Holley is misrepresenting their HP carb flows, a HP 950 is really a
830, a HP1000 is about a 870 if measured the same vac as a 47-- series. The industry standard for cfm ratings was 1.5"Hg vac for a 4 barrel. holley decided to follow the deciptive lead of it's competitors and use 28"wc which is 2.06" hg. Holly has all their carbs listed with flow spects. They make no distinction between a HP type and a older 4781 type. Unless you actually flow a carb, with holley's listings, you can't tell what flow it may be since the listed flows of the 4 barrels are not made with the same test standard. Their all listed together by flow ratings. I'm just for the truth in advertising, if holley actually told the test vac for carbs it would be better, Esp if they use different test spects for different 4 brl carbs. It looks like Holley uses a 1.5"HG vacuum standard for the 47_ _ series carbs and for the HP series they use 2.06"hg vacuum test standard. The result is a false comparison between the two carbs. I got tricked and many others will be also. Spread the word about this .The HP950 has a 1 3/4 base plate and a 1 3/8 venturi. A older 850 has a 1 3/4 base with a 1 9/16 venturi A HP830 has a 1 11/16 base and a 1 9/16 venturi