Many people have the impression that a supercharger is an exotic performance part found on wild street machines or race cars. There is also the impression a supercharged vehicle is difficult to drive on an everyday basis. Nothing could be further from the truth on both counts. 

First, a supercharger is nothing more than a large air pump that can provide greater than atmospheric pressure (Boost) to an engine. When was the last time you thought of an air pump as exotic? 

Second, when building an engine for supercharging (other than a racing application), it is generally built for low to mid-range torque and power just as a stock engine would be. Because an engine may be left stock when utilizing a supercharger, your vehicle or boat would be no more difficult to operate or maintain than prior to being supercharged. As you can see, a supercharger is really not exotic. It is really quite practical.

The guidelines below have been established to assist in building a supercharged engine. They are applicable to the Pro-Street and 671 thru 1471 superchargers. The specifications are for a basic street supercharged engine.

Engine durability and dependability are two factors given strong consideration in these guidelines as WEIAND's current supercharger kits were developed for everyday use. WEIAND superchargers are; however, quite capable of being used reliably in competition. The information given has been developed from over 30 years in the supercharger business. 
 
 

The extent of the engine preparation will depend entirely on how the engine is to be used. A supercharger can even be installed on a stock engine with cast pistons and a cast crank as long as moderate boost (below 5 pounds) is maintained and any detonation is strictly controlled. 

Engine speed should also be limited to 5000 rpm. Detonation on cast pistons can easily break ring lands. Too much boost and/or detonation on a stock or worn engine can cause piston damage or burned valves.

Most late model "smog" engines work well with a supercharger due to their lower compression ratios and smaller cam profiles. 
 
 

1) 7.0:1 to 9.0:1 COMPRESSION RATIO: With the standard blower drive ratios supplied in WEIAND's supercharger kits, the optimum compression ratio is 8.0:1.

2) 4-7 psi BOOST LEVEL: The drive ratio provided in WEIAND's supercharger kits will net this boost level on the average engine. This range of boost has proven to be the best compromise for power and reliability.

3) ENGINE RPM: When using stock cast pistons, the engine should be limited to a maximum of 4500-5000 rpm. Exceeding this limit may over stress the cast pistons causing failure. Blueprinting an engine using the proper components will allow higher rpm reliability and fuller realization of a supercharged engine's potential. 

4) DETONATION (Pinging): Detonation is the single most destructive force in a supercharged engine and steps must be taken to eliminate it. This may include lowering boost level, retarding timing, increasing fuel flow to prevent leanout or using a fuel additive to raise octane level. The cooling system also needs to be in good condition to prevent overheating, which may lead to detonation.

If an engine is to be driven hard or under load, as in a boat or towing, a thorough blueprinting should be considered. Forged pistons, with their inherent strength and ability to withstand higher temperatures, are recommended. Follow the piston manufacturer's recommendations for piston-to-cylinder clearances. 

A compression ratio exceeding 8.0:1 is not recommended, nor is it necessary for brisk performance from a supercharged engine. If raised to this level, fuel, ignition timing and total boost become critical factors. Detonation may occur and steps will need to be taken to control it (ref. note #4). 

Next consideration would be the piston rings. They should always be the best quality available because the piston rings take as much abuse as any other component in an engine. "Moly" or "Double Moly" piston rings (iron piston rings coated with Molybdenum Disulfide) are an excellent choice for supercharged street engines. They seat quickly and wear well. For hot street or competition, where higher boost rpm will be used, chrome or stainless steel piston rings should be considered. 

Consideration should be given to using heavy-duty fasteners especially on the connecting rods and main caps for added durability and strength. Unless the engine will be run with a high boost level (12 psi or more), it is not necessary to O-ring the block. Fel-Pro's high-performance head gasket with built in stainless steel O-ring is recommended because it can withstand the higher combustion pressure and temperatures encountered in a supercharged engine. 
 
 

Weak valve springs or burned valves can lead to backfires. When an engine has more than 50,000 miles on it inspect the entire valve train. If the valve springs require replacement, factory heavy-duty springs should be used. With the use of an aftermarket camshaft, follow the camshaft manufacturer's recommendations for valve springs. 

For proper cooling of the valves, use a three-angle, "street-type" valve grind. With the additional combustion temperatures normally generated in a supercharged engine, the wider valve seats will provide better cooling of the valves, and the three angle valve grind will provide better sealing of the valves. When any port work is being done, most of the effort should be directed to the exhaust ports. The supercharger will overcome most minor restrictions on the intake side of the cylinder head.

Camshaft Selection: A supercharger can overcome inadequacies in a stock cam up to about 4500Ð5000 rpm. You will typically find that performance with a blower will not be significantly enhanced below these speeds with a cam change. However for optimum performance at higher rpm's a more aggressive cam will provide substantial power increases.

For best performance with a blower you should look for a cam that has higher lift and longer duration on the exhaust side. Street performance with a blown engine is usually best with a cam that is ground on 112 to 114° lobe centers. Blower cams can be typically run "straight up". Note that a blower has tendency to lessen the rough idle of radical cams. 
 
 

Air Cleaners: Good quality air cleaners should always be used on a street supercharger. Allowing dirt or debris to go through the supercharger may score or gouge the rotors or case.

Exhaust System: The less restriction the better. Use large tube headers with low restriction type mufflers. Low speed torque will not suffer by using larger primary tube headers as is typical on unblown engines.

Carburetion: At full throttle a blown engine can require 50% more air than an unblown engine and as a result needs a larger carburetor(s) in order to produce full power. If your blown engine is primarily driven on the street at moderate engine speeds (under 4000 rpm) you won't need a larger carburetor(s). However, to make maximum power and boost you will usually need a larger carburetor(s). 

Typically the carburetors(s) will need to be enriched by 5 to 10% on the primaries and 10 to 20% on the secondaries. The idle mixture screws may need to be enriched by one or two turns. In either case, the carburetors need to be jetted properly to prevent a lean condition. A lean condition can lead to overheating and detonation. 

For initial start-up, it is better to have a slightly rich condition to help prevent the engine from overheating. After initial start-up, check the spark plugs for proper reading (color) and adjust the carburetor(s) accordingly. You want to see a medium to dark tan color. 

Pro-Street 142-177: In some cases on an unmodified stock engine, the original 4V carburetor may be utilized. If a replacement carburetor is to be used, a unit in the 600 to 800 cfm for small block and 750 to 850 cfm range for big block is recommended. Vacuum secondary carburetors work well, with a double pumper being the choice for highly modified engines.

Pro-Street 256, 671 thru 1471: Experience has shown that a pair of 600 cfm carburetors work well on most small block applications. We do not recommend single carburetors on these applications. Big block engines equipped with 671 thru 1071 blowers typically would use two 750s or for heavily modified engines two 850s. Double pumper carburetors are the best choice. The 1271 and 1471 application require 1000+ cfm dominator carburetors.

Fuel System: An inadequate supply of fuel may cause a lean condition which could lead to detonation and overheating. An excessive supply of fuel may cause puddling of fuel in the manifold, which could lead to backfiring.

Pro-Street 142-177: The stock fuel system will be adequate for some applications. If the engine will be run hard on occasion, upgrading the fuel system should be considered. To upgrade, a high volume, mechanical or electric pump mounted near the fuel tank, used in conjunction with the fuel pressure regulator, is recommended. Fuel pressure should be adjusted to the carburetor manufacturer's specifications. A good quality fuel filter should also be incorporated into the system.

Pro-Street 256, 671 thru 1471: A good quality high volume electric pump should be used to ensure an adequate supply of fuel. Mount the pump next to the fuel tank and use a minimum 3/8" ID fuel line to the carburetors. For big cubic inch engines with larger carburetors 1/2" ID fuel line should be used. Use a regulator to maintain fuel pressure at the carburetor using the carburetor manufacturer's specifications. A high quality fuel filter should also be used.

Ignition System: Set the initial timing at 6 to 10° BTDC. The distributor advance curve should be calibrated to give a total advance of 28 to 34° in by 2500 rpm. Most late model OE electronic ignition systems have the capability of working well with a supercharger. Some distributors with computer controlled advance curve and timing, may not be compatible with a supercharger because of the preset timing and sensors they require. Any of the aftermarket, high performance standard or electronic distributors should function well when properly calibrated. A good quality, electronic unit would be the preferred choice for best all around performance and reliability. If detonation is encountered a boost/retard system that works with manifold vacuum and pressure is recommended (not recommended for marine). 
 
 

Pro-Street Supercharger: Because of their smaller size the Pro-Street 142 - 177 (small block) and Pro-Street 177 (big block) are operated at higher drive ratios than the larger 671 thru 1471 or 256 blowers. These faster blower speeds are more efficient at lower engine speeds and less at higher engine speeds than the larger blowers. As an example, the standard 142 Pro-Street Supercharger for the small block is supplied with a ration of 1.95:1 ratio. This ratio is optimized for a 350 cid engine and will typically provide 5 to 7 pounds of boost on this size of engine. 

The reason we cannot provide an exact boost figure is that camshaft profiles, cylinder head configuration, and carburetor size can all have effect on the amount of boost that will be shown on the boost gauge. To illustrate, if you have a small port heads and a stock cam, at higher engine rpms the blower will be unable to overcome these restrictions and boost will build up in the manifold producing an artificially high boost reading. Conversely, changing the cam and heads will make the boost reading go down but the power will increase at higher engine speeds.

If you are running an engine larger than 350 you will get less boost than you will get on a 350 and if you have a smaller engine you will get more boost. Boost is a direct result of three factors: engine size, blower size and the speed the blower is driven in relationship to the engine speed. Bigger blowers driven at the same speed as a smaller blower will produce more boost. Weiand offers a full range of pulley sizes that allows you to optimize your boost for your specific engine combination.

Our small block Pro-Street 177 supercharger is also optimized for a 350 engine and will provide approximately 5 to 7 pounds of boost with a 1.71:1 drive ratio. The big block 177 is optimized for a 454 engine and uses a 1.95:1 drive ratio.

The Pro-Street 256 for the big block is driven at slower speeds than the 177 since it is almost 50% larger in size. This blower uses a wider 16 rid Poly-V drive belt because it can produce substantially more boost than the smaller blowers requiring more horsepower to drive the blower which calls for a bigger drive belt. This blower is supplied with an upper pulley that is optimized for a 454 engine and will provide approximately 5 to 7 pounds of boost with a 1.40:1 drive ratio. Optional pulleys for more or less boost are available.

Street 671 thru 1471: These bigger blowers can be driven at substantially slower speeds than the smaller Pro-Street units and still provide optimum boost levels. All 671 thru 1471 Weiand Supercharger Kits are underdriven. Each drive ratio was selected to provide an optimum boost level in the 5 to 8 pound range. This level of boost will allow the blower to be run on engines with compression ratios in the 8.0 to 8.5:1 range. 

If you desire a substantial change of boost you can just interchange the top pulley for the lower pulley and change the blower from underdrive to overdrive. However, swapping pulleys will approximately double the amount of boost you will get. Normally decreasing the upper pulley by one tooth or increasing the bottom pulley by one tooth will raise the boost one or two pounds. Conversely increasing the tooth count on the upper pulley or decreasing the teeth on the lower pulley by one tooth will lower the boost by one or two pounds.

Weiand offers a wide range of both 1/2" and 8mm pitch drive pulleys that will allow you to tailor your boost level to a particular engine for optimum power. 
 
 

Weiand 671 thru 1471 and Pro-Street blowers require little in the way of maintenance. Because they are machined and setup to operate with tight clearances, there is no rotor-to-case contact and no Teflon "wear strips" to replace. In addition to making sure the rotors turn freely (check immediately if engine backfires!), monitoring lubricant levels is important. A non-pressurized reservoir of gear oil (80W-90) is maintained in the front cover (and rear cover of Pro-Street blowers). 

We recommend changing oil every 6000 miles when operated daily. 671 thru 1471 blowers have sealed rear bearings that may require changing after 50,000 miles. If boost pressure drops dramatically the unit should be overhauled. Call Holley technical service for details regarding superchargers.