Blower Drive Services      



All BDS Blowers are assembled by hand with heavy duty competition components. The same parts used to assemble our Top Fuel blowers are the same parts used in all of our blowers. Heavy duty bearings and special double lipped Teflon seals are used to ensure long life. The heavy duty bearing plates and cases are machined to precise specifications that produce the most efficient blower possible. All BDS blowers are fully show polished as a standard feature. Unpolished blowers are special order.

Blower Efficiency and Specific Blower Applications

In order for a supercharger to perform up to its maximum potential, it must be assembled, clearanced, and setup specifically for the application for which it will be used. BDS categorizes these differences by "Stages". Specify which Stage suits your requirements when you place your order or let the experts at BDS determine the correct Stage for you. CAUTION: failure to follow the guidelines outlined below could result in blower failure. BDS is not responsible for failures due to the improper use of blowers. The different Stages and their intended uses are as follows:

Stage 1
Used in almost all street applications using "pump gas". Capable of producing a maximum of 12-15 lbs. Of boost in most systems, not exceeding engine speeds in excess of 7000 RPM.

Stage 2
Used in high performance street systems, bracket racing, marine and/or dirty racing environments using high octane gas. The interior of the blower is hard anodized for added strength and efficiency. Capable of producing 15 lbs. Of boost and more on engines turning in excess of 7500 RPM.

Stage 3
Used for high performance racing applications on gas. Hard anodized and Teflon stripped on the lips of the rotors. This blower is capable of very high boost levels and high engine RPM. Designed for street, strip and off shore systems.

Stage 3.5
Same as stage 3 but utilizes billet rotors for a higher efficiency and a longer life between restripping.

Stage 4
Used for high performance racing applications using alcohol and/or nitro-methane for fuel. Hard anodized and stripped with both Nylatron and Teflon, this blower is capable of extremely high boost levels and engine RPM's. Intended for competition use only.

Stage 4.5
Same as stage 4 but utilizes bilet rotors for a higher efficiency and a longer life between restripping. This blower is front discharged for maximum performance.


BDS Polished Drive Kits are manufactured from aircraft aluminum and steel alloys to ensure maximum performance and durability. A number of options are available to customize your Drive Kit for your specific requirements (see the Blower Kits and Drive Kits Options section in this catalog).

Accessory vee grooves can be provided to drive the water pump, alternator, power steering, and air conditioning accessories. All Drive Kits utilize a steel crank hub with two key ways (stock and 1/4") to replace the stock factory harmonic balancer. For more information on harmonic balancers and crank hubs, please refer to the Blower Crank Hub section in this catalog.

These drive kits are easily adaptable to steel balancers as a custom drive kit.

The complete BDS Drive Kit comes polished and includes:

  • Blower Gear Coupler
  • Drive Snout
  • ½ pitch Upper Blower Pulley
  • Idler Pulley
  • Idler Mounting Assembly
  • ½ pitch Blower Belt
  • Steel Crank Hub
  • Accessory Vee Groove (s)
  • ½ pitch Lower Blower Pulley
  • Bolts
  • Spacers
  • Gaskets
  • Instructions
  • Complete Blower Kits:

    Small Block Chevy 671 Kit $2550
    Big Block Chevy 871 Kit $2800

    Final Compression Ratio Chart

    This chart shows the final compression ratio combining the static compression ratio of an engine and the maximum blower boost from the blower system. It is to be used as a guideline in determining the proper maximum boost level for a specific application. Final compression ratios in excess of 12.4:1 are not recommended for use with "pump gas." The higher the final compression ratio, the higher the octane rating of the fuel must be in order to help prevent detonation and serious engine damage.

    Corrected Compression Ratio = FCR - [ (altitude÷1000) x 0.2 ]


    COMP RATIO 2 4 6 8 10 12 14 16 18 20 22 24
    6.5 7.4 8.3 9.2 10 10.9 11.8 12.7 13.6 14.5 15.3 16.2 17.0
    7 8 8.9 9.9 10.8 11.8 12.7 13.6 14.5 15.3 16.2 17.0 17.9
    7.5 8.5 9.5 10.6 11.6 12.6 13.6 14.6 15.7 16.7 17.8 18.6 19.5
    8 9.1 10.2 11.3 12.4 13.4 14.5 15.6 16.7 17.8 18.9 19.8 20.9
    8.5 9.7 10.8 12 13.1 14.3 15.4 16.6 17.8 18.9 19.8 20.9 21.9
    9 10.2 11.4 12.7 13.9 15.1 16.3 17.6 18.8 20.0 21.2 22.4 23.6
    9.5 10.8 12.1 13.4 14.7 16 17.3 18.5 19.8 21.1 22.4 23.6 24.8
    10 11.4 12.7 14.1 15.4 16.8 18.2 19.5 20.9 22.2 23.6 24.8 26.0
    10.5 11.9 13.4 14.8 16.2 17.6 19.1 20.5 21.9 23.4 24.8 26.2 27.6
    11 12.5 14.0 15.5 17.0 18.5 20.0 21.5 22.9 24.5 26.0 27.5 28.9



    Q: Can I use a roller cam for the street?
    A: Roller Cams will work in most applications as long as the camshaft grind is designed for blower applications.

    Q: What carbs do I need to run and why 2 of them?
    A: The size of carb(s) or CFM required for a given application can be calculated by the following formula A: {(CID x RPM) / 3456} x {Boost: 14.7) + 1} = CFM required. The amount of CFM required will determine carburetor size and quantity. If you try to use a carb with less CFM than required, performance and economy may be greatly reduced.

    Q: When do I start making boost?
    A: The amount of boost and the RPM at which boost starts is controlled by the throttle, blower size and drive ratio, engine size, camshaft profile, and exhaust system. All of these factors determine the breathing capability of the blown engine. Boost should only be measured at wide open throttle at 6,000 RPM. If there is only part throttle, the blower cannot get enough air to overcome the demands of the engine. Only when the blower can get enough air will there be boost.

    Q: Why are my exhaust pipes red-hot?
    A: Exhaust pipes get red hot for two basic reasons. Either the ignition timing is incorrect or the engine is running extremely lean. There are other cause but extremely critical. Blown motors love advance. Without enough initial timing advance, blown motors will run hot and the exhaust pipes will glow in the dark. Blown motors should run as little as 16 degrees or as much as 26 degrees initial advance with the total advance of about 32-36 degrees at 2500 RPM to 3000 RPM. Specific timing requirements depend on compression, blower drive ratio, engine load, camshaft, and fuel octane.

    Q: Why do your recommend such low compression when my buddy's system is running 9:1 and it's running good?
    A: Low compression enables two things to be accomplished. One, the lower compression lets us run higher blower boost producing more low end and midrange torque and two, when the engine runs coolly and effortlessly making the engine last a long time.

    Q: Why does my engine run hot?
    A: Over heating of a blown motor may be cause by too high compression ratio, too high blower drive ratio, improper timing, poor water flow through manifold, or an inadequate and inefficient cooling system.

    Q: How does retarded timing attribute to overheating?
    A: Ignition timing deals with the time at which ignition occurs during the compression stroke. Retarded timing ignites the air/fuel mixture closer to maximum compression than advanced timing. Higher compression at the point of ignition means hotter temperatures form the burning of the air /fuel mixture and this translates into a hotter running engine.

    Q: Which is stronger, 1/2 pitch or 8mm drives?
    A: The 8mm, round tooth profile is capable of transferring as much as 40% more power than the 1/2" pitch, square tooth profile. As a general rule 1/2" pitch is good up to 12-15% overdrive on most blower applications. Large blowers and high drive ratios should use the 8mm or 14mm, round tooth design.

    Q: How much space does a blower drive take in front of the engine?
    A: The amount of space on front of the motor for the blower drive system depends o the width of the blower pulleys and the number of accessory vee groove pulleys needed for each application. An easy rule of thumb is to add the width of the blower pulleys to the front edge of the vee pulley furthest from the engine block.

    Q: When I start my car it backfires, why?
    A: There are many reasons why an engine will backfire but the most common problem with blown motors is holding the throttle open while cranking the engine over. It is better to give the throttle a few pumps (2), and take your foot off the accelerator before turning the engine over and count slowly to ten. When the engine does fire and begin to run, quickly catch the throttle and raise the engine idle at about 2000 RPM until some heat can be built in the motor, about two minutes. Trying to engage the engine before enough heat is built usually results in an engine that spits, sputters, backfires, and/or dies.

    Q: Do I run an oil line from the blower to the engine?
    A: BDS recommends using a self-contained, 90 wt. Heavy duty gear oil lubrication system for the blowers. Contaminating the engine oil in the motor with 90 wt. Oil can cause some engine lubrication problems and increase the likelihood of detonation.

    Q: Should I use gapless rings?
    A: Testing with gapless rings in a supercharged engine shows excellent increase in performance.

    Q: Steel or aluminum rods, which are better?
    A: Both styles of rods are well suited for blown applications. Steel rods are generally used on motors that must produce a ling service life. Aluminum rods are generally used for engines seeking high horsepower output and not long service lives.

    Q: Can blower whine be eliminated or made louder?
    A: Blower whine can be increased or decreased by tightening or loosening the blower belt tension. CAUTION! Improper belt tension can cause severe belt, blower, and engine damage. It is not recommended to adjust the belt to get the sound you want. Worn pulleys and belts as well as mis-machined pulleys can contribute to blower whine.

    Q: What kind of headers should I use?
    A: Steel, or stainless steel headers may be used. Engines with 400 CID or less should have exhaust tubes at least 1 3/4 " to 1 7/8" diameter and larger engines should use 2" and bigger. Forcing more air in with the blower requires more exhaust to be passed through the exhaust system.

    Q: My engine builder is determined not to use a crank hub o my blown motor, only a harmonic balancer. What do you say?
    A: We do not recommend any type of cast iron balancer because they break easily. Any hi-quality heat-treated after market steel harmonic balancer with two key ways (one 3/16" and the second a 1/4" key way located 180 degrees apart) will perform very well. Be sure to notify BDS at the time you order your blower kit if you will be using an after market harmonic balancer. BDS will accommodate this kit change when ordered initially. On any large cubic inch high horsepower system we recommend that you use our heat-treated heavy-duty 4130 chromally steel crank hubs.

    Q: My car won't idle?
    A: Idling problems with blown motors is usually a result of a severe vacuum leak, improper ignition timing, or improperly adjusted carbs or fuel injection.

    Q: My plugs are black?
    A: Black sooty plugs is a direct result of too much fuel. The carbs or fuel injection is not properly adjusted or set up for your engine, correct your fuel delivery system.

    Q: Where should my timing be at?
    A: Blowers love ignition advance. Especially initial advanced. For most blower applications, the initial timing should be set at 16-26 degrees initial advance with a total of 32-36 degrees advance, in all by 2500-2800 RPM. More advance can be run if there is not a detonation problem. Some vacuum advance systems will have as much as 45-50 degrees total advance under part throttle, cruise conditions.


    The following information as compiled from over twenty-eight years of supercharging experience on a wide variety of engines. The suggestions and recommendations below are for gasoline engines to be used on the street unless otherwise specified. The information is broad in nature and intended to be used as guidelines only.


    BDS suggests that the engine block be in good condition and not overboard excessively. Two bolt mains are adequate for most mild applications with boost levels up to 7lbs. Four bolt mains are recommended and are considered a must for high performance systems. O ringing is recommended for engines running 12lbs. of boost or more. When rebuilding, the block should be thoroughly checked as you would in any high performance engine build up.


    Steel cranks are recommended whenever possible and are a requirement for high performance engines spinning high RPM's. cast cranks are only recommended when the boost levels are below 10 lbs. and the engine is limited to 6000 RPM. When rebuilding, cranks should not be less than a 10/10 grind and should have all the trick work as you would for any high performance engine.


    Most factory rods will work well for mild blower systems up to 8-10 lbs. of boost. Factory and after market steel rods with heavy duty rod bolts are recommended and required for high performance applications. After market steel rods with heavy-duty rod bolts are recommended and required for high performance applications. The rods should be magnafluxed for cracks, shot peened, beams polished, balanced, and bushed to size for full floating pins.


    Factory cast pistons are not recommended but may be used in very low boost (3-5 lbs.) applications. Forged, low compression pistons 7-8:1 are the best choice for performance applications. Higher compression ratios are not recommended because of overheating and excessive final compression ratios. Pistons should use full floating pins and double spiro locks or buttons for high performance applications. In cases where alcohol is used, the compression ratio of the engine should be between 10-12:1.


    Factory heads work well in most blower applications. The heads should be in good condition or have a three angle valve job. After market heads will provide increased performance. Stainless steel valves are recommended. Head modifications (porting, polishing, etc.) are not required unless high performance is the desired result. Resurfaced or shaved heads can cause problems with the blower and manifold. The secret to Horsepower is cylinder head air flow. More air flow equals more Horsepower.


    Choosing the proper camshaft would be the most important requirement for a blower motor. An improper cam will cause a variety of problems that can easily be avoided by following a few simple guidelines. Hydraulic cams are recommended if you intend to drive the vehicle frequently, require little or no maintenance, and the maximum engine RPM's are kept around 6500 or lower. Roller rocker arms are recommended. Flat tappet and roller cams are recommended for high performance applications especially where the engine will see high RPM's. Exact camshaft specifications vary depending on the performance level you wish to attain. BDS offers ten different types or Stages of cam grinds specifically made for blower motors. Refer to camshaft section for BDS camshaft specifications and their intended uses.
       If you wish to purchase your cam from one of the many fine camshaft manufacturers, we suggest using our camshaft specs as a guidline. Extremely high lift and long duration cams are recommended for high RPM, high performance racing only.
       The lobe center of the cam will plan an important role in determining the performance characteristics of an engine. Wide lobe centers (112 to 114 degrees etc.) will create higher cylinder pressure providing more horsepower with cooler burning fuel such as alcohol and methanol. We have found 110° lobe centers to produce the best overall power on gasoline.
       Whatever cam you choose, make sure that it will operate and perform properly in the RPM range required for your application.


    The overall performance of the entire engine package will be determined by the fuel induction system. Carbs work very well in most applications as long as the carbs have been calibrated or blue printed by BDS or another reputable company. Refer to the carburetor section for help in determining the correct carbs for your needs.
       Mechanical fuel injection will provide greater performance and throttle response than carbs. However, these mechanical injection systems can be quite temperamental and are recommended for the experienced racing enthusiast only.
       BDS Electronic Fuel Injection offers you the best of both worlds. Retaining all of the drive characteristics of a carburetor system with the performance and looks of mechanical fuel injection system. We deliver the 'Best of the Best', Performance-Looks-Economy with the driveability and ease of operation in a single package. For more information, please refer to the Electronic Fuel Injection catalog.


    The ignition system and advance curve are very important to a blower motors longevity and performance. The general rule for ingnition timing in a blower motor is as follows: Initial advance at idle should be set at 16-24 degrees with the total advance of approximately 32-26 degrees, all in by 2500-3000 RPM. It is very important to verify the advance curve. Locked out magnetos or distributors are recommended for racing applications only. Improper curves may cause a variety of problems including overheating. Spark plugs should be one or two heat ranges colder than the recommended stock factory plug (never use extended tip spark plugs). This is due to the higher cylinder pressure created by supercharging. Higher cylinder pressure means more heat. Ignition management systems that can vary the timing according to engine requirements are a good idea to help keep the engine from killing itself with detonation and to keep performing at its maximum.


    The cooling system for a blower motor should be in a good general operating condition. Inadequate air flow across the entire radiator at low speeds is one of the most common causes for overheating. Mechanical fans and shrouds are highly recommended. In a recent study of electric fans, especially anything from 18 to 20 amps with a 3000-4500 cfm capapbility, these fans seem to work efficiently on blower engines, but it may still require some experimenting with location to find the best operating position. A 180 degree thermostat is recommended. Water flow restrictors may also be used, however, you will have to experiment to find the size that works best with your system. Stock factory water pumps are recommended and required in most applications. After market "High Performance" water pumps work best in the mid to upper RPM ranges and therefore may not have adequate water flow at lower RPM's to keep a blower motor cool. Three core radiators or larger are recommended for most applications. Higher performance engines will require better cooling systems because of the additional heat generated by these types of engines.


    Exhaust systems are very important to the overall performance of the blower motor. The blower forces more air into the engine than it would normally take therefore the engine must be able to get rid of more air through the exhaust. Small restrictive exhausts will cause excessive back pressure, robbing the engine of power and causing additional heaing problems as well as unusually high boost readings. Large free flowing exhaust and headers are recommended choices.


    The fuel requirements for a blower motor may vary greatly depending on the application and engine/blower specifications. Unleaded fuel is okay as long as the engine is setup for unleaded fuel. The "Final Compression Ratio" of the engine/blower combination is the determining factor in fuel octane requirements. As a general rule, the maximum final compression ratio should not exceed 12.4 to 1 for 92 octane fuel. Octane boosters and higher octane racing fuel will allow you to run a higher final compression ratio. Final compression ratios should not exceed approximately 24-26:1 for racing gas.


    BDS blower kits and components are directly applicable to most marine systems. There are minor differences between the requirements for marine and non-marine applications.
       Small pleasure crafts on up to offshore racing engines will benefit from the increases in torque and horsepower supplied by a blower system.