[darbikrash]

Originally Posted by RocktimusPryme

That is awesome. I have been halfway considering a centrifugal unit on my firebird. This would for sure be an option as well. Im just concerned that if I added 150 HP I would be past the limits of the stock 400 block.

Centrifugals are a good option as well. They do have very different boost characteristics as compared to twin screw blowers. Typically, centrifugals make their boost at a much higher RPM, with little boost down low where most street driving is done.

For a pure drag car, I think a centrifugal would be a better choice.

My goal with this project was to get a package that could be used on the street, fit under the hood, and make decent power even for a guy with unported cast iron smog heads and low compression. With this example, if you keep a sensible redline of 5500 RPM (or lower) you make all the power with cylinder pressure-not by revving it.

This is a lot easier on a stock block, and you can get respectable HP numbers and still get by with less than a full aftermarket block.

Not trying to say a forged bottom end and an aftermarket block aren’t an advantage- of course they are, but with modest boost, a sensible redline and the tight engine management that comes with sequential EFI, you can do a lot.

Here is a graph from Richard Holdner who probably dyno tests more blower motors than almost anybody, comparing boost curves from a twin screw (in this case a Kenne Bell) with a Vortec centrifugal.

Notice how flat the twin screw boost curve is across the range, and how little boost the centrifugal is making under 4000 RPM.