Dart provides extra material...
Dart provides extra material on the deck of the block, allowing it to be machined to the proper height for the application. We wanted our Mahle dished pistons right at the top, which required installing the crank, rods, and pistons, then physically measuring how much material needed to be removed.
You may be asking yourself why all this machine work is necessary if we're using new parts. We'll show you. While this engine can basically be bolted together, the cylinders need to be honed to their final size based on the diameter of the piston. We'll first measure the pistons, then hone the cylinders for precise piston-to-cylinder clearance. Also, because the Dart aluminum block is customarily used with dry-sump oiling, we'll need to machine some drain holes, so the oil can find its way back to the pan. For maximum quench area in the combustion chamber, we'll mill the deck of the block so that the piston is truly at the top of the cylinder at top dead center. We'll also cut deeper valve pockets in our Mahle forged pistons, then angle-mill the Dart heads. This will allow us to achieve a compression ratio of just over 11:1 with plenty of piston-to-valve clearance-even if we use our Jesel beltdrive to advance or retard camshaft timing.
Knowing how critical the machining process is, and the complicated nature of what we wanted to achieve, we elected to use what we believe to be the best high-performance machine shop in central Florida, Auto Performance Engines. While the shop is not the least expensive in our area, owner Kevin Willis knows his stuff, replaces tooling regularly, and isn't scared to tell us if something isn't correct. Follow along now as APE performs the necessary steps to get our engine pieces ready for final assembly. And be sure to tune in to a future issue, as we put our LS7-killer small-block together, bolt it to the dyno, and see if we've achieved our goal of exceeding the LS7's 505hp rating.
Auto Performance Engines (APE)...
Auto Performance Engines (APE) installs the main caps and uses torque plates to simulate the presence of cylinder heads during the cylinder-machining process. This ensures that the block is under the same stresses it will experience once it's assembled and running. We consider this the only way to properly size cylinders in a performance engine, so if your shop doesn't use torque plates, you might want to go elsewhere.
Another important consideration...
Another important consideration is the roughness, or grit, of the hone. This is determined by the type of piston ring that will be used. APE has lots of hones for many applications, and chose the ideal one for our application. This will ensure that our rings seal precisely to the cylinder, creating a good seal with minimum friction.
With the engine mocked up,...
With the engine mocked up, the bottom of the cylinders can be marked for connecting-rod clearance. This step is necessary since we're increasing the stroke of our small-block to 4 inches with a Scat lightweight forged crankshaft from Summit Racing Equipment.
The Dart block is designed...
The Dart block is designed for either wet- or dry-sump oil systems. Since we'll be running a wet-sump system, we had to machine provisions for the oil to drain back to the pan. This was accomplished by notching the valley, then drilling holes in the rear of the valley, away from the majority of the rotating assembly.
We'll be using a Jesel beltdrive...
We'll be using a Jesel beltdrive system to drive our camshaft...
...so we needed to perform...
...so we needed to perform a couple of minor modifications to the front of the block for clearance. The beltdrive offers many advantages over a timing chain, which you'll see on the dyno. This is a definite advantage over the LS engine, as the oil pump of the LS makes using a beltdrive system impossible.
You can tell a lot about a...
You can tell a lot about a machine shop by how clean it's kept, and the APE shop is as clean as they come. Once the machining processes on the Dart block were complete, all the pieces were thoroughly cleaned and prepped for assembly.
We ordered our block with...
We ordered our block with the option of 50mm roller cam bearings. This allowed us to take advantage of the larger-diameter camshaft core, eliminating torsional flex of the cam for more-accurate valve timing. The camshaft is also in a raised location, so we can use shorter pushrods for less flex.
The roller bearings use a...
The roller bearings use a special installation tool, which APE has in stock.