Installing the four-bolt caps...
Installing the four-bolt caps begins with bolting them in and torquing them to spec at the original inner holes. Be sure the mating surfaces are perfectly clean, and install the caps with the bearing locating tang at the same side as on the block. Use extra care to ensure the center thrust bearing cap is centered fore and aft on the block saddle. The stock caps fit inside the stepped-down area of the main saddles, while the Milodon caps extend outward for the angled outer bolts in the web area going to the pan rail.
Street-stroker Mopar A-engines are a recent development, but how well they work depends upon the rest of the setup. In mild form, they're great low-end torque makers. In the Nov. '01 issue of Mopar Muscle, we did some porting mods on a set of W-2 heads and found serious airflow, so a plan was formulated to build an all-out combination to let them breathe in the real world.
Building a stock or mildly modified engine is easy. Just clean everything up, lay out the replacement parts, break out the wrenches, and put it together. However, the more you deviate from the factory plan, the more involved the buildup gets. Before we assembled our engine using one of Mopar Performance's stroker cranks, we selected a 360 block as a base. We located and bought a premium early casting from a junked '72 commercial van, which turned out to be a virgin core with little wear-the perfect foundation for a big-inch buildup. We already assumed that some custom block work would be required.
Beyond the basic stroker clearancing, we went with several mods to the block looking for greater durability, including a set of four-bolt mains. Other changes were required to work with our choice of performance components. The actual building can't start until the grinders, drills, and taps are put away, so we mocked-up where we had to fit it together and went to work. We will cover the block prep this month and begin our buildup story in the next issue of Mopar Muscle.
Adjusting the clearance is...
Adjusting the clearance is done by parallel grinding the cap's inner pad, which brings the cap down until the outer pad is at the correct clearance.
The caps are made with extra...
The caps are made with extra clearance in the outer step area, so they can be sized for an exact fit to the block. Milodon recommends .002-.003-inch final clearance between the outer wings of the cap and the block web. These started out with .008-.010-inch clearance in our block.
The caps were brought down...
The caps were brought down in small steps, until trial-fitting had the clearance set at .002 inch.
Drilling the outside bolt...
Drilling the outside bolt holes can be done on a mill, however, we used a hand drill and the drill bushing supplied by Milodon, as suggested in the instructions. The holes should be drilled just deep enough for full-thread engagement and no more. We went to 1.060 inches to the point of the drill. We set up a stop on the drill bit at exactly the right depth. Occasionally, the new bolt holes can break into the water jacket or out the web rail, but on our block, the bolt holes were well into solid metal all around.
The drilled holes are tapped...
The drilled holes are tapped to 3/8-inch UNC for the outer angled bolts, using the cap as a tapping guide for alignment. Tap first with a standard thread-cutting tap, then follow up with a bottoming tap to get threads all the way to the bottom of the hole. Make sure the thread engagement is sufficient.
Next, the holes were slightly...
Next, the holes were slightly chamfered to ensure no wayward metal or threads will hang up the cap on final installation.
We took the block with the...
We took the block with the caps installed to Tom Rice Machine in Pasadena, California, for the align boring. The aftermarket caps have a lot of extra material in the bearing bores, necessitating substantial metal removal. Here it's critical to have material removed from the cap side only so the crank-to-block centerline doesn't change; use a highly recommended machine shop.
We were particular about the...
We were particular about the quality of machining for our 408-inch stroker. Doing it right requires the right equipment. JGM is equipped with this Rottler milling machine with a block indexing fixture, which ensures the decks are cut parallel to the crank centerline and indexed at the correct 45-degree angle to the centerline established between the crank and the cam bore centerlines. The piston, rod, and crank assembly is measured and the block then decked to give a zero deck height.
With the decks cut, the head...
With the decks cut, the head bolt holes need to be chamfered to keep from pulling out the top thread and minimizing the possibility of distortion at the top of the bolt holes, which could hold up the head and compromise the head-gasket seal.