Chevrolet's Gen I small-block Chevy engines have a great track record over the last 50-plus years-powerful, simple to build, and tough as nails. When the Rochester mechanical fuel injection was introduced, we never dreamed that 1hp per cubic inch was even possible. Today 500 hp or more is easily obtainable and streetable. What an engine!
Many years ago, there was a '62 Corvette making the rounds around south Florida propelled by a 301 small-block that ran a Duntov 30-30 solid lifter camshaft that shattered the hopes of many would-be contenders on Saturday nights. That's just one of the many reasons the small-block became one of my all-time favorite engines many years ago.
We sent the new GM block to...
We sent the new GM block to Gerald and Charlie's Machine shop to have it bored 0.030 over by Daniel for the previously purchased Wiseco pistons. As you can see, no torque plate was used during the boring process. We are using a (green) new block that will change as it ages, and we don't feel the torque plate will make a substantial difference in this street/strip application.
For those of you not familiar with the 301 engine, it was an early 283ci cylinder block bored to 4 inches. Those early blocks had extra-thick cylinder walls that allowed opening up the cylinders. The 301 was as bad as they came until the 327 was introduced in 1962. Aftermarket small-block parts are all over the place now, from discount auto parts retailers to mega-performance suppliers. We also have many giants in the automotive industry that have taken on the small-block and built these engines to astounding horsepower-per-cubic-inch numbers.
All of this helps those of us who love the small-block and want all we can get from these lightweight engine blocks. Along with the Internet, you can find the info and parts to build any cubic-inch small-block at any horsepower level depending on your budget. The toughest parts of any small-block build are what parts to choose, and deciding whether to build it yourself or buy a complete crate engine. It's hard to beat a crate engine nowadays because, in most cases, the cost will be less for the same components. Crate engines require large production facilities and use parts in larger quantities to allow the more competitive pricing.
Our situation was somewhat different. The owner's original intent was to build the numbers-matching engine in his '85 Corvette, but the first engine build went sour and damaged the original '85's engine block. The situation then dictated using the previously purchased pieces, if possible, to recoup at least a portion of the original build costs. The original plan was to stroke the '85's engine to 383 inches to allow for a longer duration camshaft and high horsepower without sacrificing low-rpm grunt.
Daniel goes to work honing...
Daniel goes to work honing the block, while careful to keep the correct crosshatch pattern by carefully timing the up-and-down motion of the hone and not exceed the 0.004 piston-to-cylinder clearance we decided on. There's a fine line that needs adhered to when fitting pistons. Too loose and piston slap occurs; too tight and cylinder walls are scored from the tight fit. The crosshatch pattern helps retain oil in the cylinder during the break-in period.
Our task in this 383 build is to make 450-500 hp using the parts at hand from the previous builder's pieces and follow the original concept as close as we can. Before we get too involved with the horsepower and torque numbers, rotating mass friction should be considered. The norm was to keep the crankshaft bearing clearances loose and run 20W50 oil along with STP to add more viscosity. Friction created by the high-viscosity oil costs power and fuel mileage from drag at the crankshaft main and connecting rod bearings. The added load on the oil pump also requires additional horsepower that will eventually instigate more wear on the distributor driven gear and cam gear.
When bearing clearances are kept between 0.0015 and 0.002, 10W30 oil can be used successfully even in high-rpm engines. So our first order of business is to keep the clearances tight and use Royal Purple synthetic 10W30 oil to fight heat degradation.
The rotating assembly from the first build consisted of an Eagle 3.750 stroke crankshaft and Eagle 6.0-inch connecting rods. Wiseco flat-top pistons would provide a 10.41 squeeze ratio with the Edelbrock Performer 64cc combustion chamber aluminum cylinder heads. We decided a new GM four-bolt main cylinder block was in order, but we would need a one-piece to two-piece rear main seal adapter to allow us the use the Eagle crankshaft, connecting rods, and Wiseco pistons that were previously purchased.
As we mentioned, we're locked into the short-block build of the engine due to our previously purchased parts, but we can make some changes in cam timing and ancillary pieces to boost horsepower.
We used Virtual Engine Dyno software to build our engine virtually and configure our optimum torque and horsepower numbers. Our first virtual dyno configuration horsepower numbers were 458 hp at 5,750 rpm, and our peak torque was at 4,500 rpm with 394 lb-ft of torque at 2,750 rpm. This dyno software is really cool as you can download the individual parts to make a virtual dyno run and then change them to see if the change was beneficial. Once we have the install finished, we'll see just how accurate the virtual software is.
|Difficulty Index - 5 Wrenches|
|Anyone's Project: no tools required||1 Wrench|
|Beginner: basic tools||2 Wrenches|
|Experienced: special tools||3 Wrenches|
|Accomplished: special tools and outside help||4 Wrenches|
|Professionals Only: send this work out||5 Wrenches|