Editing Choosing a carburetor

{{newarticle}} ==Selecting carburetor size== The higher the engine can rev, the greater the required CFM. However, bottom end response worsens with increased CFM. ===Based on displacement and use=== For a street engine, a general rule is 1.5 to 1.7 times the displacement equals the necessary carburetor CFM. For a competition engine, it can be up to 2.0 or 2.5 times the displacement. ===Based on RPM and volumetric efficiency=== Another way to figure carburetor size is with this formula: RPM x CID/3456 x VE. (VE = volumetric efficiency). A basic, run-of-the-mill engine might have 85% volumetric efficiency. A well planned-out motor can achieve 100% volumetric efficiency, and finely-tuned racing motors can reach up to 120% volumetric efficiency. ==Selecting carburetor type== ''this section needs additional opinions and confirmation'' Opinions vary on the choice between vacuum secondaries and mechanical ("double pumpers"). However, generally speaking: *Gas mileage is better with vacuum secondaries. *Mechanical secondaries are generally best suited to light, manual transmission vehicles. *Mechanical secondaries are preferred for racing applications. *Mechanical secondaries are more difficult to tune. ==Selecting carburetor brand== Most carburetors, no matter the brand, with effectively do the same function (push the gas, pull the linkage, and open the venturi's; works like that on 1, 2 and 4 BBL's). However, the quality is higher in some brands over other brands; example being Edelbrock > Rochester. *** Edit: If you'e saying Edlebrock is a better quality carb than Rochester, that's a subjective statement, kind of like saying Coke is better than Pepsi. Edelbrock makes aftermarket, universal carbs that must be tailored to a specific engine, whereas Rochester carbs where made for specific vehicle/engine/transmission combinations. == Holley == Holley carburetors have been around for a long time, and their quality is fairly good. They manufactured carburetors for GM in the 60's, and have been a favorite among hot rodders through the years. Holley has several different models for different applications. ***Edit --- Ford used Holleys in the 1950s, maybe even earlier. GM began using in mid 60s when Holley released the 585 CFM 4 bbl, which replaced smaller Rochester 4 bbls used in 2x4 setups, as well as 3x2bbls on high performance engines. Here are just a few: -Holley 4412S -- a 2 barrel, 500 CFM carburetor that is ideal for a good ratio between CFM and economy. For a 2 barrel, its pretty large. Works well on a stock 2 BBL manifold for engines such as a 327 SBC -Holley 80457S - Decent 4 BBL carburetor that produces 600 CFM's. It uses mechanical secondaires, so economy takes more of a "backseat" on this one. Would probably be ideal for your daily driver/mild build. This is about the average 4 BBL sized carburetor ***Edit --- The 0-80457 is actually a vacuum secondary carb, not mechanical, with electric choke, and is in the 4160 family. All 4160 carbs are vacuum secondary. I would use the 0-1850 as an example a basic 600 CFM carb, and the 0-3310 as a 750 CFM example. And I'd start by describing the various carb families, like 4150, 4160, 4175, etc. Newer and more popular carbs are Street Avenger series of 4150 carbs. By the way, the S or C after the carb list number designates the finish. S = shiny, C = zinc chromate. I can do a complete write-up here, or you can simply go to Holley's website for the facts. -Holley 80531 - This carburetor is for the Big blocks only, with a spankin 850 CFM. There is little to no economy with this bad boy; this is for the cars that do wheelies off the line. For use of 502 CI or bigger engines. Features vacuum secondaries, and a dual fuel inlet. This is for your race type motor ''' == Edelbrock == ''' Edelbrock is another top name in carburetor. They make carburetors for all types of applications From Street applications to racing to marine, Edelbrock has been another top favorite among hot rodders. They manufacture top quality carburetors, and like Holley, have different models for different applications. Edelbrock Performer Series Carburetors (500, 600, 750, & 800 CFM) - These 4 BBL carburetors offer a range of versitality for all engines. The smaller 500 and 600 CFM models would be good on engines such as a 305, 327 or 350. Like the Holley's, they are good for mild builds/daily driver. Unlike the Holleys, they have vacuum secondaries, so theres a mid-way between performance and economy. (*** Edit: most Holleys, in fact, have vacuum secondaries.) Models vary with CFM output Edelbrock Thunder Series (500, 650 and 800 CFM) - Similiar to the Performer series, but with a few variations. The 500 CFM model is designed for dual-carb setups, and cannot be used as a single. Good for medium build small blocks and some big blocks, such as the 396. *** Edit: there are, in fact, 500 CFM Thunder Series carbs for dual quad and single quad applications. Edelbrock also makes the only carburetor that is designed for Lowriders; designed for extreme angles such as the popular "3 Wheel motion", it keeps the fuel in the float bowl there constantly so you dont have "pedal lag" when driving on these angles. See Edelbrock.com for more information ==References== *http://www.hotrodders.com/forum/carburetor-size-162801.html *http://www.hotrodders.com/forum/vacuum-vs-mechanical-secondaries-131129.html ==See also== *http://www.ford-trucks.com/article/idx/18/140/article/How_to_Choose_your_next_Carburator.html *http://www.thirdgen.org/pickacarb *http://www.classictrucks.com/tech/cl_0312_choosing_carburetor/index.html ==Books== *How To Build Horsepower, Volume 2: Carburetors & Intake Manifolds, by David Vizard. ISBN 1884089143 [[Category:Engine]]

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