The cylinder head flow data arrived from Kibblewhite. This last intake tract test they made was on a head with 2mm larger intake valves, porting, a hogged out Triumph manifold, 39mm Keihin flat slide carbs, and oiled foam pod filters. The setup flowed around 212 cfm at 28 inches. Bigger carbs and a pleated oil gauze filter was recommended by Kibblewhite.
The bigger carb and filter idea sounded good. How to do it was confusing. A conversation in Sacramento with the tuner for the factory Triumph mile bikes gave me the answer. He had a set of 45mm Mikuni's with big K and N filters. I bought a pair and they were installed with a hogged out Triumph Performance manifolds. This does the job. Flow with the same valves and ports goes up to 230 cfm, an 8.5 % increase. The basic horsepower formula says: 0.26 x 230 x 2 x 0.9 x .86 = = 92 hp at the rear wheel at B'ville. This is not enough to get me a record. It will be good for over 150 mph with a streetable motor running on unleaded with a muffler, which is a long term goal.
The valves in a Cosworth design are at the corners of the combustion chamber. Larger valves and seats require metal removal from the periphery of the chamber and this dramatically drops compression. A tuner needs to be aware of this and increase valve sizes just enough to do the job and no more. The intakes had larger seats installed and a 2mm increase in diameter. The exhausts were enlarged 1mm and the stock seats reworked to give better flow. This increased flow between 2 and 16 percent depending on valve lift. The desired exhaust flow is between 80 and 90 percent of intake flow. That target was hit. The intakes and exhausts flow the same at low lifts near 1/8 inches. This is not uncommon and no need to worry according to the expert at Kibblewhite. This cylinder head is the best it can be.
The K and N sock was used over the filter during the flow tests. It was on the filter when I sent it to him and I asked him if it is a good idea. He said yes. The sock is a good thing when considering the racing environment.