Hotrods, muscle cars and all go-fast junkies normally end up on the road for more and more speed. To get this monstrous speed and make it down the quarter faster, most gravitate towards a few things the layperson knows little about. Injection and blowers (known as superchargers by some) are at the top of the list for this niche to boost up power and speed. These can be combined with different gas alternatives to make a motor either blow up or go really fast. I’m just as interested as the next guy in going fast, and blowers look the coolest in my opinion, along with making great performance when you dial them in correctly. I knew about as little as the next guy in this matter, so I headed over to Walden’s Speed Shop in Pomona, CA to get a handle on blower basics. Walden’s Speed Shop are pros at putting power and cool-as-hell looks together. I knew Bobby Walden had a few tricks up his sleeve, as he’s an amazing hotrod builder with an addiction to blowers. He says, “Everyone needs a vice, mine is blowers.” With a vast knowledge of blowers, he knows how to make them work, and work well. Let’s start off with the basics – blowers can be found in three different styles: roots, screw (or Whipple), and centrifugal (or Paxton). Roots superchargers are the most common type you’ll see out there and are Bobby’s favorite to use. The modern roots style blower has evolved from use on GM diesel and is where the identifying call numbers come from. 4-71, 6-71, and 8-71 are identifications you’ll quickly see if you start searching Jegs or Speedway for a supercharger – and they tell you everything. The first number denotes how many cylinders the diesel had and 71 is the size of the combustion chamber. So that being said, multiply the first number by the second one and, Bob’s your uncle, you’ve got the cubic inches of the motor the supercharger originally came off of – getting you in the ballpark on selecting the one you should use for your own application. Before we get too far into beginning blowers basics, it should be mentioned that Bobby’s first piece of advice to the enthusiast going down the supercharged path is be realistic about what you’ll be using your engine for. Unless you just have tons of money to blow and want something novel, average hobbyists often overestimate how much horses they need for their Sunday driver and end up throwing down a ton of money on parts that aren’t necessary for their application. Back to the numbers… Bobby explained to me that a 4-71 works awesome on a small block style V-8 and a 6-71 should be used for a big block V-8 (or a higher rpm small block.) There are people that run the larger 6-71 on small blocks, but Bobby explains that when the air starts coming from the blower, pressurizing the block, air cavities in the manifold warm up and get hot. This extra heat will work its way up to the carb and make the fuel hot, which isn’t good. A 4-71 on the other hand pushes just enough air to force the air fuel mix into the combustion chamber and keep the motor cool, always pulling cold air in. Good for power! If you’re starting down this road for yourself, begin with an engine you know has good compression and very little leak down. Don’t necessarily go out and buy an all-in-one street build up kit, those often have lots of parts that are a waste of money. However, do look for blower parts that go together – it’s not just a supercharger you’re buying, you also need a manifold, pulleys, tensioner, and brackets. If you’re building nostalgic, some of these parts are super rare. Even though it’s becoming common to find remade parts, they might add up to costing more than the blower itself. Internal components can all be replaced, so if you’re shopping for something vintage there’s no need to worry about whether the bearings are good. Bobby’s engine of choice is a stock 383 small block Chevy. Easy to get, affordable, and they are a great crate motor. Then it’s all bolt on with your 4-71 blower components. Does the cam need to be changed to take on a blower for this type of setup? Bobby said not at all, these two are a match made in heaven. If you’re considering doing a more unique vintage engine, Bobby highly suggests talking to your engine builder first and getting the best machine shop possible to do the machining work, this an area where paying for the best will make a difference! Bobby’s addiction has continued to shape Walden Speed Shop, so much so that he now CNCs his own covers, plates, and pulleys with a growing line of blower parts available. He’s a good person to talk to if you’re considering a vintage-style blower powerplant for your next ride – there are so many variations out there you can do, so get creative and start looking for parts! Walden Speed Shop | www.waldenspeedshop.com
