What are valves?

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Old 08-21-02, 12:46 PM
0-60in5
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What are valves?

What are valves and how do they apply to an engine in terms of how good or fast it is?

Thanks.
 
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Old 08-21-02, 05:31 PM
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valves on a 4 cycle engine is what allows fuel air mixture into cylinder and exhaust out of the cylinder as far as performance there is two aspects to consider on alot of late model stock vehicles they use 4 valves per cylinder which allows more even distribution of the fuel air mixture into the cylinder and better exhausting capability of the cylinder the result is a little better performance and lower emissions, but the same princable on a more radical racing engine is done for just more horsepower, and often uses a different combustion chamber design than what a stock vehicle would use.
on a small block chevy engine for example alot of people try to run the larger intake and exhaust valves due to their larger size the valve will flow more and increase power the engine creates due to it getting a larger amount of fuel air mixture into the cylinder and exhausting the cylinder more effectively, but if all you did to a small block chevy was change the heads to a larger valve sized heads you would likely see no benefit at all, it takes a port matched intake good flowing exhaust and porting and polishing of the cylinder head along with the right camshaft for the application it will be used for, to really increase the amount of horsepower the engine creates, and relativly large gains can be made with the right head, intake, and exhaust combination.
 
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Old 08-22-02, 08:24 AM
josh1
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typically valve speak is done in MM size of what you are running. Valve seats can be cut at different angles 3 degrees etc for better performance. Stainless valves with stellite facing are used for "no lead" conversions of older cars. some cars use 4 valves per cyl some 2 some use 5. some use 1! i prefer 1 for simplictiy but they cant all be A series. Big valve heads flow more air. More air= more fuel/air in the cylinder. Engines are not 100% VE. The cylinder is typically only 80% filled so much can be done to improve engine performance. ( not forced induction thats a horse of a dif color) If you increase valve size on a FI car youd probably need to adjust the stock sensors to handle the increase airflow. However if its a good old carb ( insert WEBER here ) then you can get it to a rolling road and adjust the mixture.

Hope this helps-josh
 
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