Choosing a carburetor
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[edit] Selecting carburetor size
The higher the engine can rev, the greater the required CFM. However, bottom end response worsens with increased CFM.
[edit] 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.
[edit] 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.
[edit] 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.
[edit] Selecting carburetor brand
basic explanation of the various brands goes here. should include: parts availability, quality, difficulty in tuning, price, etc.
[edit] References
- http://www.hotrodders.com/forum/carburetor-size-162801.html
- http://www.hotrodders.com/forum/vacuum-vs-mechanical-secondaries-131129.html
[edit] 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
[edit] Books
- How To Build Horsepower, Volume 2: Carburetors & Intake Manifolds, by David Vizard. ISBN 1884089143
