by Alex
After two hillclimb events in the car with the new engine set-up, we have some work to do to fine tune things.
At a very wet Wiscombe at the end of April, the front engine carb jet dropped out after running really well. It happened quite quickly with little or no poor running beforehand, suggesting that the jet had been adjusted out too far when on the rolling road, and that the needle may be too lean thus requiring artificial enrichment by screwing out the jet.
We rebalanced the carbs and lock-wired everything in place as a temporary measure.
The following weekend at a sunny Werrington the car ran reasonably well but without the sizzle it had before. We then experienced misfire at the start line usually coinciding at the first gear change then clearing. The car revs out to 9k and the misfiring only happened on Jenny’s run after mine as the ‘A’ driver. This suggested that the plugs were fouling up with all the tickover waiting time, so perhaps the needle could be too rich low down. The plugs certainly looked fouled up but it was difficult to tell after a run up and then back down the hill. Changing them certainly helped, as did getting Jenny to rev it like a boy-racer before the start! On further inspection of the old set some of the porcelain had broken down.
Our conclusions are that the needles are too lean at the top and too rich at the bottom, as the plugs seem to be getting too hot and fouling up at the same time. Also, starting requires the choke but the engine will not run at all with it left on and a very light foot is required on the throttle.
We also wondered about dirty fuel, the facet silvertop pump has a poor filter which is easily blocked.
We are using SU needles in Strombergs, so using www.mintylamb.co.uk found a couple of alternatives using their comparison graph. BG which is much leaner low down and richer top looked perfect, but the curve proved too steep at the crucial 3 to 5k rev range, so we have tried CS2 which has the same curve as the CS1’s previously fitted, but richer at the top with a smoother curve.
After road testing and installing a glass filter before the fuel pump we await Wiscombe on the 17th/18th May with baited breath!
