAT including hubs, shafts, LSD bolts etc.

In general terms it seems to me that the entire situation with regard to roll cages has become a bit confused or may be I just don't understand. I don't think that cars used on non-FIA events need to have FIA homologated roll cages. I have been competing on the MSA Historic Stage Rally Championship for the last couple of years and our car doesn't have any FIA marking and we don't have a Roll Cage Certificate. We have never had any problems at scrutineering or with obtaining an MSA Log Book. I think that if you want to compete in FIA Approved events you need an Homologated Cage which must be marked according to Appendix J of the Yellow Book and be accompanied by a valid Roll Cage certificate. I think that this means that not all cages are homologated and that for National competitions this is not an essential requirement unless specified for a particluar class or event. Does anyone know the definitive situation. I also beleiev that the MSA have just insisted that any new Roll Cages that are designed and require homologation must be tested or examined by MIRA and I guess taht this will add a considerable amount to the cost.

You can find that "Tuftriding" a crank can allow some movement to take place but this is less likley to happen on a used crank. I have tuftrided more than 10 crossflow cranks over the years and never had one move but it can happen. If the movement is small most good engine builders can straighten them out and it is worth checking the run out with a dial gauge before you bolt up the mains.

How about Teflon "buttons" instead of circlips. I have used buttons on Imp engines for years as they are prone to breaking circlips at very high revs and the pin then does a great jog of machining the liner. I have never had a problem with Teflon inserts to hold the pin.

Polyester will be a fairly thick coating compared to nylon and not quite as strong, so I think it is better to try to find a specialist who will apply nylon. I have had all of the wishbones, ARB, A frame and other parts coated in "Rilsan" about three years ago and they are still in perfect condition. Nylon is resistant to petrol, oil and brake fluid. The thickness on a windscreen surround will only be a couple of thou (The heat capacity of the component affects the thickness of the coating that be applied) and it should be strong enough not to be damaged by bolts but putting a flat washer under the head should stop the problem.

A correctly set up LSD should stop the tail from kicking out when you make an abrupt "confidence" lift half way through a bend. If a diff is set to almost lock you could suffer a little more understeer but I wouldn't describe that characteristic as dangerous.

Current "FIA" spec. 1600 cc Twin Cams are producing about 175 BHP these days and they are tested on correctly calibrated dynos. These engines seem to be quite reliable and Lotus Cortinas seem to be winning Historic Sallon races all aover Europe. Several engines of this spec. are also being used in Lotus Cortinas in the MSA Historic Stage Rally Championship and are holding together. My "laughable" 165 BHP enine is in fact a hybrid. It uses a suitably decked 711 block with a small spacer between the front timing cover and the head. This is a well known mod. The engine is 1700cc, all steel has a big valve head, forged pistons, 45s and L14 Cams and was built by Nick Stagg Engineering. I am confident that the power output shown on the dyno sheet is accurate.

Superseven, The original Twin Cam in the Series 1 Lotus Elan and the Pre-airflow lotus Cortina were, I think, introduced with 105BHP claimed. This engine had a cam cover with LOTUS on each sidebar. Early cam covers were plain aluminium in the Cortina and hammerite blue in Elans. Soon after the intorduction a Special Equipment or SE engine was produced and the claim was for 118bhp. I think cam covers were painted green. The power increase was mainly due to a cam change. The Mk 2 Lotus Cortina, later series Elans and certainly the Escorts had an engine which was claimed to be 108BHP and is sometime known as a Mk2. think the only visible difference is in the webbing around the inlet ports but I am not 100% sure. Miles Wilikins book has accurate information. This engine had Lotus on the front bar. The Stromberg carburettored cars had a slightly different cam cover with a lug cast in for a throttle cable bracket. This later engine was also available as an SE and again claimed 118BHP. The intorduction of the Elan Sprint 130 saw the Big Valve engine start production. From memory the valve sizes were increased by 1/16" (1.5mm) diameter on the inlet with no change on the exhaust. I also think this engine had SE cams. The cam cover on this engine had LOTUS on the front bar, had ribbed side bars and "BIG VALVE" cast into the cover. Claimed power was 126BHP This engine was also fitted to the Elan +2 130 and the 130/5 with 5 speed Maxi based gearbox. It really isn't a great box. I would sell it some one restoring a +2 and fit a T9 or similar. It was also fitted to Europas but the head casting is slightly different. The "130" engine also saw a change to the 701M Block which had much better main bearing caps and more internal stiffening than the earlier engine but it was still 1558cc. Your comments about Brake Horsepower are fairly easy to explain: Torque, horsepower and bhp are three terms used when measuring the power of an engine but where did they come from and how are they worked out James Watt wanted to prove that his steam engines were better than his competitors and he needed a rating system. Because most steam engines were being used to replace the work horses did, he decided to call the new rating 'horsepower'. Tests done during the time worked out that one horse would take a minute to lift a 1lb weight by 33,000 feet. So, horsepower is the amount of work done in a stated period of time. Horsepower = (torque x rpm) / 5252 Torque = (horsepower x 5252) / rpm So, for example a modified Zetec may put out 190bhp at 6000rpm. To work out the torque: Torque = (190 x 5252)/6000 = 166.313lbf.ft Therefore Horsepower = (166.313 x 6000) / 5252 = 190 5252 is used to convert the distance used to lift the 1lb weight into revolutions per minute. Lets say for example we have a flywheel which is two feet in diameter (one foot radius) and a weight of one pound. It'll take an engine which develops 1 lbf.ft of torque to lift it. To calculate the engines horsepower, you need to work out how many times a 33,000 foot rope can be wrapped around the two foot diameter flywheel. Circumference of a circle = diameter(in feet) x pi. Therefore Circumference = 2 x 3.1416 - 6.2832 feet. So, the original formula for calculating horsepower is Horsepower = (torque x 6.2832 x rpm) / 33000 Seeing as one horsepower will always move the one pound weight 33,000 feet per minute, and that the flywheel used in the horsepower calculation will always be two feet in diameter, we can divide both parts of the formula by 6.2832 to simplify it. So, 33000 divided by 6.2832 is 5252. Where did the 'Brake' come from ? Measuring the output from an engine can be done in a couple of ways. 1. Put the engine in a car, and measure the performance with a stopwatch. This is pretty hit and miss, because you have to take into account loss of power through the drivetrain but it could be estimated from roll down values. 2. Drive the engine against a brake to measure it accurately. The barke is used to absorb the power produced by the engine. Take the two foot diameter flyweel and engine in the previous example, and put a leather belt over it. At one end, put a 100lb weight, and at the other, a spring balance. When the engine is not running, the spring balance will read the weight, 100lb. Start the engine, and the reading on the spring balance will fall by whatever amount of torque the engine produces. Say it produces 60 lbf.ft of torque, then the reading will be 40. This reading can be used to work out the bhp using the formula Horsepower = (torque x rpm) / 5252 Edited by - Chris Flavell on 12 Dec 2003 07:18:48

Twin cams have always been much maligned but if they are properly built and maintained they are quite reliable. When they first appeared in 1963 they were quite sharp in terms of power output and they didn't lose their competitive edge in rally Escorts until about 1970. Quite a good track record really. The number of races and rallies that they won around the world was quite incredible at the time. I agree that time has passed it by a little but the one I have in my Seven produced 165 BHP at 7500rpm, when it was freshly built and has run faultlessly for the last few years.

If the "LOTUS" name is on the front of the cam cover it is likely that you have an "Escort" generation of engine, which I think were nominally 108BHP. I think that the 95 BHP remarks were for the early engines built at either JAP or Villiers in Wolverhampton. The later engines were much better and did tend to develop the claimed outputs. I can't think why re-jetting a standard engine would help to improve power very much as by this stage of its development the engine was fairly well sorted. The K & N's may make a very small improvement but not too significant.

I use a PC680 with a 1700 Twin Cam fitted with a geared Hi-Torque Starter

Nick Stagg Engineering just outside Bristol is first class.

The output shaft of the gearbox has a male spline on the end of the shaft. I think that the spline length is about 2 inches. The spline is normally a larger diameter than the output shaft. The female spline on the prop fits onto the output shaft through an oil seal. If the prop is too long it will probably damage the oil seal in the end of the gearbox tail housing. If it bottoms on the spline it may apply an axial load to the gearbox output shaft and this is not a great idea. I would expect to see about an 1" to 1.5" of the prop "nose" visible outside the tail shaft of the gearbox. Edited by - Chris Flavell on 5 Dec 2003 09:19:07