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Dark Knight · 08-12-2001, 10:01 AM

found this... http://www.ondoperformance.com/tech.html

kinda interesting... ;-)
United States, most carburetors are rated in flow capacity at a test pressure of 20.4" of water, (1.5" of mercury, 51.8 cm of water). An 850 cfm (4001/s) carburetor is one
that passes 850 cfm of air at 8 test pressure of 20.4" (51.8 cm) of water. However, if you observe a manifold vacuum gauge on a racing engine at full throttle, you will see
that it only reads about 0.5" of mercury (6.8" of or 17 cm water). At a test pressure of 6.8" of water, the same carburetor would only pass 490 cfm (2301/s) of air. This is
why carburetor ratings appear to be all out of proportion to engine requirements.

------------------
84 convt,'95 302,AFR's, performer
3.55's, underdrives BBK shorties
stock cam, 1.7's
13.85@102.5
and a '68 stang that WAS nasty ;-)

08-12-2001, 10:01 AM	#29
Dark Knight Registered Member Join Date: Oct 1998 Location: Az Posts: 854	found this... http://www.ondoperformance.com/tech.html kinda interesting... ;-) United States, most carburetors are rated in flow capacity at a test pressure of 20.4" of water, (1.5" of mercury, 51.8 cm of water). An 850 cfm (4001/s) carburetor is one that passes 850 cfm of air at 8 test pressure of 20.4" (51.8 cm) of water. However, if you observe a manifold vacuum gauge on a racing engine at full throttle, you will see that it only reads about 0.5" of mercury (6.8" of or 17 cm water). At a test pressure of 6.8" of water, the same carburetor would only pass 490 cfm (2301/s) of air. This is why carburetor ratings appear to be all out of proportion to engine requirements. ------------------ 84 convt,'95 302,AFR's, performer 3.55's, underdrives BBK shorties stock cam, 1.7's 13.85@102.5 and a '68 stang that WAS nasty ;-)