[TR] Fw: zenith or su's ?

Wayne Lee wayne at motorcarriage.com
Wed Dec 2 13:37:27 MST 2009


Again, I didn't clean up the bottom, didn't go through at 2:38


From: Wayne Lee
Sent: Friday, January 01, 2010 2:38 PM
To: Anthony Rhodes ; Triumph List
Subject: Re: [TR] zenith or su's ?


Hi Tony,
   You gauge the Spring Type by Wire Gauge or diameter in .000" and how fine
they are coiled.
I have a book specifying the differences but they are visibly noticeable.

  I have a Flow Bench and it's of no use for figuring Carb Air Flow(at least
no more than a Shop Vac would be) as the Heads are
 always worked on with none of the reciprocating Valve Train to simulate
actual running.

 Dividing a Cylinder Heads Flow from 2 Carbs to 3 Carbs of the same diameter=
less flow per Carb.
A simple Synchrometer test will verify this.
Cheers,
Wayne




From: Anthony Rhodes
Sent: Wednesday, December 02, 2009 2:26 PM
To: Wayne Lee ; Triumph List
Subject: Re: [TR] zenith or su's ?


Wayne,

I totally agree.  With few spring selections, probably there is only one
spring that makes sense.  But how do you know that the springs in those old
SU's are 1) the original type, and b) still have their original "springiness"?
You would have to measure their spring rate.  Not a difficult proposition.

The case I had in mind when I was saying that maybe someone would need to
change springs is in the 3-carb conversion.  I think it is quite likely (and
probably necessary) if you are going to have any real increase in breathing,
that you would need springs with about 2/3'rds the spring rate.  You would
need a greater spring rate than that if you develop more HP in a modified
engine.  I.E.  I'd guess that if you had a 50% increase in HP, then that would
bring you back to the original springs.

As I said before, there are enough variables that it is a little difficult to
predict, and you might need to verify the actual amount of lift at full engine
breathing.  I presume that people can predict the flow based on displacement,
compression ratio, HP and RPM.  Then a flow bench could verify the actual
lift.  A dyno might be easier to find.

-Tony


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