We love naturally aspirated engines, but there's no arguing that when it comes to adding serious power, nothing beats a little—or a lot—of boost. Single turbos, twin turbos, and centrifugal superchargers have become more prevalent on the street, but root-style blowers are still a great way to shove buckets of atmosphere into an engine.
We had a cost-effective 383 small-block lying around just dying to make more power. It was built at a lower compression, partly so it could run cheaper, low-octane gas, but also because we wanted to try out some forced induction. Given the lower cost of our engine, we wanted the supercharger to make sense, so we settled on a Weiand 144 roots-style blower. The 144 is about as small a blower you can put on a small-block and, with the right hood, have it fit inside an early Camaro without any of the parts poking out.
01 The starting point for this project was the Speedway Motors 383 small-block we built at Evod Garage in the last issue. It penciled in at a wallet-friendly $4,000 in parts and made 437 horsepower and 453 lb-ft of torque. For durability, it was filled with a COMP hydraulic roller valvetrain, and to keep costs down, we used Speedway's cast rotating kit. It was built at a boost-friendly 9.0:1 compression, and since we knew some sort of forced induction was in our future, we splurged on ARP head bolts.
02 After removing the dual-plane Weiand intake and Holley 750 carburetor, we installed the intake manifold from the Weiand 144 supercharger kit (PN 7740-1 $2,300). We like that they now include the water neck since it can be challenging to track one down that fits under the blower snout.
03 Here's a helpful hint. The intake has a shelf overhang that covers the area above the oil pressure port on the back of the block. So, before installing the intake, we made sure to install a 90-degree fitting first.
04 The key player in this kit is the Weiand 144 roots-style supercharger. It's advertised to give a 25-40 percent boost in power. The reason for the large range of performance gain is that it's very dependent on what engine it's bolted to. A stock 350 would see a bigger percentage gain, using the included pulleys, than say a built 383 stroker like we're using. The blower is made with all-new parts and will work with V-belt pulley systems.
05 The blower was bolted to the Weiand intake using the four bolts included in the kit. Do not over-tighten the bolts as they only require 10 ft-lb. Any tighter and you run the risk of distorting the blower case and doing damage to the rotors. The small port just below the carb flange is perfect for reading intake vacuum. If you want to reference boost, that would have to be taken from below the supercharger.
06 The unit shipped with a 3.05-inch upper pulley and a 6-inch lower pulley. It also included a 10-rib belt to better resist slippage under boost.
07 If you're buying a carb for a supercharger, then buy the right one. In this case, we went with a 750-cfm Holley (PN 0-80573S, $560) specifically designed to work in supercharger applications. This has the capability to allow the power valve to operate as it should: off intake manifold vacuum. It also provides further enrichment to the main metering system under load (low vacuum) conditions. Without this, the power valve would read the supercharger vacuum, which has zero to do with engine load. This is the route we would go if building a supercharged engine. If converting, we would retrofit our existing 750 Holley to match these specifications.
08 With everything installed, we sent the engine back to Westech Performance's Superflow 902 dyno. For this run, we filled the dyno's tank with 91-octane Rocket pump gas.
09 After warming everything up and setting the timing to 32 degrees, we got a best pull of 502 hp and 501 lb-ft of torque. At 3,000 rpm we had a 70 lb-ft increase in torque over the NA setup, which is something you would really feel on the street. Still, not a huge boost in power for the money spent. After looking at the data we found the blower was only making max boost of 3.2 psi, which isn't much. This goes back to what we said about the kit, as packaged, working best on a stock to mild small-block. Given this, we only had one option: more boost!
10 Weiand offers a 7-inch crank pulley (PN 6813WIN, $279), but we didn't have one handy at the shop. After a little digging around, we eventually found a 10-rib, 8-inch pulley bolted to an LS engine and decided to see what this little blower was capable of. We needed a new, longer belt and found a 48-inch one at the local parts store. The Weiand pulley in the box was a two piece with a spacer and a flat pulley. This made finding a different size that would fit pretty easy.
11 We did the math on this and found we would be spinning the blower at just over 14,000 rpm. Given that its redline is 16,000 rpm, we were still in the safe zone, and there would be a nice bump in boost. We played it safe and dumped some 110-octane Rocket race gas in the dyno's fuel tank this time. The new, larger pulley really woke up the small-block and power leapt to 563 horsepower and 581 lb-ft. of torque. In this graph you can see the pull made with the 8-inch pulley overlaid on the 6-inch pulley pull. Max boost is now just over 9 psi. Also, 550 lb-ft at 3,000 rpm is just a good time waiting to happen.
12 And here's the 8-inch pulley pull compared to the best naturally aspirated dyno pull. The Weiand supercharger gave us a gain of almost 150 lb-ft of torque down at 3,000 rpm. The peak numbers shot up 128 lb-ft for torque and 126 for horsepower. When pushed, the little Weiand 144 blower really came through, and our budget-minded small-block shined as well. Money spent on the right parts really made a difference, even when trying to keep the overall cost of the project in line with reality. This combo is even sweeter since the smaller pulley could be run on the street, and then we could swap to the bigger one, dump in some higher octane, and hit the track. Another good option would be running the 7-inch pulley mentioned earlier. It falls right between the other two and should be good for right around 6 psi of boost, with power numbers in the neighborhood of 530 horsepower and 540 lb-ft. It's nice to have options, and that's one area where forced induction has naturally aspirated beat hands down.