It’s funny how stroppy some people get about Classic cars. We have done a few E Type Jaguars fitted with throttle bodies on a Weber carb manifold. Fuel consumption is about halved and the performance is better right across the rev range simply by having the advantage of mapped ignition. But to many this is nothing short of sacrilege.

I can appreciate that some people want the original driving experience of a car that is exactly how it left the factory in the sixties but you soon find that the traffic and roads are nothing like they were in the sixties…trust me I was there and I know. So what you could live with back then on a Sunday afternoon drive just doesn’t stack up when faced with the current levels of congestion, not to mention that fuel back then was five shillings a gallon which equates to a little over 5p per litre -  that bit of the sixties I would not mind seeing again!

The E Type shown here (you may have seen it in a previous issue) has not been desecrated with throttle bodies – it has been blessed with a supercharger. Malcolm Stevenson has fitted a Rotrex blower to the E Type that he has owned for over 40 years; in fact he has done the job twice because the first Rotrex proved to be too small for the job and only delivered about 5 psi of boost. With the new supercharger unit the engine was delivering 390 bhp and if you consider that the original engine made about 225 bhp (250 bhp was the inflated claim in the sixties) that’s an awful lot of power.  Enough in fact for Malcolm to win fastest E Type again at the one and only annual event that he competes in. Last year he beat a full race E Type on triple Webers and this year he beat a very expensive lightweight aerodynamic E Type. A point to note; when people spend the right sort of money (usually around £100,000 plus) it’s called a “re-creation” - it’s not a replica or a copy of the original.

Malcolm’s E Type has full road running gear and crossed the timing lights at a decimal place short of 170mph. Now he has been back on the rollers with forged pistons plus revised cam timing and the engine showed 420 bhp with the injectors on 100%. He will be back when we get in the bigger injectors and next year he is aiming for over 170 mph. Not bad for a 50 year old car.

Capri V6

Capri owners tend to be a bit more down to earth with what they spend on their cars and fitting a non-standard engine isn’t frowned upon too often. The one in the pictures was a 2.8 injection special back in the day and, like the E Type above, once had a supercharger fitted. It was, apparently, a bit temperamental so the two valve motor was replaced with an aspirated Cosworth 24v V6. I see a lot of these engines; not the most powerful in the world but super-smooth and over 200 bhp out of the box. If you had the original two-valve V6 you need to do a lot to get near that sort of power.

TDC

I have had a very nice letter from a Mr M.S.Hassell from Falmouth who had been reading my book on Engine management. In his letter he gave me a description of a TDC finder that he made some years back and thought it might be useful for anyone timing cams or setting up the zero on ignition timing.

I generally use a dial gauge as most engines now have a central (vertical) plug hole. But several engines I see, like the LS V8 Series, still have side mounted plugs and a dial gauge is useless in that situation. The LS that I was mapping was a 7.0 litre job and had been mapped previously by an expensive operation that boasted tiled workshop floors and swanky décor with prices to match.

I had the car in because the fuel consumption was dire and the light throttle running was really rough. Most people assume straight away that the mixture had been set too rich but that is not always the case. With any engine sporting a plenum intake and an aggressive cam you will always get a rough idle and some “jerk” when driving on light throttle.

The first thing I do with any car is go over the maps looking for what I call nonsense. You can often spot where the mapper has done a bit here and a bit there and then given up. The numbers just jump at you off the screen. This one was okay apart from the ignition map. Looking at the numbers I was guessing that the operator of the dyno had done full throttle and not much else. Also the numbers made no sense; it was showing far too much advance in my opinion and I base that on having done a lot of these engines in the past.

Getting back to the plot I needed to find an accurate TDC mark. The engine had an aftermarket 36-1 trigger wheel so the reference could have been anywhere within 360 degrees. Access is really tight on this engine in an RX7 so a dial gauge was out of the question, especially so when you look at the plug angle in the head.

I decided to spend half an hour making Mr Hassell’s TDC finder but a slightly modified version. Mr H showed an old spark plug with a nylon rod sticking out the top, smallest possible hole and a tapered section for the bubble to form. You screw in the device, put some soapy water on top of the rod and turn the engine over. A bubble forms, then breaks and re-forms until you reach TDC. By rocking the engine over TDC you get the bubble at the largest point and that’s it; job done.

For my device I replaced the rod with a flexible tube and put a bubble forming section at the top. I cut a short plug thread section and glued in the flexible pipe to make a seal. Now I can hold the bubble upright while the adapter is screwed into the angled plug hole. As our John here put it: “It’s a bubbly tool to have”.  It worked too! I was amazed how easy it is to find TDC once the piston is close to the top on compression. My Mk 2 version now has a rubber O-Ring seal in a groove as the thing leaked slightly the first time I used it.

Having established TDC accurately I put some marks on the crank and checked the timing with a light. The ropey idle was down to having the ignition running 27 degrees retarded past TDC!   Looking at the numbers in the map it had been running a true 10 degrees BTDC on cruise condition so no wonder the fuel consumption was poor. It also shows that the previous expert had not bothered with the timing on light throttle; otherwise he would have been mapping something like 65 degrees to get the power optimised – telling you that the reference is obviously wrong.

The end result is a car that now idles and drives 100% better and I have a really tricky TDC finder in my box for future engines with angled spark plug holes.