High horsepower has always been the hallmark of a hot rod. The horsepower wars are alive and well at the factory level and increasingly the OEMs are using superchargers to get the numbers. Forced induction has been a standby for hot rodders for over half a century. Traditionally you will see a huge blower protruding out of an equally huge hole cut from the hood and topped with towering carburetors. The factory keeps their installations lower key. Most of them fit under the hood or at least under a scoop of some sort. In our case we wanted to add some more power, but also drivability and have it all fit under the stock hood of our ’75 Chevelle station wagon. While hacking a hole in the hood or bolting on a cowl induction hood has its place, it would certainly take away some of the sleeper-factor. So we came up with an ultra-low profile combination of parts for a killer induction system.
Our starting point is a standard 350 small-block Chevy with a bottom-end torque cam, Brodix IK180 aluminum cylinder heads, Hooker headers, an Edlebrock Performer intake, Q-jet carb and HEI. Compression was about 9 to 1 so; overall, it seemed like a pretty good package but in a relatively heavy car. To be honest it was not performing to our expectations, thus the search for some additional power. It was also giving us tuning fits. The Q-jet was recently rebuilt but would not respond to tuning attempts, and had a bad fuel pump as well. So with our plan for new parts and more horsepower we tore into it and didn’t look back. We knew straight away that we needed the lowest huffer we could find, and because this was for a 350 Chevy, we could use a Weiand 144. The 144 installs .75” lower than the 142 due to a different intake manifold; therefore, it was our ticket to success. For our setup there just wasn’t any room to add another accessory to the front of the engine.
The Weiand roots type blowers have been around for decades and are proven technology. You haven’t heard much about them in the last 10 years or so because of the popularity of centrifugal designs but each has their place for solving different packaging limitations. Not only is the technology proven on this blower but the installation package has had all the bugs worked out years ago so the installation is very straight forward. Just about everything bolts to the top of the engine. It is about as simple as a manifold swap but definitely cooler looking.
The fuel mixer was our next challenge and we were rapidly running out of height for this combination. A typical Holley or Q-jet carb was going to be too tall if we expected to run an air cleaner. So we selected the Holley Avenger EFI system because the throttle body had the lowest overall height and the computer could handle boost when tuning the engine. We wound up with a combination that was just 1” taller than the Q-jet/performer manifold currently on the engine. Because we were running a 4” tall air filter we could step down to a 3” for the time being until we could add the cowl induction hood at a later date.
The blower coupled with the EFI will give us the power boost we want as well as the drivability we are seeking. Today, it is expected that a street machine be as well mannered, or at least not as temperamental, as it is fast. The days of boost referenced carburetors or finding the guru that knows all the tweaks have passed. You can now buy your own guru and it comes in a little black box. Technology is a great thing and it has done wonders for performance cars. This project combines older technology (roots blower, small block Chevy) and newer technology (EFI) to achieve something that is drivable on a daily basis.