I like this power/torque print out that DBM shared on his stock S40.  It really paints the picture of the big flat torque curve these bikes have.  It may not have a ton of hp and torque, but it's delivering 80%+ maximum torque from about 1800rpm up to about 5500rpm.  To Dave's point, it's nice to be able to hang out in 3rd or 4th gear rather than running up and down through the gear box with the engine screaming between  6k-12k rpms on a short stroker.

Finn, I am also a fan of David Vizard.  His book "How to Port & Flow Test Cylinder Heads" is very informative.    He has a couple of other books that are excellent all around tuning guides.  "How to Build Horsepower" and "Performance with Economy" are good practical roadmaps to improved performance.  The mods he suggests work.  Here are several other books you might find interesting:

Practical Engine Airflow by John Baechtel

Four-Stroke performance Tuning by A. Graham Bell

Harley Davidson Evolution 1340 Performance Tests by Branch Flowmetrics

V-Twin Tuners Handbook Vol 1 thru 4 by D. William Denish

Don't forget YouTube.  In addition to David Vizard's PowerTec, several channels come to mind.  Eric Weingartner has a lot of good instructional vids.  The MBE Group has some good vids as well.   Like all info available on the internet, you have to use your own judgement to determine what might be applicable to your situation and whether or not the info is technically sound.  There's a lot of screwy stuff on YouTube.

The LS cylinder head looks to me like it might lend itself to Vizard's Poly-Quad setup.  The exhaust port sweeps to the right.  That might help generate and maintain the vortex that the design is trying to create.  A few years back I fiddled around with it a bit, but I only had a larger intake valve.  Didn't try enlarging one of the exhaust valves.   Someday I might revisit that setup.  For now, I have my hands full with the 35mm intakes.   Since you have the ability to test at high differential pressure, I suspect you might be able to do a much better evaluation of that Poly-Quad setup.

When you go to Germany to set the Savage Land Speed Record (SLSR), you might wanna make sure you have a stock flywheel installed.  The heavy wheel is good for a little more top end.  

Regarding tank slappers, I've never experienced any head shake on my LS.  The frame is stock, and the forks are not raised.  The only change is the rear shocks are one-inch longer (11.5" vs 10.6").  I think it handles good with that configuration.  It runs straight at high-speed, and the low-speed manners are improved dramatically.  Never had a problem with head shake.

Sorry Dave , 101.1 mph our current SLSR holder !
It also comes with a free target for your back
A goal , a quest , who is next to try ?


Won’t be me ,    , my speedo has auto record so if I beat my last record it holds it automatically, just checked my speedo , an embarrassing 93 mph
But it’s pretty quick gettin there !

All,

I have now got the collection of orifices caracterised relative to each other, so that I can take measurements that span several orifices.
At the moment I am using:
20-50
32-80
48-120
103-206
128-320
Below is a set of curves which are important to me. For one it shows the difference in flow through the exhaust depending on whether I suck or blow through the port. It flows better the way it is intended to.It also shows the relationship Inlet/exhaust, which is also an important parameter in a well balanced engine.
I am happy that I built this bench, because I am starting to know things, instead of just guessing.
I have been promised the calibrated orifice tomorrow, so very exciting to see how far off these curves are, not that it matters since It is the relative progressing numbers that matter.
Cheers, Finn Hammer

All good fun.

Mike,

Yes, when I say "blow" I mean flow in the direction the engine produces during normal operation. I was myself puzzeled by the difference, but am happy I made the comparison, because lazy me wanted to avoid having to reconfigure bench from suck to blow, but now I understand I have to. I have no idea how this difference in flow vs. direction can happen.
I think you are right about how you apply the pressure differential across the port, either way should be fine.
I had the opportunity to compare my orifice plates to the flow through a Helgesen plate manufactured by a toolmaker guy with a lot of experience , and my gear tracks his within 2.5%, I may correct my plates ratings to match his exactly.
I calculated the diameters of my orifices using an Excell spreadsheet, and in this sheet there is a factor called "discharge coefficient" you can set it to whatever you want and this will change the size of the orifice. I set it to 0.62, others have used down to 0.58. Anyway, the resulting orifices show remarkable accuracy, and certainly good to go for comparing progress in the porting process. When we try to compare from your bench to mine, that is when the problems arise, because none of them are presicely spot on.
I really have no idea which port bias to go for, I am shooting for what the valve size/port efficiency dictates. Basically, I will take what I can get.

As promised, here are the curves taken this morning, comparing 15" to 28". I am satisfied that the 1.366 conversion factor between 15" and 28" has been demonstrated. The port pretty much obstructs any further increase in flow from 0.25" valve lift, and up, but this ought to change when I start to open up the port.

Cheers, Finn Hammer

Here is the latest graph.