We get many phone calls and emails from people wanting to fit a supercharger to there engine, not all want huge power increases but want that cool blown look. Yes you can super charge a standard engine. To many customers the who do i listen to, where do i start and how do i sort out what are facts and what is crap. This is just a few things that might help you when it comes to making the decision to go blown. To give a real incite we could write chapters and chapters on every thing in detail but the whole point of this is entry level information.
We have been involved with hundreds of customers from all over the world with there supercharged engine projects. Rover V8 engines in the United Kingdom, early Holdens all over Australia, Chevy 6s in Norway, Canada and the United States plus a few Chevy Big and Small Blocks, Slant 6 Chryslers and a fair few V8s.
So the first fact from bull shit is forged pistons are a must. If you are building a performance engine and going for high horse power going through the engine and doing a bunch of machine work yes i personally would consider a forged piston. The main failure we have seen in blown engines is caused by detonation. Detonation is normally the limiting factor in any forced induction engine. Trying to explain to someone that the difference in run time when an engine is detonating with either cast or forged pistons is about 3 seconds. A common area that a piston will fail is above the top ring and the crown of the piston.
Engine venting is another area that is often over looked and apart from making a mess on your garage floor and all over your engine bay if you have a bit of engine blow by / piston rings are sealing as well as they could, the oiling system can be pressurised and if that pressure cant get out of the engine there is a good chance seals and gaskets can leak. Rocker cover venting is the best place to start and big breathers are a good place to start as well as vented catch cans, evacuation system through the exhaust and oil return feeds.
Valve springs are something that needs to be addressed in a supercharged engine, when you fit a supercharger the blower spins and forces additional air into the engine and when this happens it puts extra force on the back of the intake valve. We have seen engines on the dyno hit around 5000 rpm and see boost pressure in the manifold rise, the horse powered doesnt continue to rise and the engine will not continue with its nice flat torque curve. Not always but it can be caused by the intake valve not completely sealing and not getting full on valve bounce but a bit of what we call valve flutter.
Exhaust systems headers/extractors on any blown engine should be upgraded. When you have more air being forced in you need more fuel to burn that air and as the efficiency of the engine is improved you need to get rid of that burnt charge. So increasing header/ extractors exhaust system size on a blown engine is something we consider important.
Ignition systems are another area that should be addressed. More fuel, more air a better spark is really going to help burn it. If you are buying a complete new ignition system look at some of the systems that are available with boost retard. As the engine starts to make boost the ignition system will retard the timing by a certain amount of pre set degrees for every pound of boost the engine makes.
Cylinder head seal is also something that should be addressed if you are doing a rebuild or removing your cylinder head or heads. Yes head stud kits are a great idea but if the head and block are not flat to begin with it doesnt matter how much you spend on a head gasket you are going to have problems.
Harmonic balancer is really where the supercharger starts at when it comes to the drive system. check the outer rubber and the key in the crank. We have seen on many manual engines that the balancer key can wear out the key way groove in the balancer hub so correct fitting and alignment and a centre retaining bolt is a good idea. Also as hard as it is not them clutch dropping take off and flat changes between gears can take there toll on that little woodroof key so keep an eye on that.
Compression ratios is something else that we could bang on about for ever. In short the more static compression you start with will limit the amount of boost the engine can take before detonation occurs. A faster spinning blower will generate more charge heat and things like special oxygenated race fuels, water methanol injection, E85 will all help in raising the death rattle that can be associated with a blown engine.
So my suggestion is if you want to go to a supercharged engine and you have an engine that is complete and running and have time to play and see the improvements that can be made along the way start with a stocky or with what you have. Get your blower kit, talk to a cylinder head shop near by and there are tools available for changing valve springs without removing the cylinder head. If you put in to much timing, not enough fuel, to much boost its better to learn from your mistakes on a second hand junkyard engine than a big dollar purpose built engine first time round. Your big dollar engine with its high quality parts will go bang just as quick if you get things wrong.