[Spridgets] Carburetor Gasketing

Robert E. Shlafer pilotrob at webtv.net
Sun Apr 13 09:12:11 MDT 2008


I think there's a reason for those different
recommended needles for the stock engine in the factory manuals or they wouldn't bother listing them? 

(Then again, they're British so maybe they would!. :).

The SU is a "constant VELOCITY" carb.

"Volume" increases as air valve rises
but "density" of air depends upon "density" altitude (pressure altitude corrected for temperature....they haven't found a way to correct for relative humidity far as I know).

So a cubic foot of air at 5.000 feet contains
less "air molecules" than a cubic foot of air
at sea level. 

Layman's terms..."what it all means".......

Here's what Burlen told me: "Weak" needle
is basically for motors run at/over density altitudes of 3.000'.

"Rich" needle for "drive it like you stole it"
WOT/redline types, or if you're running lower than recommended octane (combustion cooling) or maybe you're running slightly higher than stock compression ratio or added a header and maybe free-flow air filters, etc.

Anyhow, that's what they told me. Do I 
"know". No. My area of expertise is safe civilian airplane driving within a controlled civilian environment. 

Always willing to learn though and welcome
knowledge, remarks from others 'cause maybe I heard wrong or misunderstood.

Cap'n. Bob      '60 :{)

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