Alright guys as you know I am building a 400 sbc. I am wanting to go full tilt with this thing but still keep it with its creature comforts. Is it worth it to put aluminum under drive pulleys on the engine. Will it help performance any noticeable amount or is it just a big waste of cash?
It will not noticably affect your performance, but it will keep the alternator from charging properly putting more of a load on the diodes in it, and cause unintented cooling issues as well.
I use aluminum pullies to convert away from V-belts (which are becoming harder to find) over to serpentine belts which can not be thrown, or rolled at high engine RPM. (if you are buying new pulleys anyway it makes sense to upgrade to a better system I use two seperate belts so that I keep my normal rotation on my Stewart phase II high volume aluminum water pump needed to cool a higher than stock horsepower engine).
Nope Alan (BA) offers expert advise all the time, as well as Big Gear Head occasionally. You can look at the number of posts these people have offered and raise their reputation by clicking on the scale icon in the top bar of the post. Don't know if it will do anything for them but it is a little way of showing your appreciation that doesn't cost anything.
Underdrive pulleys and street use don't go together for all the reasons Dave mentioned. If you're looking for a little extra HP at the track they might help but those situations call for quick chargers on a strong battery and cool downs between runs.
If you're still running the older alternator mount way off the valve cover it's a good idea to run a deep groove alternator pulley for V belts, especially if you have a high RPM small block. That long belt can fly off or roll over and shred.
If you plan on using the car on the street (in traffic) you would be much better off to overdrive the W/P pulley (water pump pulley smaller diameter than the crank pulley) and use a high flow water pump & thermostat. For track use the opposite would tend to free up some horsepower.
I prefer a Stewart water pump that has a CNC machined closed impeller designed to work in a precision machined housing with double row of ball bearings instead of bushings and a cast iron open paddle wheel like the stock water pump does. That way I don't have to over drive or under drive anything. It moves twice the volume of water with one third less horse power drain because all work goes into pumping the water not heating it by a loose paddle wheel allowing water to recirculate with the pump cavity due a poor fit. Stewart pumps are used on all NASCAR class cars that are Chevy powered (sorry they don't make a water pump for a Jap car when last i looked). Very few people have ever even heard of the company as they are a little secret that allows me to keep another seven horsepower I would otherwise loose.