Big valve conversions

Car tuning tips:Intake Valve tips"

Intake Valve tips Guide

The job of the intake valves is to control the flow of air and fuel into the engine, and then released exhaust gases after combustion.  The intake valves have quite a hard life due to the rapid opening and closing, and have a big impact on the performance of the engine. 

The intake valve is shaped much like a trumpet and is pulled shut when its job is finished. If it does not close fully you will lose power from your engine, and risk damaging the intake side of your engine as the flame front seeps through the gap.

Larger valves allow you to have a larger intake aperture and will allow more air fuel into the engine, and more effectively expel the exhaust gases.  As an alternative to larger valves, manufacturers have opted for a greater number of valves.  There is no reason why you cannot have larger valves on the a 16 valve engine where there is sufficient clearance space within the cylinder.

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We initially had eight valve engines, where each cylinder had two valves an intake and then exhaust valve.  The next innovation was increasingly is to 16 valves which doubled the number of valves to each cylinder.  We now have Audi engines with four cylinders and 20 valves of varying sizes.

In some engines the valves are selected according to engine speed, and innovations such as the Honda VTEC mechanism effectively allows two cam profiles to control the rate of opening and closing of valves for any given engine speed. While you have the head off the engine you may as well get it fully ported and gas flowed.

 Although engines will benefit from having the valves re-seated especially if a compression test reveals a loss of compression on one or more of the cylinders.   A problem with the valves could be due to a worn lifter or cam.

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One Response to “Intake Valve tips”

  1. Damic says:

    You guys forgot the 12v’s, yeah a 12 valves 4 cilinder engines, this engine has a higher torque curve (I know I had 1)