Quote:
Originally Posted by Tom Vaught
All 950 HP carbs and 1000 HP carbs were rated (for advertising purposes to compete against Barry Grant's claimed air flow numbers.
If you test a 950 HP carb at the same 20.4" water test pressure as the 780 vacuum carb and the 750 DP carb, the cfm will be with-in a few cfm of the old 750/780 carb airflow numbers.
Same deal with the older 4781 850 cfm double pumper carbs and the rare Corvette Vacuum Secondary cards. 20.4" of water you will get 850 870 cfm not 1000 cfm.
20.4 was used forever before the Barry Grant days and he changed the carb flow test pressure to the higher 28" of water test pressure for marketing purposed because Smokey said the HP was closer on his dyno using the 28" test pressure vs dyno testing.. Again an advertising game. And again people like to brag about "leroy" being bigger in their pants/ carb.
Tom V.
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Good info Tom. I'm more curious if the OP is using the original 3310 with down leg boosters. A bit surprised a 3310 with straight leg boosters would out run a 850 vacuum secondary on his combination, but the choke housing and air cleaner choice may have contributed to the performance difference.