How to Build a Supercharger Engine

Few cars on the street command as much attention as a car with a 6-71 supercharger sticking up through the hood. From the mind-boggling power and response to the awesome looks and sounds, it's worth every cent. Not only does it look good, but it increases gas mileage, as long as you are driving like a normal human being (as opposed to a speed demon). It is shocking to see 18 miles per gallon on a 350 cubic inch supercharged engine.

Things You'll Need

• 4-bolt main Chevy block
• Clevite bearings
• Steel crank
• Fluidamper harmonic balancer
• Short snout water pump
• ARP bolts
• X rods or pink rods
• Childs and Albert total seal piston rings (top ring)
• Forged aluminum pistons (floating pin type)
• Speedpro piston rings (second and bottom ring)
• High flow heads
• Blower camshaft
• Felpro headgaskets
• Copper headgaskets (optional)
• 6-71 Blower (Weiand is a good brand)
• 2 450cfm Holley carburetors
• 2 850cfm Holley carburetors (optional)
• Low profile distributor
• MSD-BTM
• Exhaust evacuation system

Instructions

1. Follow all of the steps for building a supercharged engine, and it will last as long as a normal engine. Everything imaginable breaks on supercharged engines, so learn and know what it takes to keep it together -- learn from someone with 40 years of drag racing experience and learning the hard way.

2. Purchase all the parts. Send the block to the machine shop--in addition to the normal work done on a standard block, you will need to have the block magnafluxed and checked for line bore. The machine shop will also put the rods on the pistons and size the rods to the crank for you. Have the machine shop insert a double keyway in the steel crank and the harmonic balancer.

3. Put the engine together. When you get to the bearings, make sure there is no more than .003 clearance on the main bearings. Use the Childs and Albert piston rings for the top ring, and the Speedpro rings for the other two.

4. Check the total compression of the engine combination you chose. It should not be more than 8.5:1 total compression on a blower motor. Once under load, the compression will increase dramatically with the blower.

5. Make sure the camshaft is cut for a blower, as it works more on the exhaust side. This is very important, as it will need to match with the rest of the block and the heads. The lift of the camshaft will also figure in the overall power of the engine.

6. Put the high flow heads on the block. If you plan on racing this engine, you should use the copper headgaskets. If you are simply going to be fooling around on the street, the Felpro gaskets are fine. Be sure to use the ARP bolts when putting the heads on. The high flow heads should have larger exhaust valves, strong springs, stainless valves and bronze seats. Again, this is important--what goes in must come out.

7. Add the short snout water pump and the fluidamper harmonic balancer. The typical long snout Chevy water pump will hit the blower belt, so this must be changed out. The fluidamper harmonic balancer needs to be a one-piece harmonic balancer. The typical rubber harmonic balancers will disintegrate.

8. Finish off the engine up to the intake manifold. Add the blower. Use the 6-71, as the 8-71 is for fuel injection (which is very expensive and generally only used in racing applications). Do not tighten the supercharger bolts more than 12 to 14 foot pounds, as they are aluminum, and designed to break away.

9. Top the blower with two 450cfm carburetors (or two 850s if you are going to be racing). You will need to have a high volume fuel pump and a fuel pressure regulator. You do not need additional pressure to have enough fuel for the blower -- just volume.

10. Use a low-profile distributor (nothing else will fit). A trick is to use a points distributor with an MSD-BTM box. The distributor points only act as a switch for the MSD and do not burn out.

11. Install the exhaust evacuation system with one-way valves on the headers so they can rid the crankcase of blowby; this helps power and economy while protecting the engine. They should not be angled more than 15 degrees, or else you will have too much vacuum, and that will suck the oil out of the valve cover.

Tips & Warnings

• When tightening the blower belt, leave it very loose to start. Once everything gets going--usually after a minute or two--the belt tightens up on its own. Run the engine a bit on the rich side (this helps to keep the cylinders cool), and use no more than 32 degrees of advance. Set the MSD-BTM adjustable advance to retard the spark to about 28 degrees under full throttle. The header temperature at the cylinder should be no more than approximately 470 degrees F at an idle. Follow these tips when building a supercharged engine, and avoid the mistakes of many motor-heads who had to learn first hand. There have been a lot of blown blown motors, but the supercharged engine will last a long time with very little maintenance if you follow these tips.

• When installing the blower, be sure the small pulley is on the crankshaft and the large pulley is on the blower. This will produce about eight pounds of boost. If you reverse the pulleys, the pressure increases to close to 22 pounds of boost, and this will make parts disappear really fast. Turbo chargers run high boost pressures, but roots-type superchargers like the 6-71 put out tons of volume with lower pressure.