The advantage of the Kinsler adjustable high-speed valve (part #3904HR) over the “jet can” that was most commonly used in the past is that it has less internal friction on the moving parts inside and it has a much larger area for the pressure to act on for regulation, resulting in a valve that opens closer to the same RPM every time.
It is easily adjustable by using a blade screwdriver and a 7/16ths-inch wrench, which eliminates dropping and losing parts or dealing with leaking fuel when changing settings.
Like the quick-disconnect, changing pressures on a red is made easier.
Lastly, the Cadillac of high-speeds – the Kinsler K-140 – has the highest flow capacity with the lowest pressure rise of any valve on the market. For most applications, the rise is under one psi, since the total bypass flow for most systems is 600 lbs/hr or less.
With extremely smooth operation, the closing flow curve is within .3 (3/10) psi at any flow point on the opening curve. This is achieved by hard coating, then microlapping, all of the moving parts. This means the pressure in the fuel system will stay close to the set point on both rising and falling engine RPM.
Many valves experience a “buzz” (hydraulic vibration); this valve is more stable as it is the only valve on the market with a unique spring arrangement designed to control the hydraulic vibration.
The K-140 has a swiveling live center pintle that closes down on the seat for a smooth operation. Both the pintle and seat are lapped for a ‘bubble” tight close-off. With the hard anodized finish, this valve is compatible with gasoline and methanol.
Different spring combinations allow for an adjustable range of 17-230psi.
TUNING TIPS AND BASIC ADJUSTMENTS
Turning the screw in on a diaphragm-type high-speed, or putting a heavier spring and/or adding more shims in a jet can-type high-speed, will raise the pressure at which the valve opens, making the system richer on the top end.
The high-speed is usually adjusted to start opening at about 500-1000 rpm above peak torque. If a high-speed is installed on a fuel system when it is calibrated by your engine builder (usually done when your engine is dyno‘d), the main jet and high-speed bypass settings should be very close for optimum power.
Due to varying weather conditions across the country throughout the racing season, if the fuel system doesn‘t seem to have the ideal set up as when it left your engine builders dyno:
1) If the fuel curve seems too rich throughout the rpm range, go to a leaner main jet.
2) If only the top end seems rich, go lower on the high-speed pressure setting until the high rpm mixture is correct.
A) If the system has a restrictor jet, try going .004”-.010” larger per run.
B) If the system still seems rich after step ‘A,‘ lower the opening pressure of the high-speed by approximately three psi. Note: It is recommended that you reinstall the original restrictor jet before lowering the pressure setting.
C) If the engine still seems rich with the lower pressure setting, repeat step ‘A.‘ While this method may require several runs of the engine, it has to be found to be a safe way to tune the system while avoiding engine damage from going too lean!
3) If the system is adjusted to give a proper fuel curve but the overall curve needs to be richened or leaned due to changes in the engine displacement, air density, weather, altitude, etc., adjust the high-speed pressure for each main jet step you adjust.
4) Tune the engine for best performance, not just what appears to be good plug readings!
**Important Note: When properly adjusted, a high-speed bypass engagement should not be felt by the driver. If the driver feels the high-speed bypass engage, because the engines power increases dramatically, then either the main jet is adjusted too rich or the high-speed is opening at too high of an RPM.
Either condition will cause the engines output to be lower than optimum. There should be no sudden burst of power, only a steady strong pull.
RESTRICTOR JETS
The pressure setting of the high-speed is used to control the RPM at which the valve opens, while the restrictor jet is used to limit the flow after it opens.
The smaller the jet, the less fuel that can flow through the high-speed and back to the tank, thus richening the system at higher RPM levels.
In some oval track applications, the use of a restrictor jet assures that the high-speed does not dump off too much fuel at high rpm part throttle (i.e. coming down a straightaway and quickly closing the throttles causing a pressure spike).
The high-speed will open and start returning fuel; the restrictor jet will then restrict the amount of fuel bypassed during this overrun condition.
If you own a high-speed bypass valve that doesn‘t have a provision for a restrictor jet, simply use a jet can after the valve by removing the poppet and stretching the spring out to hold the jet in place.
Make sure the jet can has a jet sealing O-ring.
The fuel system is the most critical part of an engine and how it performs on race day.
Be sure to listen to your engine builder and what he has to say when giving you instructions on fueling your engine, and be sure to keep an eye on the weather throughout the night as the changing conditions will affect the performance of your engine.
Unless you have an Outlaws style budget and carry six or more engines with you at all times, you cannot afford to “burn” one down!
In addition to the engine builders, all of your fuel system specialists (such as Waterman, Hilborn, DSR, Enderle, etc.) will also be able to lend a helping hand.
I want to personally thank Greg Murchison at Kinsler for his help and information for this article.