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    Set up Instructions for Blow Through Mechanical Systems TECH

    With a K Valve –  

    The main jet- (pill) is located in the brass plug with 9/16” head.  The pill controls the flow of fuel back to the tank at all times – Larger pill = leaner mixture / Smaller pill =  richer mixture.

    The Idle adjustment is accomplished by what is known as leakdown%. You will need a leak-down tester for fuel injections  to accomplish this, or you can simply attempt to adjust the hex rod that connects the K Valve to the Butterflies-

    The Butterflies are pre set to approx.. 005”  to .010” – do NOT adjust them to achieve an idle – only adjust the rod to richen or lean the mixture at idle. This adjustment has no influence on power, all idle only.

    As the barrel valve is forced to move in the normal direction of travel it gets richer – Move it backwards to lean the idle. Expect a 1500-1600 rpm Idle NO less. These systems do NOT idle down low. They like 1800 rpm.

    Information for a Square Barrel Valve is the same except the By pass pill will be located in an external pill holder connected to the  fuel inlet fitting. Otherwise all information is the same.

    Boost referenced Fuel Flow Control Valve:

    This is the heart and soul of a boosted mechanical system.

    This valve begins  at wide open and is controlled by  a 3lb pressure valve coming from the barrel valve –  The 3 lb keeps it from flowing fuel while the fuel pump is trying to initially get fuel to the nozzles.  After it idles, the pump makes  around 5 lbs, so it opens that valve and fuel rushes to the tank. Since boost is non existent yet, there is no need for much fuel flow. This fuel valve  is controlled by boost, so more boost causes it to close, less boost keeps it open longer. When boost climbs, it  will close at a pace that keeps up with fueling needs. The ratio of operation of this valve  is controlled by a Jet or pill holder which you put inline from your boost source and send it to the -6 fitting on the Flow valve.

    The LARGER the pill – the more boost it will apply thus closing the valve sooner.

    The SMALLER the pill, the longer the valve will allow fuel to go to the tank causing leaner conditions which work with less boost. So Big pill for Big boost, small pill for smaller boost.

    Now you see that you have three major adjustments:

    Main jet – pill

    Boost Flow valve – pill

    Barrel valve – Leakdown idle adjustment


    We have installed a pressure valve  between the barrel valve and the POWER nozzles to stop them from  opening until boost is sufficient to handle the fuel from the POWER nozzles – You will HAVE to tinker with the pressure settings of this valve to achieve the power nozzles opening at the correct time. More shims in it result in making it open at a higher pressure which keeps the power nozzles closed longer – Less shims = less pressure which will open them sooner –  So now you have the 4th adjustment. This is the most difficult adjustment to make, since you have to do some guessing about where your boost is coming in to allow the use of more fuel to the power nozzles sooner or later.

    IDLE NOZZLES – The Idle nozzles are always flowing, the engine runs comfortably on idle nozzles with low to no boost, and of course, eventually the system will cause the power nozzles to join them as boost comes up. Your job is to figure out when and how much.

    Shut off valve:

    All mechanical systems have shut off valves so you can stop the flow of fuel to the engine in an emergency, or when you want to drain the system or put it up after racing. You can also pull the shut off valve back some to lean the system out during warm up at idle to cause it to get hot quicker, the hotter the better up to around 1100  degrees. You can expect approx. 500 degrees on the headers at a 1500 rpm idle and overall 1050-1150 peak EGT on methanol at Wide open  peak. Over 1200 is too hot, so use a smaller pill in the main or a smaller pill in the boost referenced valve, or larger power nozzles part # 7007.

    Alkydigger also sells a primer kit which will let you  push a switch and make the system flood itself to get it started, since you cannot squirt a Blow Through setup easily. You can install a device in the HAT to let fuel drizzle onto the butterflies which will cause it to start, then close off whatever opening you used to let fuel in. Our setup uses a pressure nozzle to flood the distribution block. We install the primer valve in the distribution block, but we do not furnish the rest of the primer kit with it.

    Sizing the Nozzles and main jet pill :

    This is part of the initial design –  Based on Engine size, turbo or Pro-Charger size – static compression – fuel type etc. we size match the fuel pump, idle nozzles, power nozzles, power nozzle check valve pressure for an initial setup –  We CANNOT tune these systems, only you can. They cost 20% of an expensive EFI system, and offer  plenty of power and tons of adjustment, but you don’t have the computer doing the tuning like you do on the $12,000 setups.  

    So in summary

    You can now see how you have 7 different adjustments:  

    Main jet, pill in the flow valve, pressure to the power nozzles, Barrel valve leakdown for idle, and the size of the idle and power nozzles.

    Our leakdown tester is:   part # LeakdownAD   

    Idle nozzles are part # 7007-E

    Power Nozzles # 7007  

    Main jet pills # 7009