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It’s no secret that carburettors mix air and fuel in a nicely atomised way before the hungry engine sucks it into the cylinder, compresses it, ignites it, disposes of the hot gases and then goes looking for more to do it all again. Dick had a look over my maths and, at 6000 rpm, each cylinder does all of the above about 50 times every second.

And while it is feasible to compress the charge and ignite it with a wide range of air/fuel mixtures, there is an optimum range where the presence of sufficient fuel helps control the unreasonably high temperatures within the combustion chamber. If the temperatures are allowed to get too hot, bits can melt, and that is not a good idea.

So, as part of the process of preparing the Dick Jones Special for racing, I’m paying closer attention to just what is happening within the fuel system. Let’s start with fuel pressure. It’s quite easy to check. Simply disconnect the fuel hose from the carburettor, hook it up to a pressure guage, and switch on the pumps. Holleys like about 6 psi, Webers about 1.5 to 2 psi. If you don’t have enough pressure, then during a part of the lap where g force is present, the fuel can be forced to the side of the float chamber, lift the floats and thus cut off supply, even though the level in the float chamber is below the target. Result: less fuel than required in the system when you point the big toe again.

Next is fuel flow, which is the volume of fuel that can be delivered by the pumps. Holley says a good formula is a pound of fuel per hour per two horsepower. So if you have 300 horsepower, the pumps need to be able to deliver 150 pounds of fuel in an hour, which is 2.5 pounds per minute. As a rule, an imperial gallon of avgas should weigh in at about 7 pounds or so, and an imperial gallon is equivalent to 4.5 litres. Be careful with US based literature here, because a US gallon is only 6lbs. How do you check it ? I started by buying a measuring jug with fine scale gradations, and using a stop watch, pumped fuel into the jug for exactly sixty seconds. It’s worth taking care here to measure the flow from as close to the carburettor as possible. That way, you know you’re replicating what is probably happening when the car is running.

In my case, the pump delivered 2.24 litres a minute. That equates to 30 gallons per hour, or 210 lbs per hour, which is more than enough.

Now for the carburettor. Assuming there are no leaks, and I’m including air and vacuum leaks here, the common approach for my old Holley is to allow a measured amount of fuel into the engine through a main jet. Actually, there are four of them, two for the primary system, and two for the secondary system. These jets, conveniently enough, have numbers stamped onto them which indicate the diameter of the hole in each jet, measured in thousandths of an inch. If you refer to the Holley website, you’ll find the standard jet sizes for your carburettor, but… a racing engine is a bit of a throughbred, with optimised flow characteristics into and out of the combustion chamber, higher compression, and so standard settings might be best viewed as minima. The point of these optimised flow characteristics is for as much fuel and air to get into the cylinder as possible in the short time allowed, and then for it to leave as quickly as possble once we’ve burnt it. The potential problem here is that the fuel itself, before it is ignited, has a nice habit of cooling things down just a tad before the ignition lights it up, so it seems sensible to fatten the fuel/air ratio up as we improve the flow in and out of the cylinder. This is where going for a bigger main jet can help.

Next is the air itself. We’ve all noticed how much better our cars go at night, when the air is colder. The reason is that cold air is denser than hot air. I have read that dropping the air temperature by 1 degree Celsius can add 1% more horsepower. True or not, cold air certainly has an impact on horsepower, but temperature is not the only indicator of a change in air density. Altitude has an impact, since air gets thinner, the higher we go. And the general weather pattern is the final influence on air density. If we are currently with a weather pattern where there is a Low overhead, then the air is less dense than it would be in the middle of a High. That is why the top drag race teams consult weather stations as they prepare for their runs down the quarter mile. If they set up for low density, and it’s high, they run the risk of leaning things out too far. So while intercoolers and cold air boxes all help, there is definitely a correlation between increasing air density and making an adjustment to the ratio of fuel.

It’s a pretty simple task to replace the main jets in a Holley, and they are available in a wide range of sizes. Make a note of the change you made, run the car, and look for a change in the colour of the plugs, the tailpipe, and maybe a bit of black smoke when you floor it. The experts I’ve spoken to suggest that you finally jet for performance, and that’s mostly a subjective thing. If you feel as though the car is better, then it probably is. But if you feel as though it’s still not right a few days later when you get to the track, remember that the air is, more than likely, different.

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The Historic Racing Club, ably assisted by the Alfa Romeo chaps, took on the big guys with the 2006 Ice Breaker meeting, and they did a superb job. There were over 255 drivers, all praying to the weather gods. The met guys promised a mostly fine weekend, and it was…mostly fine.

The Historic field was one of the largest we’ve seen for a long time with over 30 cars. Now it’s fair to say that Rodin Wootton is his Brabham, and Ken Williams in supercharged BBM Mercedes, were always in the running for the chocolate fish. Formula Fords were well represented with some immaculate cars and, if past history was anything to go by, they were always going to be the hungry pack hard on the heels of Rodin and Ken, and you can never discount John Holdsworth in the Merlyn Mk10.

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Where exactly the Dick Jones Special would feature in the field, I wasn’t sure. This was only the second time I’d raced with a lot of these cars, and it has been a very long time since I last drove the Dick Jones Special with gusto on a dry Pukekohe. What concerned me most was being in traffic, because that is a new thing for me.

My racing days in Formula Ford (Class 2) were in a small group in relative safety at the back of the pack and, although I trust the Dick Jones Special’s handling abilities, some of those single seaters are hard to spot in the mirrors and a lot more nimble.

Practice was late in the morning on a track that was still a little cold and slippery but I entered into the spirit of things and set out to do my best. Oh how quickly it all vanishes from your mind when corners arrive much faster than they have before, and your brain (well, my brain at least) loses touch with how many gears you have, where they are exactly, and what order one is supposed to use them in. The car was squirming under brakes, understeering around Railway, and I am certain that someone has changed the shape of the hairpin over winter. It was not pretty, and even though I remembered to check temps and pressures, and qualified second, somehow I knew that school was just beginning.

To Race 1, where a brand new experience lurked on the front row. I have never been on the front row. Rodin is behind me in my blindspot, and on Grid 4 is Graeme Andrews in his super quick Titan, half a second off my qualifying pace.

One thing the Dick Jones Special is not good at, is starting off the line. The open diff is quite prepared to let go and I have sat there in the past changing gears and going nowhere. I opted for a few revs, judicious clutch, and pointing the big toe once things were rolling. By the first turn Rodin was in front. By the second turn, Graeme was in front as well, and it was time to accept the fact that we were there to race, and get on with it. Out of Railway I went for 6000rpm, grabbed top, and set off.

As Ken and Rodin disappeared into the distance, I was left to the next few laps of attempting to keep it tidy, establish just how much grip there was, and get braver. But everytime I got to Railway, Graeme Andrews was in my mirrors again.

The flag marshals were keeping a close eye on things with white flags as we stormed down to the tail enders, and blue flags as we rolled past. Thanks guys (and girls). By the time the flag fell I’d managed to stay in third place, but Graeme had put in a blistering lap somewhere which saw him sneak though to Grid 3 for Race 2 on Sunday morning.

Nonetheless, the best lap was recorded at 1.10.48 which is the best ever for the Dick Jones Special, and a personal best for me. (See the latest video for that lap).

The weather was a bit damp as formed up the next morning. The flag fell and we set off quite cautiously. Lyall Zohs got through off the start, but I managed to get past him and Graeme up towards the kink along the back straight, and closed in a little on Ken and Rodin at the hairpin. Into the Jennian Homes sweeper, and double yellows were waving because of one of the Fords had spun across the track and the driver was desperately trying to push his car clear of the traffic. We slowed and were then met with red flags after Railway. Back to the grid to sort things out, and wait for the restart.

The weather gods looked down and realised their mistake, so the sun came out and began drying the track.

We set off again and thankfully there were no further offs. The Dick Jones Special was very strong, and grip was improving lap by lap. Ken and Rodin were still in sight when Ken had to pull out with a broken supercharger drive. By race end I was second, 1.76 secs behind Rodin, and very happy.

Race 3 was a handicap, reverse grid with Graeme Andrews and I starting of Grid 30, and Rodin further back along with Stan Benbrook in his immaculate Lynx. This was another steep learning curve for me. To pull up among a tight field of Fords all jockeying for position and try to make the right decision on where I should go to get through, saw me asking the Dick Jones Special to hang on through the outside of corners, or take a faster than I’d thought possible tight line through Jennian Homes. We were making good progress though, and managed to keep moving through the field until the engine fell off song in Lap 4. I slowed and coasted back to the pits. After things had cooled down I pulled the rocker cover off to find seven pushrods where there should be eight.

All in all, the Ice Breaker was a fantastic meeting for the Dick Jones Special. We’ve opened up the valve guides and thrown away the stem seals to encourage oil to get in there and help out. We’ll fatten up the main jets a little more, just to be sure we’re doing everything we can to manage the combustion chamber temperatures, and keep on learning.

As well as that, I hope to soon be able to move the centre mirror a little further aft, which will open up the view behind.

Don’t forget that there will be delayed tv coverage of Sunday’s racing on Sky Sport and Prime very soon.

Time now to get ready for TACCOC’s Spring Classic in Taupo. A new track that many of us have never been on before, and a lot of questions about whether the gearing will be right or wrong. Stay tuned, or better still, come to Taupo and see how we get on. October 7th and 8th.