[Spridgets] Rejetting carbs for high altitude

[WeslakeMonza1330 at aol.com]

How rich is too rich and what was the HCo (?) reading when set up on the  
dyno?  
 
I know jets aren't cheap but neither is dyno time  so I'd drop the  mains 
down one size at at time test and repeat.  With the idles it's harder  to say but 
again one size at a time.  I'd leave the air correctors alone as  I'd expect 
the enrichment curve requirement is the same but starting from a  different 
point.
 
I see Ron has said to change the timing and fit a softer plug.  I  definitely 
don't see a reason to fit softer/warmer plugs and most definitely  knot 2 
grades.  I don't see a reason why the timing ought to change but  it's not 
something I'd mess with.
 
Weslake-Monza 1330
 
 
In a message dated 23/03/2009 14:33:40 GMT Standard Time, breton48 at live.com  
writes:

This is  LBC but not Spridget content. I hope some kind soul here will answer
with  the right kind of information - no one did on the Lotus 7 list I belong
to.  Below is the message I sent:

Hi... I have a lotus Seven S4 Twin cam,  which was jetted on a dyno at sea
level three years ago. I now live at 7400  feet, and all my driving is done
above 6000 feet. The engine is running too  rich. Any suggestion for
rejetting and should I retard the  timing?

Here is what I have now:

1970 Lotus Seven S4 Twin Cam,  1558 cc  (+20 thou overbore), compression
10:1. 
Twin Weber   DCOE  31 carburetors.  Chokes: 32 mm

Cyl 1    Cyl 2    Cyl 3     Cyl 4     Standard Twin Cam SE
specification
Emulsion  Tube    F11    F11    F11    F11   F11
Main Jet     115    115    125     120
115
Idle Jet        45F8    45F8   45F8    45F8
50F8
Air corrector    155   155    155    155           150

Timing: 25 degrees at idling, 35 degrees at  4000 to 4500 rpm

JLC in the Black Forest, CO.