What was the cubic feet per minute rating for the 1964 Pontiac GTO tri power carburetor
Executive summary
The 1964 Pontiac GTO "Tri-Power" setup—three Rochester 2G two‑barrel carburetors—does not have a single universally accepted factory CFM number in the sources provided; enthusiasts and specialists report total flow estimates that cluster between roughly 700 and 950 CFM depending on how the smaller two‑barrel ratings are converted to a four‑barrel standard and which year/part variant is referenced [1] [2] [3].
1. The heart of the dispute: no factory CFM label found in the cited materials
No source in the provided reporting gives an unequivocal factory-published total-CFM figure for the 1964 Tri‑Power; Wikipedia documents the Tri‑Power as an optional three‑two‑barrel Rochester 2G arrangement and the Tri‑Power’s horsepower figure but does not list a carburetor CFM value [1], while parts lists from The Parts Place supply casting and part numbers for the 1964 Tri‑Power center/front/rear carbs without a flow rating [4].
2. How enthusiasts convert two‑barrel ratings to a comparable 4‑barrel number
A major reason for the wide variation in reported totals is that original Rochester two‑barrel CFM ratings were often measured at a 3.0" Hg pressure drop, whereas standard four‑barrel ratings use 1.5" Hg; community practice is to convert 2‑barrel ratings to a 4‑barrel equivalent by multiplying by about 0.7071 (or dividing total 2‑barrel flow by √2), an approach explicitly described in forum analysis and used to produce “total” Tri‑Power numbers [3] [5] [6].
3. Common numerical estimates from the hobby press and forums
Using the conversion logic above, one piece of forum math calculates the center carb as ~269 CFM and each outboard carb ~326 CFM for a summed total of about 921 CFM (after conversion) and notes a community consensus in the 900–950 CFM neighborhood [3]; other forum threads and the Pontiac Tripower FAQ/analysis cite lower totals—typically in the 700–800 CFM range—either because they start from different two‑barrel castings or use alternate conversion approaches [2] [5] [7].
4. Independent comparisons and contextual references
The Pontiac Tripower website and related articles emphasize that measured CFM figures for 1964–66 Tripower units are inconsistent and that practical dyno/track comparisons sometimes show the Tri‑Power feeling like a significant power gain over single four‑barrel setups, but the site also notes sightings of Tripower estimates in the 700–800 CFM range and references magazine tests rather than a factory spec [2] [8]; a Muscle‑car piece and parts/specialist pages compare Tripower results to Holley or Carter single four‑barrel baselines without asserting a single canonical Tri‑Power CFM [9] [10].
5. What a straight answer looks like, given these sources
Given the absence of a factory CFM stamp in the available documentation and the multiple community conversion methods, the best supported conclusion from the supplied reporting is that the 1964 Tri‑Power total flow is estimated by experts and enthusiasts at roughly 700–950 CFM depending on how the two‑barrel numbers are normalized to a four‑barrel standard—commonly cited specific tallies include ~750–780 CFM (after one conversion) and ~920–950 CFM (after another), both of which appear repeatedly in the provided forum and specialist material [2] [5] [3].
6. Caveats, alternative viewpoints, and where to go next
This synthesis reflects the numbers and conversion methods found in Pontiac‑specialist sites, enthusiast forums, and parts catalogs in the reporting; it does not claim a single factory-printed CFM because none appears in the supplied excerpts [4] [1] [11], and specialist restorers warn that venturi casting differences, jetting, and testing conditions materially change measured flow—so those seeking a precise dyno‑verified CFM for a specific carb casting should consult original Rochester spec sheets or perform flow bench testing on the exact carb castings and jetting in question.