Project Chevelle 383 Engine Tech Article
This is the moment we've all been waiting for. The little 307 that has been quietly puttering our '72 Chevelle around for 46 years is finally getting a well-deserved retirement. Rest well, little buddy.
We're pretty excited about the bullet that we've selected to take its place. BluePrint Engines is a couple hours up the road from us, and they keep our shelves stocked with everything from mild short blocks to crazy, big power monsters. We shot for something in between, and came up with a 383 that promised a perfect compromise between polite street manners and brutal horsepower. BluePrint claims 420 horsepower (more on that later) and 450ft./lbs. Should be just about right.
This engine starts with a 4-bolt block and uses a steel crank and hypereutectic pistons to squeeze 10:1 compression. The BluePrint aluminum heads help keep that number pump gas friendly and breathe through 195cc runners and 2.02"/1.60" valves. The cam is a hydraulic flat tappet that measures 229/230 at .050" with a 110 LSA and .488/.486 lift. Nothing wild or exotic here, just tried and true street hardware.
Not only does our new engine need to make power, it also needs to look like it belongs under the hood of our 70's street machine. To that end, the perfectly adequate but slightly ugly HEI distributor that came with the engine got the boot in favor of an MSD Digital E-Curve distributor. If you squint, it looks a bit like an old points distributor, but comes filled with modern electronic wizardry. The traditional mechanical and vacuum advance contraptions have been replaced by a circuit board and some knobs. With these, you can dial in an advance curve that's perfect for your engine without fooling around with tiny springs and weights.
We also chose a Holley 770cfm Street Avenger carburetor. We have used these in the past and really love them on street engines. Vacuum secondaries, electric choke, and traditional Holley tuneability make them particularly well-suited for street-driven hot rods.
Once the carb and distributor were in place, we hauled the new crate across the street to Speedway Racing Engines. They spend most of their time building race-winning sprint car engines, and they have a couple dyno cells for proving the power of their engine packages. They let us sneak in every once in a while to do a little testing, and were kind enough to bolt the 383 to one of their dynos and make a pull or two.
So how did it come out? How about 431 horsepower at 5300 rpm? That's over three times (!) the power of the 307. Not only that, but the torque curve was super flat, with 452 ft./lbs. coming in around 4000. That's one of the advantages of a 383; the added stroke helps that torque number. A combination like this is particularly well suited to a heavy car like our Chevelle.
Once we had the new engine back in our shop, the period-correct detailing continued. The whole works was painted Chevy orange, including the aluminum heads. You'll hear people say that this can't be done, but a good cleaning and scuff followed by some parts-store engine enamel will hold up pretty well and hide the modern cylinder heads in a vintage engine compartment. We also pulled a set of our Holley Muscle Series valve covers that are identical twins to those used on the early 70's LT-1 engines. Add the white headers and a reproduction dual-snorkel air cleaner and the new engine looks like a refugee of the 70's horsepower wars. Perfect.
We have a few other surprises to throw at the old Chevelle before we can drive it around with the new engine, so stay tuned for the installation and a driving report. Until then, let that beautiful 430 horsepower music play in your dreams and imagine rowing through the gears in a hot rod Chevelle. That's what we're doing and it's keeping us going through the rest of the work that needs to be done.
Stay tuned, this is just starting to get good.