When it comes to unpopular engines, the Mopar 361 is one of the kings of the ugly contest. Packing small-block cubes in a big-block envelope, the 361 was introduced in 1958 with a bore of 4.125 inches and a stroke of 3.375 inches. Production continued in truck and industrial applications through to Chrysler terminating big-block production in 1978. In all fairness, in the early to mid-1960s, notable performance versions of the 361 were available. However, in today's world of big-inch big-blocks, the 361 is an orphan abandoned by even the most dedicated Mopar fans as the basis for a performance build. To most enthusiasts, the Mopar 361 is considered a throwaway big-block.

Buck and Clark Hinkle of Hinkle Performance took the unlikely step of considering the 361 as the basis for a true performance street build. Why? As Buck tells us, "I had a few of these lying around, and I just like doing things that are a little bit different." Looking at the basic configuration, Buck recognized the unseen potential. With a 4.125-inch bore, the cylinders are as big as a Chevy 400 small-block, while the 9.98-inch deck height allowed plenty of room for the stroke to grow from its short factory specification. Buck and Clark could see the possibility for building a low-buck performer out of Chrysler's neglected big-block. Hinkle Performance's approach to building this low-deck Mopar was anything but conventional.

Adding Inches

With the aim of adding displacement, the obvious first step was to increase the crankshaft stroke. While there are plenty of off-the-shelf stroker cranks available for the low-deck Mopar B-series big-block, Buck once again went in an unexpected direction. Eyeing the factory forged crankshaft, he determined that the low-buck approach would be to offset-grind the factory 'shaft, taking the original 2.375-inch journal diameter all the way down to the 2.00-inch small-journal small-block Chevy size. As Buck explains, "I was shooting for a stroke of 3.75-inch, looking for the bore and stroke of a 400 Chevy small-block. I figured I could get very close to that using the original crankshaft and ended up at 3.74-inch, which is pretty close." Buck didn't stop there; he went on to grind the main journals down to the 2.45-inch small-block Chevy spec. Buck's clever crankshaft machining created something from nothing—in the best hot rodding tradition. The result is a forged crank providing dramatically reduced bearing diameters for lower bearing speed and friction while achieving the targeted stroke increase.

Back to the block, Buck line-bored a set of Mopar bearings to serve as bearing spacers to use small-block Chevy Clevite main bearings. The modifications in the mains went further, with Buck designing and machining his own cross-bolted main bearing arrangement using the factory 361 caps as the basis. Buck flat-milled the caps and fabricated bridge supports precision-machined to fit across the Mopar block's deep-skirted crankcase. Again, Buck's machining skills and innovative thinking dramatically increased the bottom end rigidity for the cost of a few hunks of steel bar stock and the bolts. The one-off cross-bolted bottom end is the way Chrysler should have built it.

While the small-block Chevy rod journals might suggest that Buck would use aftermarket small-block Chevy rods, he actually went with an Eagle rod manufactured to fit the Ford 5.4 mod motor. He explains, "I wanted a long rod to keep the compression height of the piston down, so I made these Ford rods work. They are 6.657 inches long, which is about perfect. I took a set of the Ford bearings and made them into spacers to take the small-block Chevy bearings; the machining here is critical to maintain the correct fit and crush. On the small end, I took out the pin bushings and ran the pin steel on steel. Without the bushings, the pin hole just needed a small amount of honing to take a small-block Chevy 0.927-inch pin."

Although the engine could actually be built with very low-cost, off-the-shelf Chevy 400 pistons, Buck had custom pistons made by BRC at 0.060 inch oversize. This puts the bore at 4.185 inches, resulting in a displacement of 412 ci. The custom pistons feature low-drag metric 1.1mm compression rings and 3mm oil rings. Buck's 361 was now looking like a thoroughbred with a very low-friction bottom end, respectable displacement, and the added strength to go the distance.