The head clamps to the top of the column

Here the motors are pulling full tilt on the head, with inlet valves opened 0.4" each. It reaches almost 46" and flows 249CFM.

Wow!  Nice job Finn.  I love the length of the test stand.  Flow should straighten out nicely.  The metal orifice plates should be very accurate.  The manometers are beautiful.  And that vacuum source; speed control, four pumps, 46", what can I say.  You really have taken it to the next level.

Thanks for running a baseline at 15".  Shows my jalopy is probably way off the mark.  I'm very interested to see how the calibration turns out.  

I've been messing around with 35mm valves.  Once I opened up the throats to about 87%, the wall of the seats got very thin.  I am concerned about that.  I use an old junk head that Fast650 sent me.  It's my test mule.  I guess there's only one way to find out if the seats will stay put.  Gotta do the mod to a serviceable head and run it.  Pretty risky but no guts no glory.

This should give you an idea of what the seats looks like after opening up the throats to 87% (that's 1.200").  

Thank you for your kind words, Mike.
I hope to get the calibrated orifice this weekend already. I am in contact with some old guys that are into racing vintage cars, and they know a lot, even to the point where they can have custon cams ground based on their flow measurements. I hope to pick their brains, but of course they are wary of a newcomer.
I find your work with bigger valves interesting. From the curves you show, I get the notion that the bigger valves (which are now relatively closer to each other) start to negate the benefit of size due to mutual shrouding. Since I dont _know_ anything, I have to rely heavily on what I can read and hear. David Vizards book has turned into a bible for me, worth read and reread again. From it I read about PolyQuad configuration of the valves, a big one and a small one of each. This should change the 4 valve heads predominantly tumble style fill of the cylinder towards a swirl style fill, which is allededgedly beneficial for the low end combustion and thus torque. This would probably lead to the same shrouding effects in the high end, but perhaps not low down. Would need to exchange one of the valve seats for a bigger one though.
This work is very interesting, my hope is to get enough power to reach 100Mph without sacrificing the low end. Not that I need it, it is illegel to go that fast here in Denmark, -would have to go to Germany to try it out, and I am not sure I dare to do it either, due to the bike's tendency to go into wobbely oscillations (think it is called tank slappers), hopefully a change of steering stem bearings will help that out. But I think that since the old british singles were able to do the ton, then mine should too. We will see about that.


Cheers, Finn Hammer

Bystander looking at Dave's bike: "how fast is it?"
Dave: "It will do the ton"

Gary_in_NJ wrote on 02/02/24 at 06:47:41:


Yep - That is why I had to find out!

It is far less scary and fun at 60mph!

SpammyToo, All:

Yes, I am shooting for a higher rate of CFM, but also for a higher runner velocity, so perhaps even a smaller runner diameter than stock. A high speed in the inlet runner means that more air will be rammed into the cylinder by the time that the piston is around about bottom dead center, and the inlet valve is already close to shutting, due to the inertia of the air coloumn.
Time will tell since, as I mentioned before, I still _know_ only a little, but have read, heard and, in particular, speculated a lot. Time will tell what I can experience, and thus _know_.
For example, I thought I knew, due to the written wisdom of Orifices, that they can only produce reliable readings at 50% to 90% of their flowrate. My experience now is that this range can safely be extended to 40% to 100%.
What is the point of that, you may ask. For one it means that I can cover the whole antissipated range of flows with just 2 orifice plates, one going from 40CFM to 100CFM, the other from 100CFM to 250CFM. There is no need for overlapping ranges, as I thought before.
I can assure you, that having to change orifices during a measurement session can amount to a big nuisance over time.

I would use a remotely adjustable Iris orifice if I had the means to properly calibrate one, and if they come with a large enough range (can they close down to a small enough hole):

https://continentalfan.com/e-catalog/industrial/dampers-industrial-applicatio...

I am unsure, english not being the first language of mine, if there is some tounge in cheek in your comment about moving a ton of air, but to be clear, the "ton" is a term loosely assigned to large quantities of something, 100 in this case, dealing with speed, in this case miles per hour.

I agree that more contemporary engine designs, with shorter strokes, higher rev ceilings, water cooling, injection etc. are hard to compete with, and we shouldn't. We should not expect such high break horse power numbers, as displayed by these modern marvels of engine technology. KTM are pulling 63 horsepower out of their recent severely oversquare 690cc single, at 11.000 rpm,  so if we shoot at 45 we would be doing very well indeed. We need power to move the thing, but it is the low end grunt that really counts when driveability is concerned.

Meanwhile, let us not forget the wisdom of Carroll Shelby, when he stated that there is "no replacement for displacement", the massive 40 cubic inches being the main reason why I bought this bike in the first place. The low price of it on the used market being the other.

Cheers, Finn Hammer