The in-house Access Norton plot monger just stumbled onto Yves airflow data sheet on the previous page and couldn’t help himself, so fed the Flemish data into the Yankee translator and out came the information below. Let me know if there is an issue or if the translator screwed up again (damn machines are always making mistakes!).
The airflow reported should be sufficient to make ~ 70 crankshaft HP if compression, cam and pipe are optimized.
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Good Morning Together
Yes indeed a very good job. Let me try an interpretation of these graphs related to the power- graphs we have on Page 10:
Graph 1: The green one is from the stock Fullauto head with 38mm intake valves.
Graph 2: The blue one is the one with intake valves of 41mm and just blended ports to the bigger valves. Otherwise the ports are standard
Graph 3: The red one is the one with the bigger intake valves and re- shaped ports.
1.) What strikes me is that graph 2 over a very wide range of valve- opening has the better flow than graph 1, and yet, the power should be down by nearly 8hp (that's 10- 12%)??? I wonder.
2.) The flow of graph one is getting better when the valve is nearly fully open (max. lift of the valve should be 0,425"?). Well, what ever the reason may be for this effect (may be the higher velocity of the incoming charge wins over the bigger intake surface?), the big valve engine won power in the upper rev.- range. According to the flow graphs it should have been just the other way round.
3.) Could is be that the dyno- man mixed up the 2 power graphs? If that's the case I tend to believe his graphs.
Conclusion:
What we are doing here is a kind of a development process. Yves, just run in the engine realy well (1000kms), and then do another test- run on the dyno. If the power graphs are still not satisfactory, we will have to look at the exhaust port as well. Remember we have a system here, consisting of intake and exhaust- valves- and- ports.
A few years back I had a discussion with Roger Titchmarsh (yes, the frame builder). He had just finished a very fast Matchless G 50- Engine for Hugh Anderson who very successfully competed in the Brittish CRMC- Championships at the time. He told me that the shape of the exhaust- port is also very important to the power of the motor.
Or also a few years back, I talked to Stuart Digby very successfull BSA Sidecar- racer. He told me that a real step forward for his Race- BSAs was the opening of the exhaust- valve and the porting.
So, the next step after all this work should be the exhast port as well. Don't under- estimate this detail.
Yves, you are only young and there is still some work to be done.
Did you test- ride your NORTON with the re- shaped ports yet?
All the best to all of you for a happy Easter.
