{"id":21675,"date":"2015-11-24T08:32:01","date_gmt":"2015-11-24T16:32:01","guid":{"rendered":"http:\/\/www.racingjunk.com\/news\/?p=21675"},"modified":"2016-11-30T13:56:40","modified_gmt":"2016-11-30T21:56:40","slug":"holley-tri-power-series-part-2","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/holley-tri-power-series-part-2\/","title":{"rendered":"Holley Tri Power Series Part 2"},"content":{"rendered":"

\"carburetor\"<\/a><\/p>\n

Check Out – Part 1<\/a> –\u00a0Part \u00a03<\/a> – Part 4<\/a><\/p>\n

Last issue<\/a>, we previewed the intake portion of Holley’s brand new three-deuce setup for the small block Chevy. \u00a0If you recall, the intake is a 180-degree dual plane Weiand that is setup for street use. \u00a0It accepts conventional cathedral bowl Holley two barrel carburetors with a maximum throttle bore size of 1.50-inches. \u00a0Those Holley carbs are the focus in this issue of “The Burnout”.<\/p>\n

The manifold is engineered to accept a 325 CFM Holley carb in the middle, accompanied by a pair of 350 CFM carburetors. \u00a0That’s a lot of CFM – 1,025 in total, and certainly too big for a street-driven small block. \u00a0But there’s a catch here (and one that a big print competitor of ours failed to notice in their review of the system): Two-barrel carburetors have their CFM ratings performed at a different pressure drop than similar four-barrel carburetors. \u00a0Here’s how it works:<\/p>\n

A two-barrel carb is tested (for flow) at 3″ Hg depression. \u00a0On the other hand, four-barrel carburetors are flow rated at 1.5″ Hg depression. \u00a0These are the industry standards for carburetor airflow testing.<\/p>\n

As you can see, the two-barrel test depression is double the four-barrel test depression, however flow varies with the square of depression. \u00a0That means that it’s easy to convert from one test depression to the other. \u00a0Here’s the formula:<\/p>\n

Divide the cfm by the square root of the pressure it was flowed at, and multiply that by the square root of the pressure you want to calculate for.<\/p>\n

500cfm \/ (sqrt of 3) = 288.675134595<\/p>\n

288.675134595 x (sqrt of 1.5) = 353.55339059<\/p>\n

That\u2019s the hard part. There\u2019s a simpler way (but perhaps not quite as accurate) to accomplish the conversion:<\/p>\n